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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 87 (Engine Controls - Self-Diagnostics - 6.6L Diesel) >> Diagnostic Tests >> DTC P0236: TC Boost System (Ca) >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Start the engine. Allow the engine to reach operating temperature. Turn OFF the ignition. Turn ON the ignition, with the engine OFF. Observe the BARO sensor and the boost sensor using the scan tool. Compare the BARO sensor pressure to the boost sensor pressure. Is the BARO sensor pressure more than the boost sensor pressure by a margin of 10 kPa or more? If yes, go to step  9. If no, go to next step.
  3. Turn OFF the ignition. Remove the boost sensor from the intake manifold. Inspect for the following conditions:
    • A plugged sensor port.
    • A damaged hose.
    • A restricted hose.
    • A disconnected hose.

    Did you find and correct the condition? If yes, go to step  18. If no, go to next step.

  4. Turn ON the ignition, with the engine OFF. Connect a hand vacuum pump to the sensor port. Observe the boost sensor pressure on the scan tool as you SLOWLY apply vacuum 1 in. Hg at a time up to 15 in. Hg. Each inch of vacuum should result in a 3-4 kPa drop in pressure. Does the scan tool indicate the boost sensor is operating normally? If yes, go to next step. If no, go to step  9.
  5. Disconnect the hand vacuum pump from the sensor. Does the scan tool indicate that the boost sensor pressure returns to the value observed in step  2? If yes, go to next step. If no, go to step  16.
  6. Inspect for the following conditions:
    • EGR throttle valve that is stuck closed.
    • Restriction in the air cleaner or the intake tube.
    • Leaking charged air cooler.
    • Leaking charged air pipes and connecting clamps and hoses.
    • Leaking intake manifold.

    Did you find and correct the condition? If yes, go to step  18. If no, go to next step.

    7. CAUTION: Wear safety glasses when using compressed air in order to prevent eye injury.
  7. Turn OFF the ignition. Remove the hose from the wastegate actuator tube. Apply compressed air, not exceeding 45 psi, to the actuator tube to open the wastegate. The wastegate should begin to open near 30 psi and be fully open at 45 psi. The actuator rod stroke should measure near 4 mm. Remove the compressed air from the actuator tube. Does the wastegate move to the fully extended position and return to the fully retracted position? If yes, go to next step. If no, go to step  15.
  8. Remove the air intake pipe. Inspect for any condition that may cause poor turbocharger performance, such as the following:
    • Bent or broken blades.
    • Worn shaft bearings.
    • Oil leaks.

    Did you find a problem with the turbocharger? If yes, go to step  15. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.

  9. Disconnect the boost sensor electrical connector. Connect a test lamp to a good ground. Probe the 5-volt reference circuit of the boost sensor with the test lamp. Does the test lamp illuminate? If yes, go to next step. If no, go to step  11.
  10. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the boost sensor and the signal circuit of the boost sensor. Does the scan tool indicate that the pressure is more than 254 kPa? If yes, go to step  13. If no, go to step  12.
  11. Test the 5-volt reference circuit of the boost sensor for high resistance or an open. Did you find and correct the conditions? If yes, go to step  18. If no, go to step  14.
  12. Test the signal circuit of the boost sensor for an open. Did you find and correct the condition? If yes, go to step  18. If no, go to step  14.
  13. Inspect for poor connections at the boost sensor. Did you find and correct the condition? If yes, go to step  18. If no, go to step  16.
  14. Inspect for poor connections at the ECM. Did you find and correct the condition? If yes, go to step  18. If no, go to step  17.
  15. Replace the turbocharger. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  18.
  16. Replace the boost sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  18.
  17. Replace the ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram ECM. See ENGINE CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  18. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  19. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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