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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1385 (Engine Controls And Fuel - 6.6L - DTC P1448 To DTC P2510) >> DTC P2122, P2123, P2127, P2128, or P2138 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at the APP sensor.
  2. Ignition OFF and scan tool disconnected for 90 seconds, test for less than 5 Ω of resistance between the appropriate low reference circuit listed below and ground:
    • APP sensor 1 terminal F
    • APP sensor 2 terminal A
    • If greater than the specified range, test the affected low reference circuit for an open/high resistance. If the circuit connections test normal, replace the ECM.
  3. Ignition ON, test for 4.8-5.2 V between the appropriate 5 V reference circuit listed below and ground:
    • APP sensor 1 terminal D
    • APP sensor 2 terminal C
    • If less than the specified range, test the affected 5 V reference circuit for a short to ground or an open/high resistance. If the circuit connections test normal, replace the ECM.
  4. Verify that the scan tool APP Sensor 1 and APP Sensor 2 parameters are less than 0.02 V.
    • If greater than 0.02 V, test the applicable signal circuit terminals B or E for a short to voltage. If the circuit tests normal, replace the ECM.
  5. Install a 3 A fused jumper wire between each signal circuit terminals B or E and the 5 V reference circuit. Verify that the scan tool APP Sensor parameter is greater than 4.57 V.
    • If less than the specified range, test the applicable signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  6. Ignition OFF, disconnect the X1 and X2 harness connectors at the ECM.
  7. Test for less than 5 Ω of resistance on all APP sensor circuits between the following terminals:
    • The ECM X2 signal circuit terminal 49 to APP terminal E
    • The ECM X1 signal circuit terminal 21 to APP terminal B
    • The ECM X1 5 V reference circuit terminal 38 to APP terminal C
    • The ECM X2 5 V reference circuit terminal 15 to APP terminal D
    • If greater than the specified range, repair the affected circuit for open/high resistance.
  8. Test for infinite resistance between APP sensor 1 and 2 signal circuits.
    • If less than infinite resistance, repair the short between signal circuits.
  9. If all circuits test normal, test or replace the accelerator pedal assembly.
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