6th Gen ('00-'05): PCM replacement
Thread Starter
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Joined: Apr 2018
Posts: 5
PCM replacement
I have an 04 Monte Carlo SS (not supercharged) and lately I’ve had rough idle issues which led to stalling. I went and got the codes read and there were a lot of issues that got dealt with but the MAF code wouldn’t go away. I got a new one, got a new wiring harness, still throws the same code. I called my mechanic to come take a look at it and he hooked it up to his computer and the MAF sensor is reading at 0. It’s not getting anything. He rewired it completely and it still is at 0. He says that it’s my PCM and I’m looking into getting one but is that really my only option? And if so, do I need to get it programmed? I have put a bit of money into this car already and I love my car but I am afraid that I will do this and still have issues. Any advice would be helpful.
Joined: Apr 2010
Posts: 12,605
From: Mentor, Ohio
From my experience, most of the time someone jumps to the PCM/ECM, it is because they have not done all the required diagnostics, so they are jumping to a conclusion and hoping for the best. Before going further, if your mechanic has not done so already, he should ensure that the wiring for the MAF is working. Odds are the shop book probably has some diagnostics to follow for this using a volt meter. If all that checks out, I would then ensure there is continuity on all the wires (that there is no break between there end points). Ensure there is no fuse related to the circuits for the MAF.
One issue I dealt with on my O2 sensor was a single pin not making contact in the connector. This was found by using a paper clip to probe the pins, one had a very loose fit.
But, if the PCM is truly bad, yes it will need programmed for your car. It needs the correct programming and VIN programmed to it. You will need to work with a dealership or a shop with the correct equipment.
I can also re-program PCMs. I offer a small service doing this for people, here is my thread about it:
https://montecarloforum.com/forum/pr...-3100-a-42773/
PCMs are inexpensive to get for these cars. I've gotten a couple for tuning for myself from eBay. It does not matter what car they come from, as long as the service numbers match. PCMs for these cars are about $15-$25 shipped from sellers on eBay.
One issue I dealt with on my O2 sensor was a single pin not making contact in the connector. This was found by using a paper clip to probe the pins, one had a very loose fit.
But, if the PCM is truly bad, yes it will need programmed for your car. It needs the correct programming and VIN programmed to it. You will need to work with a dealership or a shop with the correct equipment.
I can also re-program PCMs. I offer a small service doing this for people, here is my thread about it:
https://montecarloforum.com/forum/pr...-3100-a-42773/
PCMs are inexpensive to get for these cars. I've gotten a couple for tuning for myself from eBay. It does not matter what car they come from, as long as the service numbers match. PCMs for these cars are about $15-$25 shipped from sellers on eBay.
Thread Starter
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Joined: Apr 2018
Posts: 5
Thank you! So, he did test the wires and now that he changed them they are getting the correct voltage, no breaks either. I didn’t know that I only needed to match the part number. That is very helpful information! Now I just need to take it apart again and write it down. I’m also going to look into the possibility of a fuse to the MAF. I didn’t think of that. I truly just don’t understand how it could read at 0. I disconnected both battery cables and let it sit for an hour, I heard that would reset the PCM. I’m going to take her for a spin and see how she runs. If I do need a PCM I will definitely be in contact with you about reprogramming it. Thanks again!!
Joined: Apr 2010
Posts: 12,605
From: Mentor, Ohio
The MAF itself could also be bad. If you replaced it, I would recommend using a genuine AC Delco MAF. Too many people have had issues with non-AC Delco MAF sensors.
