I am testing this Grand Cherokee for no start but how come there is no dash lights when I turned the key on? I tried hooking up the scanner but got no communication from my scanner? After reading previous ATS fixes, the front control module (FCM) is the common fix for this problem and when I replaced that, the dash light came alive but still no start? The Can B bus wires seem to work because my radio is now working. Is this a Can C bus wires failure? It also mentioned from ATS that the wireless ignition node (WIN) is another suspect but how do I test it?
Since you have replaced the FCM, I would try global resetting of the modules by disconnecting the battery cable and joining them together for a few minutes. If this does not work, try these:
1.) The WIN module can be tested by checking its terminal voltage power at pin 1 or light blue red wire which is supplied by the power distribution center. Ground signal to this module is sent at pin 4 or the black light blue wire. If both signals are present then this module is defective. The Can C bus data wires can be tested at pins 5 and 6 which should be equal to the voltage reading at FCM pins 9 and 8 (using the computer data lines wiring diagram).
2.) Do the same power test at the PCM by testing at pin 12 with pink white wire and ground terminals at pin 12, 13 and 14 which are all black wires. Bus wire voltage reading at pin 35 and 34 should be the same also at FMC pins 9 and 8.
Any mismatched or shorted readings above should point you to a defective WIN or PCM module. If you are replacing either the WIN or PCM module, check with the dealer if programming is necessary.
Check this approximate 2008 Jeep Grand Cherokee Power Wirings below. Note the computer data line bus wires shown in blue and gray colors. At KOEO, it should read 2.5 volts across.
You can get the EXACT wiring diagram from most parts stores if you ask for it while buying parts or get it FREE online 24/7 when you join ATS.
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