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2004 gmc envoy_slt
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26 Posts
Discussion Starter · #1 ·
Been having and intermittent pegged oil pressure indication it slowly increases to max then stays there i have replaced the switch/ transmitter but still does it once and a while possible stepper motor ? has anyone ever changed one and what are the steps / oem p/n's of the motor ? . Have found a way to reset the indication i go through several starts and when the gauges do a full sweep towards 0 and the oil pressure sweeps towards a lower indication i abort the start before the gauge goes back to pegged and do this several times till the indication is normal again as if the ecm has to re learn the indication . Does the dealer have an ecm update to address this issue ?
 

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2004 gmc
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Never heard of this being a PCM issue with an update. The I6 engine doesn't have an analog pressure sensor. You could have saved your money replacing it if you'd searched here first. Sorry.

It's only a on/off switch, set for about 18 PSI. What shows up on the gauge is a fictional number calculated by the PCM to FOOL the user into thinking there's a real sensor. Evil GM. The V8 has a real sensor.

So the display will vary a little bit according to RPM, but the problem you have is almost certainly the gauge stepper motor. Run a search - there's a Ebay vendor of replacements and they're very cheap. If you have a way to swap gauge clusters with another trailvoy owner you might confirm the diagnosis. But I bet it's just the stepper.

Trivia question - how steep an offroad hillclimb does it require to get the pressure switch to click off and tell you you're about to blow your engine? 45 degrees. :D
 

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2004 gmc envoy_slt
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26 Posts
Discussion Starter · #4 ·
I know it was just a switch and got for free under warenty from the used car dealer i bought it from . it was the ezier place to start next will give the stepper motor a blast of contact cleaned from LPS might fix it ? Works on aircraft lol
 

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The data is "managed", but not truly false. Similar things happen in reverse for the coolant temp, where the display is filtered to make it look like it's really 210 degrees when it's really anything from 180-220. Keeps the driver from worrying.

The raw data stream for engine coolant shows the truth. The PCM can't deal with analog data for oil pressure, but some owners have put in their own sensors running a separate gauge.
 
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