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Home >> Pontiac >> 2008 >> Grand Prix GXP >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 5 (Engine Controls And Fuel - 3.8L - DTC P0385 To DTC P2108) >> DTC P1125, P2120, P2125, or P2138 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Ignition OFF for 90 seconds, disconnect the harness connector at the accelerator pedal.
  2. Test for less than 3 ohms of resistance between each low reference circuit terminals A and D and ground.
    • If greater than 3 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the throttle body assembly.
  3. Ignition ON, test for 4.8-5.2 volts between each 5-volt reference circuit terminals C and F and ground.
    • If less than 4.8 volts, test affected 5-volt reference circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the throttle body assembly.
    • If greater than 5.2 volts, test affected 5-volt reference circuit for short to voltage. If the circuit tests normal, replace the throttle body assembly.
  4. Ignition ON, verify the scan tool APP sensor 1 and 2 voltages are less than 0.1 volt.
    • If greater than 0.1 volt, test the APP sensor 1 and 2 signal circuits terminals B and E for a short to voltage. If the circuit tests normal, replace the throttle body assembly.
  5. Install a 3A fused jumper wire between the signal circuit terminal E and the 5-volt reference circuit terminal F of the APP sensor 1, verify the APP sensor 1 voltage is greater than 4.8 volts.
    • If less than 4.8 volts, test the APP sensor 1 signal circuit for an open or short to ground. If the circuit tests normal, replace the throttle body assembly.
  6. Install a 3A fused jumper wire between the signal circuit terminal B and the 5-volt reference circuit terminal C of the APP sensor 2. Verify that the APP sensor 2 voltage is greater than 4.8 volts.
    • If less than 4.8 volts, test the APP sensor 2 signal circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the throttle body assembly.
  7. Ignition OFF for 90 seconds, disconnect the harness connector at the throttle body assembly.
  8. Test for less than 5 ohms of resistance on all APP sensor circuits between the following terminals:
    • Throttle body assembly low reference circuit terminal 2 to APP terminal A
    • Throttle body assembly low reference circuit terminal 12 to APP terminal D
    • Throttle body assembly signal circuit terminal 3 to APP terminal E
    • Throttle body assembly signal circuit terminal 11 to APP terminal B
    • Throttle body assembly 5-volt reference circuit terminal 1 to terminal C
    • Throttle body assembly 5-volt reference circuit terminal 13 to terminal F
    • If greater than 5 ohms, repair the affected circuit.
  9. Test for infinite resistance between APP sensor 1 signal circuit terminal E and APP sensor 2 signal circuit terminal B.
    • If less than infinite resistance, repair the short between APP sensor 1 signal circuit and APP sensor 2 signal circuits.
    • If all circuits test normal, replace the accelerator pedal.
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