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jim
jim, ASE Certified Technician
Category: Jeep
Satisfied Customers: 1317
Experience:  ASE A6,A8,L1 and California Licensed Smog Technician
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2000 JEEP GRAND CHEROKEE: rpms..OIL PRESSURE..PARKED..SAME PROBLEM

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I OWN A 2000 JEEP GRAND CHEROKEE WHEN I START THE TRUCK ALL THE GAUGES COME TO LIFE BUT WITHIN 20 SECONDS ALL THE GAUGES FLATLINE I AM ABLE TO DRIVE THE TRUCK BUT CANNOT TELL THE SPEED ,RPMS ,BATTERY LEVEL, OIL PRESSURE NONE OF THE GAUGES WORK. I AVE DISCONECTED THE BATTERY AND EVERYTHING RESETS AND WORKS AGAIN. ONCE THE VECHILE IS PARKED OVER NIGHT THE SAME PROBLEM OCCURS AGAIN.HELP...........

There several possable causes for this problem here is a list,

Air Bag Control Module (ABCM)
Automatic Zone Control (AZC)
Body Control Module (BCM)
Driver's Door Module
Instrument Panel Cluster (IPC)
Passenger Door Module
Powertrain Control Module (PCM

 

The following diagnostics would need to be preformed to isolate the problem,

Check the Programmable Communications Interface (PCI) bus signals at the Diagnostic Junction Port (DJP) when the gauges are not working.

2. Disconnect the cap from the DJP and scope check each of the lines. They should all have a 7-8 volt uneven square wave.

3. Pin #1 goes to the Powertrain Control Module (PCM) and the Passenger Door Module (PDM).

4. Pin #2 goes to the Driver Door Module (DDM).

5. Pin #3 goes to the Automatic Zone Control (AZC).

6. Pin #6 goes to the Instrument Cluster (IC).

7. Pin #8 goes to the Body Control Module (BCM).

8. Pin #9 goes to the DLC.

9. Pin #5 goes to the Air Bag Control Module (ABCM).

10. If there is no activity on one of the bus lines, check the wire to the module and that module would be bad.

 

You would need a trace scope to check the square wave patterns.

 

Hope this is helpful.

jim and 5 other Jeep Specialists are ready to help you
Customer: replied 7 years ago.
WHERE IS ALL THIS LOCATED DOES IT HAVE TO DO WITH THE COMPUTER ON THE ENGINE FIREWALL OR UNDER THE DASH BEHIND THE FUSE BOX

Here is a picture location of the diagnostic junction port where these test are done from.