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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 P0236 - Turbocharger Boost System >> 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. Check if DTC P1656 is also set. If DTC P1656 is present, diagnose this DTC first. See DTC P1656 test. If DTC P1656 is not present, go to next step.
  3. Disconnect vacuum hose from turbocharger wastegate actuator. Install vacuum gauge to vacuum hose. Start engine. With engine at idle, vacuum reading should be 15 in. Hg. If vacuum reading is equal or greater than 15 in. Hg, go to next step. If vacuum reading is less than 15 in. Hg, go to step 6).
  4. Disconnect wastegate solenoid harness connector. With engine running, check vacuum gauge reading. If vacuum reading is greater than 1 in. Hg, go to step 10). If vacuum reading is less than 1 in. Hg, go to next step.
  5. Turn engine off. Connect a hand-held vacuum pump to wastegate actuator. Apply 5 in. Hg of vacuum to actuator. If actuator holds vacuum, go to step 7). If actuator does not hold vacuum, go to step 12).
  6. Check all vacuum lines from vacuum pump to wastegate actuator for leaks, deformities or pinches. Repair as necessary. After repairs, go to step 13). If vacuum hoses are okay, go to step 9).
  7. Ensure engine is off. Disconnect vacuum lines to wastegate actuator. Using a pair of 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 or does not move freely, go to step 12).
  8. DTC is intermittent. If no additional DTC(s) are present, see DIAGNOSTIC AIDS. If additional DTC(s) are present, diagnose affected DTC(s).
  9. Check vacuum pump for proper output. Repair as necessary. After repairs, go to step 13).
  10. Check for plugged wastegate solenoid filter. Repair or replace as necessary. After repairs, go to step 13). If filter is okay, go to next step.
  11. Replace wastegate solenoid. After replacing solenoid, go to step 13).
  12. Replace turbocharger actuator. After replacing actuator, go to next step.
  13. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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, repeat step 2).
  14. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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