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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 51 (Engine Control System - Self-Diagnostics - 4.2L) >> Diagnostic Tests >> DTC P1512: Command Vs. Actual Throttle Position Correlation Error >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. 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. Are DTCs P1120, P1220, P1221, P1271, P1275 and P1280 also set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, go to next step.
  3. Turn OFF the ignition. Inspect the throttle body for the following conditions:
    • A throttle valve that is NOT in the rest position.
    • A throttle valve that is binding open or closed.
    • A throttle valve that is free to move open or closed WITHOUT spring pressure.

    Did you find any of these conditions with the throttle body? If yes, go to step  15 . If no, go to next step.

    4. NOTE: The test lamp may momentarily flash when testing these circuits. This is considered normal.
  4. Disconnect the throttle body harness connector. Turn ON the ignition, with the engine OFF. Probe the TAC motor control 1 and 2 circuits with the test lamp connected to ground. Did the test lamp illuminate and remain illuminated on either circuit? If yes, go to step  8 . If no, go to next step.
    5. NOTE: The test lamp may momentarily flash when testing these circuits. This is considered normal.
  5. Probe the TAC motor control 1 and 2 circuits with the test lamp connected to battery voltage. Did the test lamp illuminate and remain illuminated on either circuit? If yes, go to step  9 . If no, go to next step.
  6. Turn OFF the ignition. Connect the test lamp between the TAC motor control 1 and battery ground. Observe the test lamp as you turn ON the ignition. Does the test lamp flash ON and then turn OFF? If yes, go to next step. If no, go to step  10 .
  7. Turn OFF the ignition. Connect a test lamp between the TAC motor control 2 circuit and battery ground. Observe the test lamp as you turn ON the ignition. Does the test lamp flash ON and then OFF? If yes, go to step  13 . If no, go to step  10 .
  8. Turn OFF the ignition. Disconnect the PCM connector that contains the TAC motor control circuits. Turn ON the ignition, with the engine OFF. Probe the TAC motor control 1 and 2 circuits with the test lamp connected to ground. Does the test lamp illuminate? If yes, go to step  11 . If no, go to step  14 .
  9. Turn OFF the ignition. Disconnect the PCM connector that contains the TAC motor control circuits. Probe the TAC motor control 1 and 2 circuits with the test lamp connected to battery voltage. Does the test lamp illuminate? If yes, go to step  12 . If no, go to step  14 .
  10. Turn OFF the ignition. Disconnect the PCM connector that contains the TAC motor controls circuits. Test TAC motor control 1 and 2 circuits for an open or high resistance. Repair the circuit as necessary. Did you find and correct the condition? If yes, go to step  17 . If no, go to step  14 .
  11. Repair the short to voltage on the circuit where the test lamp remained illuminated. After repairs, go to step  17 .
  12. Repair the short to ground on the circuit where the test lamp remained illuminated. After repairs, go to step  17 .
  13. Test for a poor connection or terminal tension at the throttle body connector. Did you find and correct the condition? If yes, go to step  17 . If no, go to step  15 .
  14. Test for a poor connection or terminal tension at the PCM. Did you find and correct the condition? If yes, go to step  17 . If no, go to step  16 .
  15. Replace the throttle body assembly. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  17 .
  16. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  17. 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 .
  18. 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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