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Another TPS ?????

1244 Views 9 Replies 2 Participants Last post by  bharner
OKay I've searched the posts and read the FSM many times but am still confussed about checking the tps. I retract the ISC plunger and disconnect. I remove the TPS connector and check the voltage but every combo gives me -0.00 volts. The FSM says to use some sorta harness to check with DVM but I dont have that of course. I guess I'm asking,by disconnecting the TPS jumper is that not gonna give me a valid read out. Do I need to leave it connected and probe thru tha wires? Also wat terminals of the TPS do I check. I'm guessing (-) ground/where the blk/pnk wire plugs into the TPS but wat about (+). I've tried where the blue and the grey wire connect but still nada. ??????
Thanks guys.
92 Deville 4.9nr
I have a DVM I dont have the Jumper harness
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If you don't have a DVM and don't want to buy one, I bet your local rent-a-center may have one to rent for a few bux. Or, borrow one from a friend. Or, try your local Autozone or Napa autoparts store. They may loan or rent you one.
I have a DVM. I dont have the Jumper harness. I guess can the TPS be checked accuratly with the TPS harness disconnected?
I keep getting an E26 Code. Shorted Throttle Switch Signal. I have testd the ISC multiple time but it keeps passing so I'm thinking it might be the TPS but not sure if I am testing correctly.


Also ISC Full Extension reads -0.00 volts. So I think I'm testing incorrectly. Any info would be helpful as I am trying to solve intermintent cut off problem
Run the PCM switch test. See page 6E-5 in the FSM. The Throttle Switch is part of the ISC (see "E.7.2 Throttle Switch" on same page).

FYI, see "TPS Adjustment" in section Page 6E-C2-16.

If you're sure that the ISC is ok (sounds like you are), then replacing the TPS may be in order; however, according to the FSM, it could be bad contacts, a short, an open, or a bad PCM.

Did you go through the entire fault tree on Page 6E-A-63?

You mention that the FSM says to use some sort of test harness. You may have read that wrong. I think the part you're referring to says:

- TPS Disconnected
- connect a voltmeter ........ in TPS harness connector

I think they're saying, "connect a voltmeter bewteen Pin B and Pin C in the TPS harness", not some separate test harness.
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like i said I test the ISC multiple times. passes E.7.2 everytime. checked for intermintents nada.

Are u sure u got the same FSM as me. 92-93 Deville

Page 6E-C2-16 TPS ADJUSTMENT Paragraph 4. "With the engine running at the minimum air RPM setting, check TPS voltage using TPS jumper harness tool J 38490 and a DVM"

I'm getting aprx 5 volts from PCM thru the harness from the PCM so I'm looking for a faulty TPS. But when I attempt to test I'm getting -0.00 for both fully retracted and extended ISC. With the TPS disconnected and the manual shows that u are to test the TPS with this special harness(J 38490) so I'm guessing I'm to test with it connected, just trying to find someone here that has successfully test their TPS. Did u disconnect it b4 testing it? Anyone out there who has actually done this???? Thanks yall
Yah, I got the 92/93 Deville FSM. I wonder if we have two different printings. Hmmmm.....

Sorry, I'm at a loss what to do next.

When I tested it, it was such a long time ago, I forgot exactly what I did. I just followed the manual. I don't recall using a jumper harness.

Good luck.
ya i figure the harness is some gm speacial tool thing. owell i will kepp trying


Okay TPS needs to be connected and u must probe (I taped pins to the DVM probes) thru the wires (+) Blue wire and (-) Blk/Pink wire.
If you get tired of troubleshooting this, you might want to try getting a TPS and ISC from the junkyard and just swapping it out. I think the TPS costs $70 new. I dunno about the ISC.
ya i finially seemed to get the TPS tested and it worked out but I think I am going to replace anyway as the only code i get is E26. When I get a few more dollars ima change the ISC. But I have a feeling my cutoffs might be caused by a failing fuel pump. They are smooth cutoffs at a stop idling in drive and she starts right back up. I've had a few people tell me that they are sure its the fuel pump going. Im not sure, just testing everything now to see if I can find something wrong as the cut offs are intermintint. And gthere are no conditions that are the same. Except that I am always stopped idling in Drive. I just changed the fuel filter in may but b4 i look into the pump and sending unit i think i will change it again along with a neww fuel pump relay. Any suggestions????
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