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TPS testing with no connector

tripletsjeepin

NAXJA Forum User
Location
Montana
Ok I have read many post about testing the TPS. They say to use the square connector and use the letters on the connector to identify which one to use. The problem I have is my connector is gone and the TPS is hardwired in.... (vehicle was totaled and fixed) Where can I find what wires to use. 88 cherokee, AW4 4.0 Liter.
 
This shouldn't be too hard. Of the three wires, one is ground, one is supply voltage, and other is signal voltage back out. Voltages are under 5.0v. Use your multimeter on voltage setting (range something like up to 20 volts-- not 1000 volts!!), engine running, take a reading between each wire and a good ground. The one reading zero or a fraction of a volt is the ground. The one reading around 4.8v. is the power in. The one reading around 85% of the number for power in (85% of about 4.8 v.) is signal out. This is for an auto transmission- standard may have a different % voltage output--will be a reduction from the input voltage). If you are calibrating the TPS, then compare the voltage between the power in and ground wire to the voltage between the signal out and ground wire. From my file:
Lets go back to that voltage at closed throttle.
Manual Transmission TPS all readings from ground (B)
A 4.75-5.0volts
B ground
C .85

AW4 Automatic Transmission TPS all readings from ground (B)
A 4.75-5.0 volts dc.
B ground
C 4.14 volts dc
As you can see Manual and Auto are opposite.
Manual starts low and goes high and Automatic is High and goes low.
 
IN case it is not clear from the above post, the TPS for an automatic actually has two separate sections, where the manual has only one. ONe section is wired to the engine computer and the other to the TCU. When you test the one for an automatic you use the TCU section, and that is why the readings are different. If yours is hard wired, you'll first have to make sure you identify the correct section. I am not at home or anywhere where I can look at the thing or a picture of it, so I can't readily tell you which section is which. You may have to trace the wiring. Perhaps one of the Renix experts can supply the details. I hope I'm not imposing, but suggest that if you can't figure it out, you PM 5-90, who has done a lot of tinkering with these things.
 
I found my 1988 Factory Service Manual PDF: on the connector that leads to the Transmission Control Unit, black wire is ground (connects to tan/orange), blue wire is signal to TCU (connects to gray/tracer) and grey is power in (connects to red). On the connector that goes to the Engine Control Unit, light blue is terminal A with 5 volts supply, brown/tracer is terminal B ground and yellow/green is terminal C signal out to ECU.
 
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