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Home >> Buick >> 2008 >> Allure CXL >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 9 (Engine Control System & Fuel System - 3.6L - DTC P0335 To DTC P2097) >> DTC P0685, P0686, P0687, P0689, or P0690 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Ignition OFF, disconnect the PT relay.
  2. Ignition ON, load test for B+ between both of the PT relay circuit terminals C5, C6, and ground.
    • If less than the specified range, repair the appropriate circuit for a short to ground or an open/high resistance.
  3. Ignition OFF, connect a test lamp between the control circuit terminal A6 of the PT relay and B+. Verify the test lamp does not illuminate.
    • If the test lamp illuminates, test for a short to ground on the control circuit. If the circuit/connections test normal, replace the ECM.
  4. Ignition ON. Verify the test lamp illuminates when the ignition switch is cycled ON.
    • If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit. If circuit/connections test normal, replace the ECM.
    5. IMPORTANT: The ignition 1 voltage circuit is between the PT relay and the ECM. The ignition 1 voltage is a feedback circuit.
  5. Connect a 15A fused jumper wire between the B+ supply voltage circuit terminal C6, and the ignition 1 voltage circuit terminal A5, of the PT relay.
  6. Attempt to start the engine. The engine should start.
    • If the engine does not start, test the ignition 1 voltage circuit between the PT relay and the ECM for a short to ground or for an open/high resistance. If the circuit/connections test normal, replace the ECM.
  7. If all circuits/connections test normal, test or replace the PT relay.
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