CAN BUS Troubles - Jeep JK fitted with Hemi engine

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ronw38
TwoWaves
TwoWaves
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Joined: Sun Aug 27, 2017 8:00 am

Re: CAN BUS Troubles - Jeep JK fitted with Hemi engine

Post by ronw38 »

Kona and Liviu are on the money. Try this, don't take any measurements or make connections from the OBD2 plug, scope can at the most accessible module [usually ABS]scope at 500ms division plus/minus 10v free running no trigger get familiar with looking at a good normal pattern when vehicle is OK- idle voltage 2.5v Hi 3.5v Lo 1.5v spikes and noise are normal pause and zoom just to observe general packet patterns don't look at bits or try decoding at this stage once you know what a good pattern looks like take captures when the system faults you should see a change in voltage levels pulled up/down and or pattern distortion, time to un plug and re plug modules one by one to see if a good pattern returns any with a terminating resistor may cause extra distortion but should return the pattern if faulty? wiring/connectors may be shorted to ground/power, if the signals disappear raise above battery voltage to 20v. As the lads have said you cant scope at the OBD plug when the signals go through a gateway to the plug early systems and some makes went directly to the plug hence the confusion. Cheers Ron

French Chris
OneWave
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Joined: Mon Jan 25, 2021 10:14 am

Re: CAN BUS Troubles - Jeep JK fitted with Hemi engine

Post by French Chris »

OK Thanks for your help guys,

I will try that.

French Chris
OneWave
OneWave
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Joined: Mon Jan 25, 2021 10:14 am

Re: CAN BUS Troubles - Jeep JK fitted with Hemi engine

Post by French Chris »

Thanks for your advice Ron.

Mekanic
Newbie
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Joined: Mon Aug 21, 2023 2:56 pm

Re: CAN BUS Troubles - Jeep JK fitted with Hemi engine

Post by Mekanic »

I have a 2007 Wrangler with 6.0 Liter VORTEC LS1 Gen3. What are the DTC's your seeing from the "scanner"?
I didn't see a solution, or did I miss it in the posts?

French Chris
OneWave
OneWave
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Joined: Mon Jan 25, 2021 10:14 am

Re: CAN BUS Troubles - Jeep JK fitted with Hemi engine

Post by French Chris »

Hi Mekanic,

I remember reading posts on Jeep Owners Club few years ago about someone carrying out a LS1 conversion in a Jeep wrangler JK. Was it you?

I sorted out my CAN Bus issue in the Summer 2021 by buying a second hand wire harness from USA and modifying it to fit the RHD engine bay as the ABS and battery are at opposite side. The old harness going to the ABS module was the culprit.

If you have CAN Bus issues with yours being a 2007 it is very likely to come from the old wire harness from the engine bay.

Mekanic
Newbie
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Joined: Mon Aug 21, 2023 2:56 pm

Re: CAN BUS Troubles - Jeep JK fitted with Hemi engine

Post by Mekanic »

Probably was me...
The initial "guy" draped an after market, stand-alone harness over the existing JEEP harness and got it running...basically "Hot-Wired".

I "combined" the two harnesses into one...stripping out all the unnecessary Jeep engine, Alternator, Fan and Transmission stuff. Stripped most of the "PCM" terminals but left the CAN Busses and LIN Bus and kept the Cluster and Body Control (CCN Node). Left the TIPM "intact"..but still slightly problematic. I didn't pull the ABS, AirBag , HVAC, Console and Horn.

HVAC is "operationally hacked" to ground PCM-3 Pin#11 to get the Compressor Coil and fan combined...But now getting intermittent "No Starts" when engine is shutdown after short trips. Still struggling with this at the moment...and it appears to be CAN Bus related.

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