For all of the most common wiring issues listed here below and any others you may find where a harness has rubbed through, verify that the motor mounts are in good condition. Chrysler harness routing causes many problems all on its own, but many faults only show up after motor mounts failure. Evertime the engine shifts, it stresses and rubs thru the engine harness in many places. You may find and repair the wiring damages, but if you dont repair the root cause, other wiring problems may develop later down the road.
Harness Faults found at AC compressor;
On many applications, a sub-harness is routed close to the compressor or a hard AC line. The harness can rub through on these AC components causing shorts to ground , or just rub some insulation off and cause shorts between wires inside the harness. Depending on what wires are on that harness and which ones rub through can cause any number of codes and symptoms. This issue is NOT specific to any "favorite" model or engine, it happens on ALL Chrysler applications.
Harness Faults over Transmission or Transaxles:
Chrysler lays many of the engine harnesses over the transmission or transaxle, and if they are loose the tend to rub through. The chafing can occur on the transmission body casting on all applications, transmission mounts on (minivans), or over the solenoid packs (minivans).
Harness Faults Over 4.0L Head Bolts:
The 4.0L I6 engines have a very common harness chaffing issue over the left rear head bolt. This causes coil primary codes, O2 sensor codes, TPS codes, and ASD realy codes, stalling, misfiring, and a number of ther symptoms related to the components and sensors routed through that harness. SO, if you have a 4.0L truck or SUV with drivability faults or a list of stored codes check your engine harness at the back of the valve cover.
Battery Acid Damage:
On many applications Chrysler routes a harness under the battery tray. If the battery has ever leaked the harness protection covers traps the leaking acid and it eats through the insulation. This causes many codes and symptoms, so check for evidence of battery leaking and check wiring harness underneath the tray.
On many later JTEC and SBEC modules, Chrysler may have just ran out of PCM grounds to run all of the different actuators.
SO, their solution was to Ground some circuits directly onto the PCM casing and pray and hope that those PCM mounting bolts or screws make a good connection. But as these vehicles aged, many bolts and screws get corroded causing all kinds of stalling and drivability complaints.
Just keep in mind when diagnosing a late model JTEC or SBEC application the fastest way to check for ground problems is to run a jumper wire between the PCM case and the battery ground and see if the symptoms dissapear?
