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Home >> GMC >> 2000 >> C3500 HD 6.5 F, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - Diesel >> Diagnostic Tests >> DTC P0236: Turbocharger Boost System >> Diagnostic Procedures

Diagnostic Procedures

  1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, see ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Check if DTC P1656 is also set. If DTC P1656 is set, diagnose DTC P1656 first. If DTC P1656 is not set, go to next step.
  3. Disconnect vacuum hose from turbocharger wastegate actuator. Install vacuum gauge to vacuum hose. Start and idle engine. Observe vacuum reading. If vacuum is 15 in. Hg or greater, go to next step. If vacuum is not 15 in. Hg or greater, go to step  6.
  4. Disconnect wastegate solenoid harness connector. With engine running, check vacuum gauge reading. If vacuum reading is greater than one in. Hg, go to step  12. If vacuum reading is not greater than one in. Hg, go to next step.
  5. Turn engine off. Connect hand-held vacuum pump to wastegate actuator. Apply vacuum (5 in. Hg) to actuator. If actuator holds vacuum, go to step  7. If actuator does not hold vacuum, go to step  14.
  6. Check all vacuum lines from vacuum pump to wastegate actuator for leaks, deformities or pinches. Repair as necessary. After repairs, go to step  15. If vacuum hoses are okay, go to step  8.
  7. Ensure engine is off. Disconnect vacuum lines to wastegate actuator. Using pliers, grip wastegate actuator rod. Move actuator rod back and forth. If actuator rod moves freely, go to next step. If actuator rod does not move freely, go to step  14.
  8. Check vacuum pump for proper output. Repair as necessary. After repairs, go to step  15. If vacuum pump output is okay, go to next step.
  9. Connect scan tool. Start and idle engine. Observe boost pressure on scan tool display. Increase engine speed to 1500 RPM, and then return to idle. If scan tool displays a change in boost pressure, go to next step. If scan tool does not display a change in boost pressure, go to step  11.
  10. DTC is intermittent. If no additional DTCs are present, see DIAGNOSTIC AIDS . If additional DTCs are present, perform appropriate DTC test.
  11. Replace boost sensor. See BOOST PRESSURE SENSOR  After repairs, go to step  16.
  12. Check for plugged wastegate solenoid filter. Repair as necessary. After repairs, go to step  16. If filter is okay, go to next step.
  13. Replace wastegate solenoid. See WASTEGATE SOLENOID  After repairs, go to step  16.
  14. Replace turbocharger wastegate actuator. After repairs, go to step  16.
  15. Replace vacuum pump. After repairs, go to step  16.
  16. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0236. 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, go to step  2.
  17. Using scan tool, check for DTCs. If any undiagnosed DTCs are set, perform appropriate DTC test. If no DTCs are set, system is okay.
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