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Discussion Starter #1
1993 Seville 4.9L SLS with 82000 miles :
I usually run a diagnostic with the OBD every 3-4 weeks. Today I recieved a code. "Code PO70 History".
Looking in my Chilton manual, (I know its not the best manual), I find that it has to do with the Throttle positioning sensor.
Now here come the questions:
Didnt notice any drivability problems and still dont. Other than the last week or so my milage went to total crap. I guess the TP sensor could explain that ?
Would it be a history code because, (From the manuall), "A DTC is set" so now the PCM is using "An artificial flow for throttle position". Basicly meaning Its compensated so the code is shown as a history ?
To check the sensor the manual refers to 2 terminals, A & B. How do I know which is A and which is B ?
And the last questions for now. What does this thing look like ? Does anyone have a Pic ? The only Pic this manuall has is for a 4.6 and it doesnt look like anything under my hood.

I believe I know where my TP sensor is ! But just in case ! The main question is for the A & B terminals.
Hopefully someone here can help me out, and let me know what courses of action I need to persue..
Thanx in advance !!

:worship:
 

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Re: OBD

TPS check:
1. Check the voltage from ECM to TPS - disconnect the TPS harness connector andinstall the probes of a voltmeter on the "ref" terminal (+) gray wire and the "grnd" terminal (-) black/black-pink wire. In ignition on (not running) it should read approx. 5volts. If not available, then its an open circuit from ECM or bad ECM.
2. Probe the "sig" terminal (+) dark blue wire and "grnd" (-) terminal on TPS sensor. Check voltage with throttle fully closed, then gradually open the throttle to full. There must be 0.44...0.55 volts with closed throttle and 4...4.5 volts with throttle full open. And voltage should increase smoothly. If those readings are incorrect, then TPS needs replaced


Maybe it helps you a little...
 

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Discussion Starter #3 (Edited)
Yes that does help me. A little simpler and easier to understand.
Hopefully will have time to check it today and see what I get.
One more thing. Is step 2 also done with ignition on/engine NOT running ?
Thankyou very much!
 

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Re: OBD

Murphyg said:
Yes that does help me. A little simpler and easier to understand.
Hopefully will have time to check it today and see what I get.
One more thing. Is step 2 also done with ignition on/engine NOT running ?
Thankyou very much!
About this step two - yes, ignition on.
TPS is just variable resistance potentiometer...maybe it need only cleaning
 

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Discussion Starter #5
Thought I'd Update

I'm not to sure but everything seems to be allright now ?
While waiting to get my voltage tester back from my neighbor (Which I still havent) I located the TPS, checked the connectors, made sure averything was clean then put it "all" back together.
Forgot to reconect the TPS, started the car, (knew right away what I didnt do), got check engine then of course another code.
Reconnected everything, started and idled the car twice, cleared all codes, then reset the computer.
It's been a week less a day now and I havent gotten anymore codes. No history, nothing. And my mileage appears to be back to normal.
Im a bit confused though. Eveything appears to be ok; but seeing as I wasnt able to test anything and I didnt make any adjustments other than resetting what does that mean ?
Was that original PO70 code a fluke ? Some kind of surge or something ? Should I just assume that everything is fine (For now) ? :confused:
:histeric:
 
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