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Swapped PCM to try and troubleshoot an issue and now....

8K views 115 replies 10 participants last post by  Redtruck-VA 
#1 ·
Apologies if this is posted in the wrong forum.

I did the 2004 to 2005 PCM swap with a PCM purchased online and flashed with my VIN and mileage. Got with Keith (Charged392) and we have been working on a custom tune.

I'm having an intermittent off idle surge problem that Keith has been trying to help me with. I am running Superchips (for trans tuning) and a custom Diablo tune and Keith suggested it might have something to do with them being stacked. Rather than remove the tunes and start from scratch I thought I could simply swap PCMs to an un-tuned one. I had gotten another 2005 PCM from the local salvage yard and I figured I could use this as a chance to try it out.

Installed the PCM, truck started right up and of course since the VIN didn't match it set codes for the ABS and airbags. Found the off idle surge was still there but significantly less than with the tunes. Swapped PCMs back in for my tuned one and cleared the codes. The surge problem still exists but in addition my ABS seems to have lost its mind.

I get ABS codes Code 82: Number of tone ring teeth out of range and 83: Tire revolution per mile out of range.

I swapped PCMs again to my original 2004 PCM hoping it would somehow reset things. I was able to get code 83 to go away but 82 remains on either my original PCM or the tuned 2005 PCM.

As for the original surging issue I was looking at the logs and noticed that upon acceleration the Throttle Position (apps sensor readings) seem to jump all over the place while my foot is in the same spot. I was able to watch this on my scanner as well. Swapped APPS modules and it still does it. It only jumps around on light throttle, anything more than about 1/4 and it seems to be normal.

I have a Matco Determinator scanner with the appropriate Chrysler cartridge but it doesn't seem to be able set ABS options.

Any ideas how I would be able to get this fixed without having to go to the dealer?

Does anyone know of someone with a Star tool in the Orlando/Daytona area that might be willing to assist?

Truck is a 2004 1500, 5.7, AWD. True Dual exhaust, 2004 to 2005 PCM swap, K&N drop in filter. No other mods.
 
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#6 ·
Given that it did it with the other un-tuned PCM I think there is something else going on. It might be exacerbated by the tune having the pedal adjusted with the extra 10%.

My concern now is if I have to take it to the dealer to get them to reinitialize the ABS I need to put it back to stock. I dont know if just putting the 2004 PCM back in, get them to update the ABS and put the 2005 PCM back in will work. I think so since the VIN adjusted 2005 PCM worked fine. Our local stealership is over $135 an hour and they screwed up a few things when I took it in for the first airbag recall.

I'm really hoping someone here knows of a person around my area who might be able to help. I don't mind paying a reasonable fee, but I can't afford to get other stuff screwed up in the process.
 
#11 ·
I'm wondering if there isn't a ABS sensor going bad....
 
#12 ·
I had been doing some reading online and found where someone else had a similar problem and their Superchips actually resolved it. I reverted the diablo tune back to stock and used the Superchips tuner to do a tire size change. The first time I tried it came back with an error about the ABS module not being found. I turned the key off and back on, the second time it worked and turned off the blinking ABS light. Changed the tire size back to stock, ABS light still out.

Drove it around a little and the surge/hesitation is still there. Reinstalled the custom tune and the ABS light is still out. Checked for codes and there are none.

Evidently there is a difference between how Superchips and Diablo do tire size adjustments. At least I am back where I started.

Now to try and figure out why it's hesitating/surging. I tried cleaning all of the ground connections under the hood but that didn't help. Verified 5V signal at the APPS sensor. Tried three different APPS sensors and it has the issue with each. Checked for vacuum leaks and found none.

Time to dig into the wiring harness..
 
#14 ·
It's an engine hesitation with an occassional miss & stall. Watching the replay of the data logging it looks like the APPS signal changes all over the place at slight pedal pressure. This in turn makes the throttle body % open bounce around.

It doesn't do it at all when in Open Loop (cold), seems to get worse as the engine warms up. I have tried three different APPS sensors, checked all the wiring and cannot find anything wrong.

No codes, not even a pending code after it misses several times in a row.

Attached is an excerpt of one of the data logs showing the pedal position and throttle body positions changing. I don't believe I am moving the pedal when it starts doing this. In fact, I try to keep it steady and keep it acting up in hope it will actually set a code.

I would appreciate any suggestions.
 

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