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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Mon Mar 02, 2015 7:25 pm Post subject: BUICK - TPS? Crazy |
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Friend's got a 1992 Buick Skylark 3.3L.
Had a TPS code 22 and O2 code, runs rough and occasionally wont start. She replaced the TPS. I got there, cleared the stored faults - car ran great until warmed up then got the rotten egg smell. Replaced the O2 sensor. It sat 20min, tried to fire up and the ECM is in diagnostic mode all by itself with code 22 back.
I checked TPS voltage per my noggin and the book which says measure terminal A (5vref/Gray) and terminal B (signal to ecm/Blue) for below 1.25v closed, 5v open.
What I got was 5v closed, and .5v open. Same on the old sensor.
Stays in diagnostic mode intermittently with the TPS unplugged too. Diag mode spits the codes out and runs the cooling fan.
I know BOP does weird stuff, should this be 5v closed? ECM dead? Or is the pin probing wrong and it should be signal wire to ground? That's what makes sense to me.... _________________ A redline a day keeps the carbon away! |
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chevymad Master B
Joined: 11 Jan 2004 Posts: 5474
1987 Pontiac Formula
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Posted: Mon Mar 02, 2015 7:35 pm Post subject: |
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Code is for tps low voltage. Supposed to set if voltage is lower then .24 volt with throttle closed.
After checking that flow chart has you jumper the 5v to the signal to see if you can set code 21. If it does then wiring/ecm are supposedly ok.
Does sound like your getting backwards readings for some reason. |
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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Mon Mar 02, 2015 7:36 pm Post subject: |
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So the tps dvom readings should be from signal wire to ground, right? Not from the 5vref to the signal?
It's still throwing me for a loop this thing puts itself into diagnostic mode as if there was a paperclip on ALDL A/B _________________ A redline a day keeps the carbon away! |
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chevymad Master B
Joined: 11 Jan 2004 Posts: 5474
1987 Pontiac Formula
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Posted: Mon Mar 02, 2015 7:37 pm Post subject: |
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Wiring diagram also shows that at WOT the signal wire is shorted to the 5v reference. And at idle signal is almost shorted to sensor ground. |
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chevymad Master B
Joined: 11 Jan 2004 Posts: 5474
1987 Pontiac Formula
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Posted: Mon Mar 02, 2015 7:38 pm Post subject: |
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Yes.. you should just be reading the voltage off of the signal wire. Not the delta between it and the reference voltage. |
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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Mon Mar 02, 2015 7:51 pm Post subject: |
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K, then the sensors are good then but still throws a code 22 and stalls out going into it's own diagnostic mode. Hooray for free cars. She should just junk it lol.
ECM to me. _________________ A redline a day keeps the carbon away! |
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chevymad Master B
Joined: 11 Jan 2004 Posts: 5474
1987 Pontiac Formula
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Posted: Mon Mar 02, 2015 7:58 pm Post subject: |
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Did you try the tap test? lol Ya.. I'm getting to where I think that any average car older then obdII should be junked. |
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chevymad Master B
Joined: 11 Jan 2004 Posts: 5474
1987 Pontiac Formula
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Posted: Mon Mar 02, 2015 7:59 pm Post subject: |
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Oh and good luck finding an ecm. I needed one awhile back and had to have it shipped out of cali. Last LG4 ecm available in the napa system at the time. |
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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Wed Mar 04, 2015 7:17 am Post subject: |
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$104 at Oreilly's in the warehouse. _________________ A redline a day keeps the carbon away! |
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chevymad Master B
Joined: 11 Jan 2004 Posts: 5474
1987 Pontiac Formula
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Posted: Wed Mar 04, 2015 7:25 am Post subject: |
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Good! Frankly getting pretty fed up with napa parts. So much so I'm ordering most of my stuff on Amazon now. Paying more for something then replacing it 2 or 3x over the next few months/years is pretty stupid.
Here's hoping the ecm solves the whole issue. |
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aaron_sK Member
Joined: 23 Jan 2006 Posts: 8834 Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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Posted: Wed Mar 04, 2015 8:16 am Post subject: |
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I agree that it is likely the ECM, but I have seen issues on GMs of that era with the TPS wires getting kinked coming out of the weatherpack which then screws up the resistance at the ECM. Might be worth probing the wires at the ECM itself since you're going to have it pulled down anyway. |
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