The Toyota 22R-E and 3VZ-E engines are electronically fuel injected. As
such they lack a mechanical carburetor and instead split the function
of the carburetor into three parts, namely the Air Flow Meter in the air cleaner box,
the throttle body and the fuel injector. The air flow meter uses a
flapper vane and temperature sensor to detect the temperature and
velocity/flow of the incoming air charge. The throttle body controls
the air flow into the engine and the fuel injectors supply the proper
amount of fuel to each piston depending upon operating conditions.
While this information is based upon the TPS system in the 22R-E
engine, most of it applies to other Toyota EFI engines. For specific
information, be sure to consult the service manual for your model
engine.
The Toyota 22R-E (and R-EC) engines use a "Linear" throttle
position sensor. The sensor basically looks at idle or closed throttle
(IDL) and throttle angle opening (VTA). The TPS itself is simply a
linear variable resistor that when driven by the ECU produces a linear
voltage in a 0-5 volt range, 0 volts being idle and up to 5 volts
representing throttle opening angle. Internally, there is also a switch
that detects the idle position.Proper adjustment of the TPS is critical
for engine performance, fuel economy, and emissions. An improperly
adjusted TPS effects many other inputs and outputs from the ECU, many
of which would not even logically point to the TPS. Aside from being
out of adjustment, the TPS can just plain wear out or break internally.
Periodically, the throttle body should be cleaned or checked for a
buildup of sludge that may clog the air bypasses, vacuum ports, or
prevent the throttle plate from closing to it's proper position. This
should be checked prior to any adjustment of the TPS should a trouble
code relating to throttle position appear during a self-diagnostic
test. Crankcase vapors are commonly vented into the throttle body for
re-introduction into the combustion process (by the Exhaust Gas
Recirculation, or EGR, valve). These vapors can leave an oily residue
on the back of the throttle pate and allow sludge and dirt to
accumulate. The throttle body can easily be cleaned while on the
vehicle with a little carburetor cleaner and a cloth. However, for
heavy sludge buildup, it should be completely removed, washed in
solvent, and dried thoroughly. When doing this, it is important that
the TPS should be removed to prevent contamination (a primary cause for
failure) and the throttle body-to-plenum gasket replaced.
The TPS is adjusted by means of rotating it slight with respect to the
throttle body itself. To check the TPS, first unplug the connector from
the sensor, then using a thickness gauge between the throttle stop
screw and the stop lever, use an ohm meter (see Figure
3)to check the various terminal-terminal connections for proper
resistance values (see Table 1). Obviously, these
tests are done with the engine not running.
We now offer a quality metric feeler gauge set that allows all the
various throttle stop gaps to be set with one or two shims in various
combinations.. It has 0.04-0.09mm shims in 0.01mm increments plus
0.10-1.00mm in 0.05mm increments. Cost is US$22.00 plus domestic US
postage (only). Also have added a deluxe TPS screw kit with the
stainless steel screws, ball-end allen key and the metric feeler gauge
for US$30.00 plus domestic US postage (only). We assume customers
outside the US can acquire metric feeler gauges locally.
-
Notes:
-
Dash Pot:
-
The GREEN CIRCLE shows the dash pot (DP)
which is there to slow the closing of the throttle to prevent
backfiring. It consists of the round air bellows, a spring loaded
plunger, and the air vent line that attaches to the fitting at the base
of the bellows. The vent line has a check valve in-line and an air
filter to keep dirt out. The check valve lets air into the bellows then
the throttle opens and extends the plunger. When the throttle closes,
the stop screw contacts the plunger and pushes it in. The check valve
closes to slow the air escaping the bellows and thus slow the closing
of the throttle.
-
To troubleshoot the DP, make sure the air filter is clean and make sure
the check valve is not clogged or stuck open. You should be able to
blow air into the bottom easily (filling the bellows) but it should be
hard to suck air out. Both the filter and valve can probably be cleaned
with a mild solvent. Also, the plunger can stick. I find a shot of
silicone spray applied to it periodically helps keep it moving freely.
Lube it the push it in and out fully a few times to work the lubricant
down into the plunger. And you can simply back the adjuster screw all
the way back to keep it from contacting the throttle linkage as a test.
This way it is eliminated from affecting the throttle operation, in
case you think it may be causing a problem.
-
To adjust the DP, I find setting the stop screw to depress the plunger
about 1/2 of it's travel works well. If set too deep, you have more
spring force to overcome and that can cause the throttle to not fully
close. Too shallow and the DP can't really do it's job.
-
Throttle Stop Screw:
-
The other item that scan affect the TPS adjustment is the Throttle Stop
Screw. The stop screw controls the amount of closure for the throttle
plate inside the throttle body. It must be set properly BEFORE
adjusting the TPS itself. How is this done? The stop screw is set so
that the throttle plate is fully closed inside the throttle body, then
it is turned in to contact the throttle linkage and then 1/4 turn more
before tightening the jam nut to lock it in place. This is done so that
the throttle plate is held just barely off fully close to prevent it
from sticking inside the throttle body.
The only real problem to adjusting the TPS is that the screws are
nearly impossible to access when the unit is on the throttle body
installed on the intake. To make adjustment easier, you can replace one
or both TPS screws with allen head screws and then use a ball-end allen
wrench to loosen and tighten them. Pictured below are the pair of
metric allen head screws used to replace the stock Philips head screws
and below that is the optional ball-ended 3mm allen key that makes
removal and installation of the screws plus subsequent adjustment of
the TPS easier:
 |
 |
A: TPS Screws and ball end Allen Key |
B: Screw Length Measurement |
If you can't locate the extra fine pitch metric screws, they are
available for purchase below. The first kit is just the two stainless
steel allen head screws. This kit should fit both 22RE/REC/RET 4-cyl.
engines as well as the 3VZE V-6 engine throttle position sensors.
Included with the screws are two washers. In certain applications, you
may find an extra washer or two may be needed in case the new screws
bottom out in the threaded hole in the throttle body. The 4mm dia.
screw length is 16mm, matching the longest stock screw length or also
available in the shorter 12mm length. The second kit includes the
screws and a long-arm ball-ended 3mm allen key which allows for
off-angle access to the upper screw. The lower screw can be accessed
from the side with the thermostat housing removed, or from the front
using the short end of the wrench.
The typical TPS screw is approx. 5/8" (16mm) long from the base of
the head to the end of the threads. This length seems to fit most
applications, but certain years may use a shorter approx. 1/2"
(12mm) long screw, two known years that may have this size are the 1989
and 1990/22RE. If in doubt, remove the upper screw and measure the
length. Or if that is too much hassle, order the standard 16mm screws
and if needed, you can always add a few washers under the longer screw
if needed, as it is easier to make a screw shorter, but it is very hard
to make it longer!
|
|
TPS Screws - US$5.00
with US shipping and applicable sales tax |
TPS Screw Kit w/ Allen Key - US$10.00
with US shipping and applicable sales tax |
~~~~~ |
~~~~~ |
|
|
TPS Screws - US$5.00
with International shipping |
TPS Screw Kit w/ Allen Key - US$10.00
with International shipping |
You'll likely need to either remove the throttle body or at least the
thermostat housing on the 22RE engine to remove the old screws before
installing the new allen screws. You'll likely want to drain a quart or
two of coolant from the radiator before removing either part, save it
for refilling the system later. If the TB is removed, best to set the
TPS while the unit is out, there is more room to work that way. And one
tip for swapping in the new screws without affecting the current TPS
adjustment is to remove one old screw, then install the new screw and
tighten it down before swapping the 2nd screw.
-
Note:
-
If you have to remove the throttle body, no need to drain the cooling
system as the factory service manual suggests, simply insert a bolt or
stopper into the small coolant line that attaches to the throttle body
(keeping the radiator cap in place) and you'll only lose a little bit
of coolant, replace it when finished.
The only real "adjustment" needed is for the IDL-E2 setting,
the rest of the checks are just to verify proper operation. If you are
comfortable using an ohm meter, you may skip the next
section and proceed to the specific measurements, otherwise read
the following section to understand how to use an ohm meter:
 |
Ohm Meter Use |
And shown in picture #5 is the proper ohm meter connection and use. If
you are not familiar with the use of an ohm meter, the following
paragraph will hopefully explain enough to get you started (click on
the above image for a larger version that is easier to see if you need
to):
-
The picture above shows a Digital Multi-Meter (DMM) connected to the
TPS connector.
-
In the WHITE circle, you can see the red probe connected to the VTA
terminal and the black probe connected to the E2 terminal of the TPS
connector.
-
In the RED circle, you can see the DMM Function selector switch set to
the K-Ohm (Kilo Ohms) mode:
-
Note, this may vary on different meters, some have a dial to select
both the reading and range and some automatically select everything for
you. Consult your meter's usage guide for more details.
-
In the MAGENTA circle, you can see how the red probe is inserted into
the Ohm/Amp plug. To see the flow, follow the heavy gray line from the
red Ohm plug, through the pointer on the Function switch to the K-Ohm
Range selector (more on that later).
-
Again, this may vary with different meters, some meters internally
switch the probe connections based upon the Function setting.
-
Why the different plugs on this meter?
-
A meter essentially measures current. A typical meter might read full
scale with 1 mA (0.001 amps) of current flowing through it. So, to
measure current, it is simply a matter of putting the meter in series
with the load and let the current flow through the meter (where is is
measured) and through the load. Range switching is done with shunts to
pull off only a fraction of the load current through the meter. So if
you only let 1/1000th of the current flow through the meter, a 1mA
reading would equal 1.0 amps of real current (0.001 * 1000 = 1.0).
-
Thus the Red-Black plug connection is direct connection to the internal
current meter.
-
To measure DC voltage, you put the meter in parallel with the load and
add a resistor in series with the meter to limit the flow of current.
So, if you put a 1000 ohm resistor in series with the 0.001 amp meter
and put 1.0 volts across the two, you would have 1.0/1000 or 0.001 amps
flowing through the meter. If the display reading were scaled to read
1.0 (at full scale), you would see 1.0 volts, or the proper reading.
-
Thus the Gray-Black plugs make a connection to this internal series
current-limiting resistance.
-
To measure AC voltage, you need to add a diode in series with the meter
to convert the AC voltage to DC so that the digital meter can read a
steady voltage. If the diode were not there to rectify the alternating
voltage, the reading from the meter would just appear to be a random
series of numbers.
-
Thus the Orange-Black plugs make the connection through the internal
rectifying diode.
-
And finally, the resistance (or ohms) function requires that some
voltage source (from the meter's internal battery) is needed to drive a
current through the external resistance and the meter to complete the
circuit. This connection is basically the same as the current measuring
connection (that is why the same Red-Black plugs are used) and when
Ohms is selected, the internal battery voltage is applied to the
circuit. So, if the internal voltage is 1.0 volts and you apply that
across a 1000 ohm resistor, 0.001 amps of current will flow and a full
scale reading of 1.0 (K-Ohms) is displayed.
-
Note that when measuring ohms, there must be no power in the circuit
you are measuring, otherwise you will get either erroneous readings
(due to not knowing the voltage value) or worse you will damage the
meter by forcing too much current through it's sensitive circuits.
-
Then the GREEN oval shows the K-Ohms Range selector in the 20 (K-Ohms)
range. This means that the full scale reading on the meter will be
20.000 (K Ohms) or 20,000 Ohms.
-
Again, this may vary from meter to meter, some meters use an 1X - 10X -
100X - 1000X and so on multiplier that you must multiply the reading by
to get the actual value. So a reading of 20 on the 1X scale is 20.0,
while on the 1000X scale is 20,000.0.
-
So, finally to the reading on the display (circled in YELLOW), which in
this case is 0.81. In order to convert that decimal number to the
proper units, you must traverse the meter settings to get that all
correct:
-
0.81 on the 20K range is the same as 0.81 (K ohms) or 810 and since it
is on the ohms function, the correct reading is 810 ohms.
-
This 20K range is somewhat similar to a meter that had a 1000X
multiplier, thus a reading of 0.81 * 1000 = 810. So it is important to
not confuse ranges and multipliers, since if you interpreted the 20K
range as a 20K (or 20,000X) multiplier, you would be off by a factor of
20!!!
-
Also note that on the 20K range, the least significant digit is only
good to 10 ohms. This as you go up in range, the accuracy/resolution of
the meter goes down. It is therefore important to select the meter
range just big enough to capture the range of values you expect to
read, but no bigger than necessary. For the TPS, resistance range from
about 500 up to 10,000 ohms, so the 20K range is ideal.
 |
 |
Figure 2: Throttle Position Sensor (TPS) |
Figure 3: TPS Adjustment |
Now, on to testing and adjusting the TPS. Table 1 lists the adjustment
specifications for the early (1985-1995) TPS. There are slightly
different measurements for the later model units. If someone knows the
engine date at which the change below took effect, drop me an e-mail.
My guess is the change took place with the change in the throttle
body, early trucks TB is angled downwards, later trucks are horizontal.
Refer to the above figures for TPS terminal layout and ohm meter
connections. If in doubt about the layout of the terminals, an easy way
to identify the proper orientation is to identify the VTA-E2 terminal
pairs. E2 is at one end of the TPS connector or the other. VTA is one
pin in from the opposite end. The VTA-E2 signal varies from a few
hundred to a few thousand ohms as the TPS moves through it's range or
travel. So, try one end of the TPS connector for E2 and see if the
resistance varies properly, if not, try the other end. Once the E2 end
of the connector is identified, the rest of the pins should be laid out
as indicated in Figure 2.
Note: There is some variation in the "exact"
resistance values among the various years, but in general test 1 should
be a low resistance, under 1K (or a few K) ohms. Test 2 is under 2300
ohms, test 3 is open cicruit and tests 4 and 5 will be higher
resistance, fabove 3000 ohms, more or less. Looking at these values,
2300 ohms seems to be the transition point where the ECU switches
between a logic level of 0 and 1. Anythng under 2300 ohms is sensed as
a logic level 0 and anything over 2300 ohms is a logic evel 1. Nor,
right around 2300, things get a bit fuzzy, so that's why the low
resistance readings are generally well below 2300 and the higher
resistance readings are much larger than 2300.
Table 1: 22RE (2.4L-4
cyl) - TPS Adjustment Specifications
- Early model p/n: 89452-20060
- Late model p/n: 89452-12040
Test |
Clearance between
lever and stop screw |
Between terminals |
Resistance /
'85-'88* (ohms) |
Resistance /
'89 (ohms) |
Resistance /
'90*-'95 (ohms) |
1. |
0.00mm (0.000") |
VTA - E2 |
200-800 |
200-800 |
470-6100 |
2. |
0.57mm (0.0224") |
IDL - E2 |
< 2.3K |
< 2.3K |
< 2.3K |
3. |
0.85mm (0.0335") |
IDL - E2 |
Open / Infinite |
Open/Infinuite |
Open / Infinite |
4. |
Wide Open Throttle |
VTA - E2 |
3.3K - 10.0K |
3.3K - 10.0K |
3.1K - 12.1 K |
5. |
n / a |
Vcc - E2 |
3.0K - 7.0K |
4.0K - 9.0K |
3.9K - 9.0K |
Table 2: 3VZ-E (3.0 V6)
- TPS Adjustment Specifications
(*) Some test charts list these alternate throttle openings for
testing
Test |
Clearance between
lever and stop screw |
Between terminals |
Resistance /
'88 (ohms) |
Resistance /
'89-'95 (ohms) |
1. |
0.00mm (0.000")
or 0.50mm* |
VTA - E2 |
200-800 |
200-800 |
2. |
0.50mm (0.020")
or 0.77mm* |
IDL - E2 |
< 2.3K |
< 2.3K |
3. |
0.77mm (0.030")
or 0.85mm* |
IDL - E2 |
Open / Infinite |
Open / Infinite |
4. |
Wide Open Throttle |
VTA - E2 |
3.3K-10K |
3.3K-10K |
5. |
n / a |
Vcc - E2 |
3.0K - 7.0K |
4.0K - 9.0K |
In the above tests, you are actually simulating various throttle
positions and rotating the TPS on its base to achieve all the above
conditions.
-
Test #1 simulates the closed throttle position, with
the throttle valve fully closed and the throttle stop lever in contact
with the throttle stop screw
-
If you can't get this fully closed reading, make sure nothing is
holding the throttle slightly open, like an improperly adjust throttle stop
screw or dirt between the TPS back side actuator and the
throttle body mechanism.
-
If all is mechanically OK, then this reading can ba a go, no-go test,
after all if you can't get a throttle closed reading with the TPS fully
closed, then no amount of adjustment will help, since any adjustment is
adding to the closed (0.00mm) throttle position.
-
Test #2 and #3 test the transition from idle to
normal operation
-
Note that the exact feeler gauge values are not terribly important, use
the closest gauge you have to the value, or stack two thinner gauges to
make one the right thickness. Its unlikely you'll be able to adjust the
TPS by hand to 0.001" anyway (in fact if you can get within
0.01" or 0.1mm you are doing pretty good!).
-
And note that there are a range of values for these tests on the V6
TPS. One might suspect that the "exact" throttle opening
where the IDL-E2 setting changes from below 2300 ohms to infinite makes
little difference. Rather it is the fact that it *does* change and does
so at a small throttle opening (under 1mm or so). Whether that happens
at 0.50mm, 0.70mm, or even 0.90mm probably makes little difference.
-
Setting the TPS idle transition too close to 0 opening may result in a
rough idling engine if the throttle were to stick open a tiny bit.
-
Setting the transition too far out, would result in a sluggish throttle
response, since the ECU would see a longer idle section on the TPS.
-
Note: 0.80mm is about the thickness of a typical credit card, 0.50mm is
about the thickness of a thinner plastic gift card, in case you lack a
set of feeler gauges.
-
So, if your TPS makes the idle transition (below 2300 to infinite) but
you can only get it to do so at say 0.90mm instead of at 0.85mm, for
example, does this mean the TPS is bad? Probably not, if everything
else checks out, you may just be seeing the effect of the mfg.
tolerances of the TPS and the throttle body stacking up and pushing the
setting outside the "normal" range.
-
Now, if the TPS never makes the idle transition (i.e. it reads infinite
at all throttle openings, or it reads < 2300 ohms at all throttle
openings), then likely it is bad.
-
And don't worry if THE GAP is not dead on. There are no "TPS
Police" that are going to pull you over and whip
out a set of feeler gauges to check your IDLe transition point.
-
Heck, even the dreaded California smog tech's don't even look at the
TPS as part of the visual check. As long as the engine is timed right
(which relies on the TPS-IDL setting), that is all they care about.
-
Also, don't get hung up on getting some exact resistance reading.
-
Less than 2300 (2.3K) ohms means just that, anything less than 2300 is
fine; 2299 is less than 2300. 996.5 is less than 2300, 0.1 is less than
2300.
-
Basically any reading in the range of 0.0 to 2299.9 is less than 2300.
If your meter reads less than 2300, that is fine.
-
Test #4 tests the wide open throttle (WOT) setting.
-
And you should see about the same VTA-E2 reading at wide open throttle
as you read on Test #5 (below) on VCC-E2.
-
This makes a good double check of your reading accuracy and
repeatability.
-
Test #5 just measures the entire resistance of the
outer-most current track seen in Figure 2.
-
This reading will be the same regardless of the throttle opening.
-
It can't be adjusted, so is basically a go or no-go reading.
-
If the reading is within the specified range, it is OK, if not, it is
not OK.
-
So, how do you interpret the above test results and decide if your TPS
is good or not? Well, here is how I interpreted the test results on
mine:
-
On my TPS, I measured a value of 500 (0.5K) ohms for test #1 and 5000
(5K) ohms for test #4 and the other values within spec. By setting the
#1 resistance to roughly the middle of the range, the rest of the
settings were dead on. One final test, not listed in the FSM, would be
to run the TPS shaft from idle to WOT and watch the VTA-E2 resistance
and make sure it increases monotonically, no drop outs or dead spots.
If you observe abrupt resistance changes, the TPS could have a burned
area on one of the current tracks. And finally, see the section here for some symptoms
of a defective TPS - and if you do not have those symptoms, then it is
likely OK as the ECU is the ultimate "judge" of goodness or
badness.
See below for a detailed, step-by-step procedure for adjusting the TPS:
-
Loosen both screws attaching TPS to throttle body.
-
Attach multi-meter to TPS terminals IDL and E2 (the bottom two
terminals on the TPS).
-
You can use alligator clips to make this easier or use small
¼" lengths of vacuum hose to hold them on
-
Insert 0.85mm (22RE) or 0.77mm (3VZE) feeler gauge between throttle
stop screw and throttle plate (see picture)
-
Move TPS body CW/CCW until ohms reading on multi-meter is infinite
(open)
-
Move the TPS body very slowly CCW until you find the end of the
resistive strip, the meter will indicate <2.3K ohms of resistance
-
Move the TPS body extremely slowly in the CW direction until the meter
goes to open/infinite again
-
Tighten the top TPS screw being very careful not to disturb the
adjustment
-
Remove the feeler gauge and insert a 0.57mm (22RE) or 0.50mm (3VZE)
feeler gauge
-
The meter should (hopefully) indicate between 0 and 2.3K ohms of
resistance.
-
If it does tighten the bottom screw and reconnect the electrical
connector.
-
If not go back to step 4 and try again
-
To check whether the adjustment was successful start the engine and
insert the timing test jumper.
-
If the idle speed decreases audibly it is working normally.
While the above tests performed at the TPS itself do verify that the
sensor itself it functioning, it does not test the continuity of the
wiring in the harness that ultimately connects the TPS signals to the
ECU. If TPS problems are suspected and the TPS itself checks out fine,
then repeat the above tests at the ECU connector pins to verify they
are reaching the ECU properly.
[Back to the top]
Symptoms of a bad or misadjusted TPS include:
-
Inability to correctly set base ignition timing:
-
Varying idle speed, unstable idle or even misfiring at idle:
-
This can happen because if the IDLe-E2 contact closure is not detected,
the ECU is "running the engine real slow" vs. entering the
stable idle mode. At low RPM and load, all the typical ECU sensor
inputs may not be accurate and the ECU is trying to guess what is going
on and adjust engine parameters on the fly. In normal idle, the ECU
likely has a sort of pre-programmed loop it enters and ignores a lot of
the sensor "noise".
-
Note that a low coolant level can affect this as well, if air pockets
reach the temperature sender, the ECU can get false readings of engine
temperature and alternate between cold and warm idle speeds.
-
Hesitation while accelerating:
-
Poor fuel economy:
Seemingly unrelated systems can also be affected by a malfunctioning
TPS, including Electronically Controlled Transmissions (ECT). Problems
can include poor shifting and hunting between gears due to the engine
computer seeing apparent throttle position changes coming from a flaky
TPS. Since it is the TPS that tells the engine's ECU that you are idle,
if that setting is off, setting timing can be difficult, since
insertion of the timing check jumper won't have any affect on the
engine.
And it is this very simple test that can be the ultimate test of the
idle circuit of the TPS. If the ECU responds to the timing test jumper
as it should with your TPS connected, it is "good" per your
ECU. It is not like the ECU is sitting there with an ohm meter and if
it sees 800.1 ohms on the IDL-E2 circuit, it won't recognize the idle
signal. Likely there is some slack in the resistance ranges Toyota
publishes. They are basically saying that anything less than 800 ohms
will always work, but it may work above 800 ohms but it is not
guaranteed. So if it works, great, if not, get a new TPS.
So, how does a TPS fail? Most likely one of two things will cause a TPS
to fail. If you look inside one, you'll see it
basically consists of a printed circuit board with a combination of
conductive and resistive strips in a circular pattern, over which wiper
contacts slide. This serves to generate the various resistance readings
at varying throttle positions. The usual failure is for what used to be
a low resistance to become an open connection (i.e. infinite resistance
or ohms on a meter).
Upon visual investigation, its usually the case that the contact area
on the PC board is burnt or dirty, leading to the open circuit reading.
Putting too high a current through the TPS circuit (possibly due to a
short circuit in the engine wiring harness) could lead to contact
burning, but more likely is that a foreign substance entered the TPS
and initiated the problem. A common cause of this is using throttle
body cleaner in the throttle body without removing the TPS. The cleaner
can wick into the TPS via the actuator that rotates the TPS. The
cleaner can attach the PC board and components and cause it to fail. If
cleaning the throttle body, be sure to remove the TPS, and also try to
avoid getting engine cleaner and water on the TPS, its not totally
sealed.
When re-installing the TPS, one handy tip is to replace the stock
screws with allen head screws, the you can use a ball-headed wrench to
access the screws while the throttle body is in place. Another tip for
removing the throttle body is that if you keep the radiator cap on and
use a bolt to plug the coolant hose that connect to it, there is no
need to drain the cooling system as the Factory Service Manual
recommends. You may lose a few ounces of coolant, but its no big deal.
If the TPS checks out fine, but you still suspect TPS problems, you
should also check out the TPS connections to the ECU itself. You can
have a perfect TPS, but if there is a wiring problem between it and the
ECU, there will still be a problem.
And the way to ultimately test this out is to look at the TPS the way
the ECU "sees" it. That is with the resultant voltages that
appear at the ECU inputs while the engine is running. Why not do these
tests first? Well you could, but they are harder to do since you need
to hook up wires to sample ECU input signals and then monitor them with
the engine running, or at least with power applied to everything (i.e.
the ignition on). But the FSM lists the test points and voltages you
should use and how to interpret them. But the basic jist is to measure
the voltage at VTA to ground (see connector pin out below) and observe
that voltage over the range of throttle positions. At idle, you should
less than 0.5 volts and it should smoothly increase to about 5.0 volts
at wide open throttle. And the IDL to ground voltage should be near 0
volts at idle and close to the battery voltage at anything off of idle.
And you can use this 0V to 12V transition point to adjust the IDLe
setting on the TPS. Of course, this is most precise but also the
hardest to do since you are checking the voltage from inside the
passenger foot well and adjusting the TPS in the engine bay, so unless
you have a trained helper, it is not the easiest way to proceed. If you
are having suspected TPS-related issues while driving, you might
consider hard wiring up some test points off the ECU and then setting
up a volt meter in the driver's compartment to observe or even fancier,
set up a data logging system with a laptop and record the signals and
look at them closely at a later point.
ECU Connector Pin outs (TPS connections in BOLD)
E01 |
No10 |
STA |
Vf |
NSW |
E01 |
No20 |
IGt |
E1 |
n/c |
|
Fpu |
W |
T |
IDL |
IGf |
n/c |
n/c |
KNK |
Ne |
ACV |
n/c |
TSW |
n/c |
E2 |
Ox |
Vcc |
VTA |
THW |
|
n/c |
n/c |
Vc |
Vs |
THA |
BATT |
+B1 |
n/c |
n/c |
E21 |
4WD |
SPD |
B/K |
+B |
|
Pin |
Input/Output |
Connects To |
Description |
E01 |
. |
. |
. |
E01 |
. |
. |
. |
No10 |
Output |
Fuel Injector |
Grounding Connection |
No20 |
Output |
Fuel Injector |
Grounding Connection |
STA |
. |
. |
. |
IGt |
. |
Ignitor |
IGt signal |
Vf |
. |
. |
. |
E1 |
. |
. |
ECU Ground connection, shared with ignitor |
NSW |
. |
. |
. |
n/c |
n/a |
n/a |
Not Connected |
Pin |
Input/Output |
Connects To |
Description |
Fpu |
. |
. |
. |
ACV |
. |
. |
. |
W |
. |
. |
. |
n/c |
n/a |
n/a |
Not Connected |
T |
. |
. |
. |
TSW |
. |
. |
. |
IDL |
Input |
TPS |
TPS IDLe contact |
n/c |
. |
. |
Not Connected |
IGf |
. |
Ignitor |
Ignitor IGf signal |
E2 |
. |
. |
. |
n/c |
. |
. |
Not Connected |
Ox |
Input |
Oxygen Sensor |
. |
n/c |
. |
. |
Not Connected |
Vcc |
. |
. |
. |
KNK |
Input |
Knock Sensor |
. |
VTA |
. |
. |
. |
Ne |
. |
Ignitor |
Ne signal |
THW |
. |
. |
. |
Pin |
Input/Output |
Connects To |
Description |
n/c |
n/a |
n/a |
Not Connected |
n/c |
n/a |
n/a |
Not Connected |
n/c |
n/a |
n/a |
Not Connected |
n/c |
n/a |
n/a |
Not Connected |
Vc |
. |
. |
. |
E21 |
. |
. |
. |
Vs |
. |
. |
. |
4WD |
Input |
4WD Switch |
In transfer case |
THA |
. |
. |
. |
SPD |
. |
. |
. |
BATT |
. |
. |
. |
B/K |
. |
. |
. |
+B1 |
. |
. |
. |
+B |
. |
. |
. |
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Visitor #
697896
since 18.MAY.2002
[Initial creation: 24.Jan.2000]
[Last updated: 13.March.2021]