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Home >> Chevrolet >> 1997 >> C3500 HD 7.4 J, Automatic >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 3 (Engine Controls - Tests W/Codes - 6.5L) >> Diagnostic Trouble Codes >> DTC P0571 - Cruise Brake Switch 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 - 6.5L DIESEL article. Then go to next step.
  2. Install scan tool. Turn ignition on, with engine off. Apply brakes. If scan tool displays cruise brake switch closed, then open when brakes are released, go to next step. If scan tool does not display cruise brake switch closed then open when brakes are released, go to step 4).
  3. Apply brakes again. If scan tool displays cruise brake switch open, then closed when brakes are released, go to step 8). If scan tool does not display cruise brake switch open, then closed when brakes are released, go to step 6).
  4. Turn ignition off. Disconnect brakelight switch connector. Turn ignition on, with engine off. Using a test light connected to ground, probe normally open feed circuit (terminal "B") of brake light switch connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 9).
  5. Disconnect brakelight switch connector. Connect a jumper wire between normally open feed circuit and normally open signal circuit of brakelight switch connector. If scan tool displays cruise brake switch closed, go to next step. If scan tool does not display cruise brake switch closed, go to step 10).
  6. Disconnect brakelight switch connector. Turn ignition on, with engine off. Using a test light connected to ground, probe normally closed feed circuit of brake light switch connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
  7. Disconnect brakelight switch connector. Connect a jumper wire between normally closed feed circuit and normally closed signal circuit of brakelight switch connector. If scan tool displays cruise brake switch closed, go to step 15). If scan tool does not display cruise brake switch closed, go to step 14).
  8. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
  9. Check for open or short to ground in normally open feed circuit. Repair as necessary. After repairs, go to step 17).
  10. Check for open or short to ground in normally open signal circuit. Repair as necessary. After repairs, go to step 17). If circuit is okay, go to next step.
  11. Check for poor connection at normally open signal terminal of PCM. Repair as necessary. After repairs, go to step 17). If connection is okay, go to step 16).
  12. Check for open or short to ground in normally closed feed circuit. Repair as necessary. After repairs, go to step 17).
  13. Check for open or short to ground in normally closed signal circuit. Repair as necessary. After repairs, go to step 17). If circuit is okay, go to next step.
  14. Check for poor connection at normally closed signal terminal of PCM. Repair as necessary. After repairs, go to step 17). If connection is okay, go to step 16).
  15. Replace brakelight switch. After replacing switch, go to step 17).
  16. Replace PCM. After replacing PCM, go to next step.
  17. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P0571. 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).
  18. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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