Central timer module

NOTE: The following tests may not prove conclusive in the diagnosis of the high-line version of the Central Timer Module (CTM). The most reliable, efficient, and accurate means to diagnose the high-line CTM requires the use of a DRBIIIT scan tool and the proper Diagnostic Procedures manual.

If the problem being diagnosed involves only the RKE horn chirp feature, see Relays in the Diagnosis and Testing section of this group to test the horn relay before testing the CTM. If the relay checks OK; or if the problem being diagnosed involves the rolling door locks, door lock inhibit, central locking or enhanced accident response features, further diagnosis of the CTM should be performed using a DRBIIIt scan tool as described in the proper Diagnostic Procedures manual. If the problem being diagnosed involves only the RKE driver unlock feature, be certain that the feature is enabled using a DRBIIIt scan tool and the proper Diagnostic Procedures manual.

Also, if the problem being diagnosed involves only the driver side front door, see Relays in the Diagnosis and Testing section of this group to test the driver unlock relay before testing the CTM. For circuit descriptions and diagrams, refer to 8W-61 - Power Door Locks in Group 8W - Wiring Diagrams.

(1) Check the fuses in the junction block. If OK, go to Step 2. If not OK, repair the shorted circuit or component as required and replace the faulty fuse.

(2) Check for battery voltage at the fuse in the junction block. If OK, go to Step 3. If not OK, repair the open circuit to the Power Distribution Center (PDC) as required.

(3) Disconnect and isolate the battery negative cable. Remove the Central Timer Module (CTM) from its mounting bracket to access the CTM wire harness connectors. Refer to Central Timer Module in the Removal and Installation section of Group 8E - Instrument Panel Systems for the procedures.

(4) Unplug the wire harness connectors from the CTM. Check the wire harness connectors and the receptacles in the CTM for loose, corroded, or damaged terminals and pins. If OK, go to Step 5. If not OK, repair as required.

(5) Probe the ground circuit cavity of the 14-way CTM wire harness connector and check for continuity to a good ground. Repeat the check between the ground circuit cavity of the 18-way CTM wire harness connector and a good ground. In each case, there should be continuity. If OK, go to Step 6. If not OK, repair the open circuit(s) to ground as required.

(6) Connect the battery negative cable. Check for battery voltage at the fused B(+) circuit cavity of the 14-way CTM wire harness connector. If OK, go to Step 7. If not OK, repair the open circuit to the junction block as required.

(7) Probe the door lock switch output (lock) circuit cavity of the 18-way CTM wire harness connector and check for battery voltage as you actuate each power lock switch to the Lock position. If OK, go to Step 8. If not OK, repair the open circuit from either or both power lock switch(es) to the CTM as required.

(8) Probe the door lock switch output (unlock) circuit cavity of the 18-way CTM wire harness connector and check for battery voltage as you actuate each power lock switch to the Unlock position. If OK, go to Step 9. If not OK, repair the open circuit from either or both power lock switch(es) to the CTM as required.

(9) Disconnect and isolate the battery negative cable. Reinstall the wire harness connectors to the CTM. Connect the battery negative cable. Back-probe the door lock driver circuit cavity of the 18-way CTM wire harness connector and check for battery voltage as either power lock switch is moved to the Lock position. Repeat the test pressing the Lock button of the Remote Keyless Entry (RKE) transmitter. If OK, go to Step 10. If not OK using the power lock switch, but OK with the RKE transmitter, see Power Lock Switch in the Diagnosis and Testing section of this group. If not OK using the RKE transmitter, but OK  with the power lock switch, see Remote Keyless Entry Transmitter in the Diagnosis and Testing section of this group. If not OK, with the power lock switch or the RKE transmitter, replace the faulty CTM.

(10) Back-probe the door unlock driver circuit cavity of the 18-way CTM wire harness connector and check for battery voltage as the power lock switch is moved to the Unlock position. Repeat the test pressing the Unlock button of the RKE transmitter twice within five seconds. If OK, see Power Lock Motor in the Diagnosis and Testing section of this group. If not OK using the power lock switch, but OK with the RKE transmitter, see Power Lock Switch in the Diagnosis and Testing section of this group. If not OK using the RKE transmitter, but OK with the power lock switch, see Remote Keyless Entry Transmitter in the Diagnosis and Testing section of this group. If not OK, with the power lock switch or the RKE transmitter, replace the faulty CTM.