(22RE, 22REC, 22RET, and the 3VZx variants)
If you have come here, you are either having problems with your TPS reports:
What's happening?
Uh... we have sort of a problem here.
Yeah. You apparently didn't put one of the new cover sheets on your TPS reports.
Mmmm... yeah.
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.
Fun Fact: In the movie Office Space, TPS was an acronymn for Test Program Set which is a real document that describes testing procedures for software programs.
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 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 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.
Pictured above:
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.
Length: Select length: 16 mm (default) 12 mm
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:
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!
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.
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 to):
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.
In the above tests, you are actually simulating various throttle positions and rotating the TPS on its base to achieve all the above conditions.
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 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.
Symptoms of a bad or misadjusted 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 engine.
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.
Visitor # 678781 since 18.MAY.2002
[Last updated: 20.June.2020]