Jeep Grand Cherokee 2.7 CRD 2002 - Non start, no communication with ECU - Fixed #
Posted by Shaun Dale on February 8, 2011, 9:25 pm
Year of Manufacture *: 2002 Engine Size and Code *: 2.7 CRD ( Optional ) Scanner Used: Multiscan
Vehicle trailered in. No comms with engine, further investigation showed no comms with anything. Could get engine/gearbox comms on EOBD but no codes stored (but immo codes wouldn't be anyway). A look at the diagnostic socket wiring diagrams led me to believe that nothing on the PCI bus was talking. Put the 'scope on pin 2 (PCI line)found it was stuck low, some signal but less than 500mV. Out with the multimeter, resistance to earth (battery disconnected)was about 4 Ohms. At this point I find out that where a 2000MY Cherokee has a diagnostic junction port that allows all the devices on the bus to be seperated for testing,it has been deleted by 2002MY . A lengthy investigation followed, disconnecting BCM, Instruments,Climate, radio etc. etc. Traced finally to gear selector module, when it was unplugged the short disappeared.I found that the PCB in the selector has components on the bottom with nothing to physically keep the sliding shield from rubbing it! I removed C11 (a surface mount device about 2mm long), cleaned the solder smear off and refitted it. When everything was re-connected it all worked properly. When rebuilding the gear slector I put in a piece of fibreglass reinforced teflon sheet (don't ask ) as a seperator but any sensible piece of plastic sheet would do. A new gear selector was about £420 with vat so a repair saved the customer quite a bit of money. In retrospect the fact that all doors except the driver's door unlocking on the remote key could be a clue as it seems the driver's door unlock is handled by the PCI bus because it unlocked correctly afterwards. Shaun