Engine/Transmission (1994 - 1998) Testing a TPS

[AWray]

How do you test a TPS to see if it is good? Does it need to be installed on the truck or can you bench test it? My trans has had a periodic problem with the torque converter locking and unlocking.

 

[tgrfan2]

TPS

You can do a search and find out more than you want to know. Some problems are caused by electronic "noise". I was lucky on my 95. I started having a problem at 115K, but I have sprayed it down with WD 40 every oil change and have not had the problem reoccur in months. I have never had the problem on the 98 12V with 126K.

 

[LHallmark]

Yes you can bench test it... . It does NOT have to be installed on the truck. It is a variable resister... . a rheostat or potentiometer. Use an OHM meter and measure the resistance between two of the contacts. The two end contacts should read about 2000 OHMS. Reading from the center contact to either end should be variable by turning the center pivot, Readings here should vary from at/near zero to the max value of the resistor. As you rotate the center pivot the resistance should vary smooooooothly.



Once installed on the truck use a fine paperclip to make contact with the center electrical contact and measure the voltage with the ignition on(Engine not running). The output from thte TPS should be 1volt +- . 2 volts. ( . 8 to 1. 2) try to adjust to the high side of that. Once that value obtained, open the throttle fully and the voltage should be about 2. 2 to 2. 8 volts higher than the idle setting... .....



The spray with contact cleaner works well most times.

Good luck with the checks.

 

[Andy Redmond]

An analog vs digital voltmeter works better, it will often detect a spike instead of the "smooth" progression previously described. If it has a spike there might be your dead spot.



If your brave many have disassy'd w/ a dremel or similar and cleaned and relubed.



I like contact clr on the back side once in a while while an assistant moves the throttle for you.



Good luck

Andy

 

[Bob4x4]

An intermittant failure of the brake light switch,or trans temp sensor can give you the issue.....



Bob

 

[AWray]

Thanks for all the tips.

 

[CaptainEric]

I am currently fighting this same problem, torque converter unlocking/locking up to 50 MPH. Above 50 MPH it is ok. PCM was flashed 2 years ago for this same problem. It worked up until now. Dealer has had truck 2 days and cannot find source of problem, other than to say it is electrical related.



Are there any other areas besides the PCM and TPS that may cause the problem. I have the truck right now and am going to disconnect all the electrical accessories that I have added just to rule them out as adding to the problem.

1998 24V 48RE 3. 54 axle

 

[Andy Redmond]

You probably have the 47RE. . ? unless the org. unit has been updated to the 48RE.



Good luck

Andy

 

[CaptainEric]

Sorry, finger check and wishfull thinking. It is a 47RE.