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Is my PCM fried?

Gabes06

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Dec 24, 2021
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North Carolina
So, I recently had a electric fan installed on my 06 TJ when I was out of town. the guy who did it installed a new temperature probe in my thermostat housing to hook a wire to so that it could control when my fan cycles on and off. no problems with that, but it left my factory wiring plug dangling and was giving me a code, I was poking around trying to see how I could get them both to work together so I wouldn't have to have a engine code up all of the time. It was late and I was tired (should have just went to bed so id be rested and not apt to do incredibly dumb stuff like accidently put my ground clip to the positive on my battery) while doing this I inadvertently put 12 volts into the ground pin on the plug and now all of the sensors in my engine (MAP, throttle position, intake air, ambient air) are all sending low voltage codes, and my engine will crank but not turn over.

these are the steps I've taken so far to try and diagnose;
-gone through my PCM plugs and checked all the wires in the harness for function, all worked.
-disconnected the battery and let it sit to try and reset the PCM (4hrs)
-I've reset the PCM
-I've taken the PCM out of the vehicle and opened it to inspect the PCB traces and various components for damage (everything LOOKED normal and undamaged)
-check all fuses in glovebox and next to battery
wondering where I should go from here, new sensors? new PCM? I'm not extremely comfortable with my abilities when it comes to computers in the vehicle, but I know enough to make basic diagnoses, any help or suggestions would be appreciated, thanks fellas
 
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Jerry Bransford

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There's a Jeep PCM company expert that is here every so often, they are PCM experts. I'd give Mark a call at www.wranglerfix.com and he can give you solid advice. @Wranglerfix

You checked all of the fuses in the Power Distribution Center behind the battery and in the fuse panel behind the glove box right?
 
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Gabes06

Gabes06

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Dec 24, 2021
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There's a Jeep PCM company expert that is here every so often, they are PCM experts. I'd give Mark a call at www.wranglerfix.com and he can give you solid advice. @Wranglerfix

You checked all of the fuses in the Power Distribution Center behind the battery and in the fuse panel behind the glove box right?
Yep, should have mentioned that as well. thanks ill give him a message after the holidays are over
 

ItchyDong

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May 20, 2020
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Dothan, Alabama
1.) Does your fuel pump prime when you turn the key on? If so, ASD circuit is alive. Go to step 2.
2.) With key on engine off, back probe TPS 5v supply (yellow/pink wire), check for 5 volts. If 5 volts is present go to Step 3.
3.) With key on engine off, unplug TPS connector. Check for 5 volts on the signal wire (brown/orange wire). If 5 volts is present, go to step 4.
4.) With TPS connector still unplugged, connect an incandescent test light to battery positive, touch TPS sensor ground pin (dark blue/dark green wire). Test light should light. If it lights go to step 5.
5.) Run a resistance check through TPS sensor. If it displays OL, you've fried your TPS, and there's a good bet you fried the other sensors you listed considering they all share a ground and you back fed battery voltage without a load. Your

Always use an incandescent test light as a jumper. The bulb will protect you from bone head moves like this. There's a legit chance you fried the PCM. Those grounds all tie in to the PCM in a couple of places. You sending battery voltage to them could easily cook the ASD relay control driver. I have a suspicion you won't make it past step 2. Good luck.
 
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Wranglerfix

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May 2, 2019
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Hollywood, Fl
Good morning gentlemen,

I hope you all had a merry Christmas. Sorry for the delay in responding as I needed to detach and spend a few days fishing.

@Gabes06 it sounds like you fried the pcm and there is no repairing these units. Hard shifts, high transmission temperatures, o2 sensors showing bad when good and 1600 codes are are telltale signs of a faulty pcm.

You can call me to discuss in further detail.

Thanks,

Mark
 
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