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1997 GMC K3500 dually 4L80 4x4
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64 Posts
I was having some issues with my 94 Blazer after an injection pump replacement recently. I performed a TDCO with the pump too far advanced and it set a code 88. There is a learning curve with these with Time Set and TDCO and it’s a little confusing at first as I found. I now have a much greater understanding! Anyway, the code 88 set as a hard code and TDCO was -2.02. If I cleared the code with GMTDscan Tech it would come right back with the ignition on, but not running or cranking. Reading previous threads I found one where OkDually said the ECM needed to be replaced at this point which made sense since if you can’t clear the codes, you can’t run another TDCO. I bought an ACDelco reman ECM and was able to get it running great again.

Thanks for the information. Glad you got it running.

Mac
 

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Registered
1997 GMC K3500 dually 4L80 4x4
Joined
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64 Posts
It sure seems like the timing in the IP driven by the stepper motor is what you're fighting. I'm not sure where the arm is for 0 deg. Maybe someone knows and could chime in. Is the arm all the way up? Down? in the middle? I'm asking about the physical position of the arm that the stepper motor moves. For instance, It may be the arm is stuck at 25 Deg advance, even though it's commanded to 0. I think the only way to know is to know where the physical position of the arm is supposed to be at 0 deg. Hope that makes sense.

Mac
 
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