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Home >> Buick >> 2007 >> Lucerne CX >> Repair and Diagnosis >> External Pages >> Different car >> Section 151 (Engine Control System - 3.8L - DTC P0451 To DTC P2120) >> DTC P0641 or P0651 >> Circuit/System Testing >> P0651

Circuit/System Testing: P0651

WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
  1. With the ignition OFF, disconnect the harness connector at the A/C pressure sensor.
  2. With the ignition ON, measure for 4.8-5.2 volts between the A/C pressure sensor 5-volt reference circuit and ground.
    • If within 4.8-5.2 volts, refer to Testing for Intermittent Conditions and Poor Connections .
    • If over 5.2 volts, test all 5-volt references circuits for a short to voltage. If all circuits tested are OK, replace the A/C pressure sensor.
    • If under 4.8 volts, turn OFF the ignition and test all 5-volt references circuits for a short to ground or any sensor low reference circuit.
  3. If all circuits tested are OK, replace the control module.
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