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Home >> GMC >> 1997 >> Forward Control 4.3 W, L35, Automatic >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 10 (Engine Controls - Tests W/Codes - 6.5L Diesel (P Series)) >> Diagnostic Trouble Codes >> DTC P1654 - Service Throttle Soon Light Control Circuit >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different variant/trim than selected.
  1. Perform Powertrain ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article. Then go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command light on and off. If light turns on and off, go to next step. If not, go to step 4).
  3. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
  4. Ignition off. Unplug PCM harness connector containing the light control circuit. Turn ignition on, with engine off. If light is on, go to next step. If not, go to step 7).
  5. With fused jumper wire to ground, probe light control driver circuit at PCM connector. If light is on, go to next step. If not, go to step 8).
  6. Check for poor PCM connections. Repair as necessary. After repairs, go to step 10). If connections are okay, go to step 9).
  7. Repair short to ground in SERVICE THROTTLE SOON indicator light control circuit. After repairs, go to step 10).
  8. Check for the following conditions in SERVICE THROTTLE SOON indicator light control circuit:
    • Open ignition feed circuit to bulb.
    • Faulty bulb.
    • Faulty fuse.

    After repairs, go to step 10).

  9. Replace PCM. After replacing PCM, go to next step.
  10. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P1654. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).
  11. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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