Pontiac Problems? Ask a Mechanic for Answers ASAP
My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.
With the tach issue and check engine light flashing and you have replaced the crank sensor and checked over all engine wiring and connections and found no issues at all this sounds like the PCM itself is at fault.I have seen this fail before internally needing replaced for this issue here.I would have the PCM power and grounds tested to make sure they are all o.k. and no wiring damaged leading to the PCM and make sure the battery cables are clean and tight at the battery as well as to where the cables run and connect to.If these are all found to be o.k. the PCM usually needs replaced to correct this here.If any other gauges or electronics are acting up with this issue here the other component I see that causes this is the electronic ignition switch itself needing replaced.
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The pcm can be purchased used or new and from a dealer or local parts store or salvage yard.Wherever it is ordered or obtained from though it will need programmed by a dealer to match your model vehicle here.
The ignition switch can be tested by having the signals tested from the switch to see if it is sending the correct signals.This will need done using a scan tool to observe the signals from the switch and a multi meter for testing.
If you have no other electrical issues with your model here though except what is occuring here I would lean more on the PCM itself at fault needing replaced.I have had to replace this before for this type of fault here.
Let me know if you need anything else and feel free to rate my help here.
The PCM or sometimes called the ECM are the same thing.This would be either the powertrain control module or engine control module.
The PCM is located inside the air filter box in the engine bay.You would need to take apart the air filter box to access it.Below is a picture of it.
I apologize for the delay.
Was the PCM programmed when it was installed?
This is a tough one for me myself to answer here but someone else may be able to help further on this.
I will open your question up for others here to see if someone else can assist further on this as there may be others here that may have more info on what to check or do with this issue.I hope you can get this resolved with ease.No need to reply to my last post here unless it is a last resort as it will keep your question locked to me and others will not be able to view it.If you feel you want to continue to work with me on this feel free to reply at any time but keep in mind in some cases it can be difficult to fully diagnose or help repair this without seeing your vehicle.