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Normal Operation

Under normal operation, when A/C is requested in Electronic Automatic Temperature Control (EATC) or Dual Automatic Temperature Control (DATC) systems, a message is sent over the Medium Speed Controller Area Network (MS-CAN) bus to the Instrument Cluster (IC), then from the IC through the High Speed Controller Area Network (HS-CAN) bus to the PCM; or a voltage is sent to the IC through circuit CH434 (GY/YE), then a message is sent from the IC through the HS-CAN bus to the PCM Electronic Manual Temperature Control (EMTC) systems.

Ignition voltage for the A/C clutch relay switch is provided through circuit SBB25 (RD). When the PCM energizes the relay, ignition voltage is supplied to the A/C clutch through circuit CH401 (VT/WH). Ground is supplied for the A/C clutch through circuit GD121 (BK/YE).

This pinpoint test is intended to diagnose the following:

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