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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 P0403, P0404, P0405, P0406, or P042E >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
IMPORTANT: You must complete the Circuit/System Verification before proceeding with Circuit/System Testing.
  1. Ignition OFF, disconnect the EGR valve harness connector.
  2. Ignition ON, connect a test lamp between B+ and the EGR low control circuit. The test lamp should illuminate.
    • If the test lamp does not illuminate, test the EGR low control circuit for an open/high resistance. If the circuit tests normal, replace the PCM.
  3. Connect a test lamp between the EGR high control circuit and ground. Command the EGR valve from 0-90 percent and exit the EGR Solenoid Output Control. The test lamp should turn ON when commanded between 10 and 90 percent and turn OFF when exiting the EGR Solenoid Output Control.
    • If the test lamp is ON after exiting the EGR Solenoid Output Control, test the EGR high control circuit for a short to voltage. If the circuit tests normal, replace the PCM.
    • If the test lamp is always OFF while commanding the EGR valve from 0-90 percent, test the EGR high control circuit for an open, high resistance, or a short to ground. If the circuit tests normal, replace the PCM.
  4. Ignition OFF, test for less than 5 ohm of resistance between the low reference circuit and ground.
    • If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the PCM.
  5. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit and ground.
    • If less than the specified range, test the 5-volt reference circuit for a short to ground, short to EGR Control circuits or an open/high resistance. If the circuit tests normal, replace the PCM.
    • If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the PCM.
  6. Verify the EGR Position parameter is less than 1 percent.
    • If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the PCM.
  7. Install a 3A fused jumper wire between the signal circuit and the 5-volt reference circuit. The EGR Position Sensor parameter should display more than 90 percent.
    • If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the PCM.
  8. If all circuits test normal, replace the EGR valve.
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