Originally Posted by PM from 5-90

The RENIX TPS output is not an absolute, neither are absolute resistance readings necessary in the TPS proper.

TPS output voltage should be 17% of input voltage, I will invariably use the manual transmission test outlined in the FSM (1990 FSM p. 8D-33.) This works on vehicles with the AW4 as well, and I consider it to be more reliable than the procedure for the automatic - since the automatic uses the "transmission side" to test, and the automatic TPS is two sensors in one body, a "good" test on the transmission side is not necessarily a "good" test on the engine side. And the engine side is more important.

Begin by measuring the input voltage to the TPS, between pins A and B on the three-pole cnx. Should be ~5.0VDC (experience shows that 5.0VDC +/- 0.5VDC is about right, so 4.5-5.5VDC. It's a regulated supply, and regulators do deteriorate with age.)

Calculate 17% of the input voltage. For correct 5.0VDC, that would be 0.85VDC. For, say, 4.83VDC, that becomes 4.83 x 0.17 = 0.8211VDC. (Yes, use a digital voltmeter, unless you're very experienced with an analogue and have one known to be reliable. It's that important.)

Backprobe pins B and C (positive lead in C) and read output voltage at closed throttle. Loosen the two screws, adjust to reach the figure calculated earlier (17% of input.) Hold the TPS in place (usually, pressing with your thumb will do) and tighten the screws to retain the adjustment. I like to dab a bit of fingernail enamel on these screw threads as an ersatz threadlocker - it has a few advantages:
- It's actually less strong than even LocTite #222, so you don't risk snapping off the screws
- It's just as waterproof.
- It does a better job of coating the threads.
- It may be "gently broken" to allow for adjustment, and will retain the screws without needing to reapply.
- You have a longer initial work time.

However, it is vital that you not use a fixed value for calibration - it is only 0.85VDC nominal output if the reference voltage signal supplied is 5.0VDC! A reference voltage of 4.5-5.5VDC is considered "acceptable," I'd start thinking about a replacement ECU below 4.25VDC.

Any main ground should experience a resistance of less than two ohms (good condition) or even as much as ten ohms (average condition) between that point and the ultimate ground point (battery negative terminal,) depower circuit to measure this. (Removing the battery positive lead is typically sufficient.)

For a function test of the TPS, an analogue ohmmeter is required. Absolute resistance values are not necessary, nor are they given.

What you do is you disconnect the three-wire plug, connect in to the TPS side for pins A & C or B & C, and then slowly and smoothly sweep the wiper arm on the sensor. The resistance reading should vary smoothly as you move the wiper arm - adjust your ohmmeter range setting until you get a reading that makes sense and varies with the position of the wiper arm. You can not use the typical DMM for this test, as a DMM has buffer circuits inbuilt into it that will work to stabilise a reading - and cause a delay in showing a reading change. Analogue ohmmeters do not have buffer circuits, and respond instantly (to demonstrate, set a DMM and an analogue multimeter to the 200VAC range, and connect both to a house outlet. You'll probably see the needle on the analogue waver slightly, while the digital tends to "seek." The analogue response is instant - and knowing this is the first step toward using an analogue multimeter correctly for diagnosis and troubleshooting. I've been using them for thirty-odd years, so I've gotten used to it. I ignore it if I don't need to know, and process it if I do. I've never gotten rid of my analogue, so I have an analogue and a digital handy.)

TO MAKE BACKPROBE PINS:
- Go to your wife's/girlfriend's/SO's/mother's sewing kit.
- Find the two longest, heaviest straight pins in there (quilting pins are good, hatpins are better.)
- Ask for them nicely. (If you end up having to, just go to the craft store and pick up a packet.)
- With a stone (like you'd use to sharpen a blade,) blunt the point of the pins. You want to round it off nicely with no burrs - the lack of burrs will help to preserve insulation and seals. You should be able to press the tip against your skin without penetrating.

The pins slide in the backside of the connector alongside the wire, so you can take a reading without disconnecting (which sometimes eliminates the possibility of taking a useful reading.)

Backprobe pins may also be purchased at electronic supply houses, but they're cheaper to make and easy enough, and you can make a dozen or so for less than what purchasing two would cost. Just don't let the metal bits touch once you've got them inserted - I've made a set and found heat shrink small enough (in various colours) to have a set of a dozen or so that are colour-coded - I used floral pins (about 2m/m thick, about 3" long) and left the 3/4" or so nearest the point uncovered. The heat shrink was cut short enough and located so that I can attach a small crocodile clip or a five-way test lead clip directly to the pin shaft, but the rest of the exposed metal is covered (and the heat-shrink helps to colour-code the things so I can keep them straight on sight. I should probably start making more sets...)

Originally Posted by 89Laredo

Dont probe the square one, probe the flat 3 wire connector.
The square is for the trans and is not nearly as sensitive or important as the ecu side.
Follow the directions for a manual trans.