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Home › GMC › 1998 › Envoy › Repair and Diagnosis › Body & Frame › Body, Cab Control Systems › Body Control Module › Diagnosis & Testing › DTC B2618: Courtesy Light Circuit High › Diagnostic Procedures

Diagnostic Procedures

  1. Perform TBC module diagnostic system check. See procedures in TBC MODULE DIAGNOSTIC SYSTEM CHECK  . After performing system check, go to next step.
  2. Turn ignition off. Remove courtesy light relay from BBEC. Turn ignition switch to RUN position. Check voltage between BBEC cavity for courtesy light relay circuit No. 690 (Gray/Black wire) and ground. If battery voltage is present, go to step 7). If battery voltage is not present, go to next step.
  3. Check resistance between courtesy light relay terminals No. 1 and 5. If continuity is present, go to step 11). If continuity is not present, go to next step.
  4. Check resistance between courtesy light relay terminals No. 1 and 2. If resistance is 95 ohms or less, go to next step. If resistance is not 95 ohms or less, go to step 11).
  5. Reconnect all components and wiring. Clear DTCs. Turn ignition off for 10 seconds. Turn ignition switch to RUN position. Turn dimmer switch to ON position. Courtesy light relay should turn on. Check if DTC B2618 is set as a current code. If code is current, go to next step. If code is not current, problem is intermittent. See DIAGNOSTIC AIDS.
  6. Turn ignition off. Disconnect Light Blue TBC module harness connector. Remove circuit No. 690 (Gray/Black wire) from harness connector. Reconnect harness connector to TBC module. Turn ignition switch to RUN position. Check voltage between ground and harness connector circuit No. 690. If battery voltage is present, go to step 10). If battery voltage is not present, go to step 8).
  7. Turn ignition off. Disconnect Light Blue TBC module harness connector. Remove circuit No. 690 (Gray/Black wire) from harness connector. Reconnect harness connector to TBC module. Turn ignition switch to RUN position. Check voltage between ground and harness connector circuit No. 690. If battery voltage is present, go to step 10). If battery voltage is not present, go to next step.
  8. Reconnect all components and wiring. Clear DTCs. turn ignition off for 10 seconds. Turn ignition switch to RUN position. Check if DTC B2618 is set as a current code. If code is current, go to next step. If code is not current, problem is intermittent. See DIAGNOSTIC AIDS.
  9. Replace TBC module. Program TBC and perform relearn procedure. See procedures in TBC MODULE PROGRAMMING/RPO CONFIGURATION  and TBC/BCM RELEARN PROCEDURE  . After programming module, go to step 12).
  10. Repair short to battery voltage in Gray/Black wire. After repairs, go to step 12).
  11. Replace courtesy light relay. After replacing relay, go to next step.
  12. Clear DTCs. After clearing DTCs, perform TBC module diagnostic system check. See TBC MODULE DIAGNOSTIC SYSTEM CHECK  .
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