(22RE, 22REC, 22RET, and the 3VZx variants)
If you have come here, you are either having problems with your TPS
Uh... we have sort of a problem here.
Yeah. You apparently didn't put one of the new cover
sheets on your TPS reports.
You see, we're putting the coversheets on all TPS
reports now before they go out.
Did you see the memo about this?
Yeah. If you could just go ahead and make sure you do
that from now on, that will be great.
Or your Throttle Position Sensor:
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
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
The throttle body (Figure 1) contains the
throttle valve that it operated by the accelerator pedal in the
driver's compartment. The valve serves to regulate the amount or air
that gets introduced into the engine. The fuel injectors spray atomized
fuel into the intake of each cylinder in response to an electrical
signal from the engine computer (ECU). One determining factor (among
many) for the amount of fuel to inject is based upon the position of
the throttle valve. This position is determined by the throttle
position sensor (TPS).
So why test it? Well, assuming you are having an engine-related
issue that you think might be due to the TPS (see troubleshooting section for common symptoms),
then it makes sense to test the one you have first. Why?
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.
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 easier:
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 (black oxide screws, not stainless
steel). 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 use a shorter approx. 1/2" (12mm)
long screw, one known year is the 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!
16 mm (default)
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.
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:
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
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 fropm 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.
In the above tests, you are actually simulating various throttle
positions and rotating the TPS on its base to achieve all the above
See below for a detailed, step-by-step procedure for adjusting the TPS:
While the above tests performed at the TPS itself do verify that the
sensor itself it functioing, 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.
Symptoms of a bad or mis-adjusted TPS include:
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
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 reistance 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
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 pinout 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 tranied 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.
[Last updated: 04.March.2013]