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Old 07-08-2019, 01:00 PM
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PCM possibly dieing

So the past two weeks when I get into my 2007 Jeep it loses the signal with the key and won't start, no clicks, just will not start. I thought it was the battery in the key fob replaced it, Jeep ran fine for 4 or 5 days and then go to leave and nothing. All the lights on the dash come on and key will lock and unlock doors. I checked the battery it's charged. I get two error codes one is about a PCM error and the other is about losing communication with the key. I have found that after sitting over night it will start the next day and run fine for a couple of days.

Should I go ahead and get a refurbed PCM and replace? I use this jeep as my rainy day jeep, I don't have a lot of money in it but don't want to just start replacing parts.

https://www.wranglerforum.com/f202/h...t-2228306.html

I found this post and it is my exact problem, should I replace the Valve body plate before the PCM?

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Old 07-08-2019, 03:17 PM   #2
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What were the exact codes? I wouldn't go replacing a bunch of parts until you have a good diagnosis done. PCM is a big expense and there are many other issues that can cause communication errors.

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Old 07-09-2019, 06:32 AM
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These are the error codes:
U1001 can bus error
U0151 can bus error
B2100 lost communication with the key
B1644 this had something to do with the rear brake light

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Originally Posted by sequel View Post
What were the exact codes? I wouldn't go replacing a bunch of parts until you have a good diagnosis done. PCM is a big expense and there are many other issues that can cause communication errors.
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Old 07-09-2019, 07:42 AM   #4
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I would not replace the PCM at this time. Not to say that it's not the problem but I wouldn't feel confident that it would solve the problem as no diagnosing has occurred.

I looked up the codes in the manual I have for a 2007. Not factory but close to. I could only find the following codes:

U0151- Lost communication with Occupant Restraint Controller
B1644 - Rear Left Turn Lamp Control Circuit High

Neither of them scream for PCM replacement. The second is likely a short to power. The first could be ORC controller or wiring.

Not sure about the other 2 codes. They don't show in the Chilton's manual i have access to and it follows really close to the factory. Kind of curious if you wrote those down wrong or what scanner you used for pulling codes. Quick search on the net found that B2100 in other jeeps was related to ignition switch circuit.

Hate to say, you might want a pro to diagnose, then fix from there.
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Old 07-09-2019, 08:36 AM
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Thank, I really appreciate all your effort and I will hold off on the PCM right now.

b2100 I was able to find Drivers Door Key Cylinder Switch failure.
U1001 Lost communication with the Can Bus

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Originally Posted by sequel View Post
I would not replace the PCM at this time. Not to say that it's not the problem but I wouldn't feel confident that it would solve the problem as no diagnosing has occurred.

I looked up the codes in the manual I have for a 2007. Not factory but close to. I could only find the following codes:

U0151- Lost communication with Occupant Restraint Controller
B1644 - Rear Left Turn Lamp Control Circuit High

Neither of them scream for PCM replacement. The second is likely a short to power. The first could be ORC controller or wiring.

Not sure about the other 2 codes. They don't show in the Chilton's manual i have access to and it follows really close to the factory. Kind of curious if you wrote those down wrong or what scanner you used for pulling codes. Quick search on the net found that B2100 in other jeeps was related to ignition switch circuit.

Hate to say, you might want a pro to diagnose, then fix from there.
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Old 07-09-2019, 09:41 AM   #6
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Where did you find those code descriptions...what source?

Also what scanner did you use to pull the codes?
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Old 07-09-2019, 01:42 PM
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Quote:
Originally Posted by sequel View Post
Where did you find those code descriptions...what source?

Also what scanner did you use to pull the codes?
The J Scan App

https://www.autoblog.com/2016/12/20/...er-switch-fai/
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Old 07-13-2019, 08:55 AM   #8
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there is nothig like " Lost communication with the Can Bus"

CanBus is a kind of network. It does not communicate. It provides the communication. You have to understand it as kind of wire or pipeline the data flows thru.


Generally loss of comm is hard to diagnose with aftermarket scanners. The best to go is OEM WiTech or (for 2007JK) the older Starscan.


There are several CAN networks in JK.



Powertrain CAN - for engine management and all the important powertrain data

Interior CAN - for body, radio, HVAC, restraints .....
Diagnostic CAN - for diag purposes
plus there is also a one wire LIN bus network - for switches, turn signals, wipers



Not all control units are connected to all networks. In JK only the TIPM and ORC are connected to both powertrain and interior CAN. Where TIPM acts as a gateway between all network nodes.

Actually the B2100 is for Ignition Run/Start Input Circuit Performance
If the TIPM detects that the CAN bus message and the hardwired ignition circuit do not match, it will set this error.


To understand - your ignition switch is not a simple on/off wired directly to some 12volt. It is a double safety . So there is one wire which shows 12V with ignition on and it goes only to TIPM. There is also another wire fed with 5 volts and variable MUX output. This goes from ign switch to the SKIM module.
Monitoring the voltage drop, the SKIM module sees the key position (lock, acc, ign, start) and populates this info on the CAN bus. The TIPM listens to that info and turns the other modules and drivers accordingly.


So long story short - if you turn your key to start positin (to crank the engine) you do not connect any wire to starter or relay.
The only thing what happens is, that ign switch sends a message (voltage drop) to SKIM. SKIM determines what the message is, send a data word thru Can bus network to TIPM. TIPM asks the PCM (and possibly other control units) if the start conditions (sensors, park neutral switch, VIN, voltage and dozen other things) are met. If yes, then the TIPM switches on the starter relay


Besides that it also checks for a valid key and matching VIN. But that is another story





So i would start with an OEM diagnostic tool to look for loss of comm errors.
Then i would check the wiring under steering wheel shroud. Was the clockspring allready replaced? Then i would remove both airbag fuses (teh onesin TIPM within yellow snap.
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Old 07-16-2019, 08:18 AM
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Thank you I will try those.

Quote:
Originally Posted by skjeep1 View Post
there is nothig like " Lost communication with the Can Bus"

CanBus is a kind of network. It does not communicate. It provides the communication. You have to understand it as kind of wire or pipeline the data flows thru.


Generally loss of comm is hard to diagnose with aftermarket scanners. The best to go is OEM WiTech or (for 2007JK) the older Starscan.


There are several CAN networks in JK.



Powertrain CAN - for engine management and all the important powertrain data

Interior CAN - for body, radio, HVAC, restraints .....
Diagnostic CAN - for diag purposes
plus there is also a one wire LIN bus network - for switches, turn signals, wipers



Not all control units are connected to all networks. In JK only the TIPM and ORC are connected to both powertrain and interior CAN. Where TIPM acts as a gateway between all network nodes.

Actually the B2100 is for Ignition Run/Start Input Circuit Performance
If the TIPM detects that the CAN bus message and the hardwired ignition circuit do not match, it will set this error.


To understand - your ignition switch is not a simple on/off wired directly to some 12volt. It is a double safety . So there is one wire which shows 12V with ignition on and it goes only to TIPM. There is also another wire fed with 5 volts and variable MUX output. This goes from ign switch to the SKIM module.
Monitoring the voltage drop, the SKIM module sees the key position (lock, acc, ign, start) and populates this info on the CAN bus. The TIPM listens to that info and turns the other modules and drivers accordingly.


So long story short - if you turn your key to start positin (to crank the engine) you do not connect any wire to starter or relay.
The only thing what happens is, that ign switch sends a message (voltage drop) to SKIM. SKIM determines what the message is, send a data word thru Can bus network to TIPM. TIPM asks the PCM (and possibly other control units) if the start conditions (sensors, park neutral switch, VIN, voltage and dozen other things) are met. If yes, then the TIPM switches on the starter relay


Besides that it also checks for a valid key and matching VIN. But that is another story





So i would start with an OEM diagnostic tool to look for loss of comm errors.
Then i would check the wiring under steering wheel shroud. Was the clockspring allready replaced? Then i would remove both airbag fuses (teh onesin TIPM within yellow snap.

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