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Home >> GMC >> 2010 >> Terrain SLT, 2.4 W, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - 2.2L Or 2.4L - DTC P1255 To DTC P2635 >> DTC P1682 >> Circuit/System Testing

Circuit/System Testing

NOTE: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
  1. Ignition ON, observe the Ignition 1 Signal and the Engine Controls Ignition Relay Feedback Scan Tool parameters to determine which is more than 3 V lower than the other.
    2. NOTE: The ignition 1 signal is supplied by the ignition main relay. The engine controls ignition relay feedback signal is supplied by the engine control module relay.
  2. Ignition OFF, remove the relay that corresponds to the scan tool parameter that is more than 3 V lower.
    3. NOTE: A resistance of 6 Ω or greater in the circuit/underhood fuse block will cause the DTC to set.
  3. Connect a 20 A fused jumper wire between B+ and the applicable ignition voltage circuit terminal 30 leading to the K20 ECM. Ignition ON, verify that the applicable scan tool parameter displays between 9-14 V.
    • If the applicable scan tool parameter is less than the specified value, test the ignition voltage circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.
  4. Ignition OFF, connect a DMM set to the diode setting between the control circuit terminal 85 and ground. Verify the DMM displays OL.
    • If not the specified value, test the control circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.
  5. Ignition ON, verify the DMM displays less than 1 V.
    • If not the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
  6. If all circuits test normal, replace the applicable relay.
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