Normal Operation

Under normal operation, voltage is provided to the auxiliary coolant flow pump relay coil through circuit CBK03 (GY). When the HVAC module is ON, a message is sent over the Controller Area Network (CAN) to the PCM. When the PCM receives the message, a ground is provided to the auxiliary coolant flow pump relay coil from the PCM through circuit CH307 (GY/BU), energizing the auxiliary coolant flow pump relay.

An auxiliary coolant flow pump is used only on hybrid vehicles to improve engine coolant circulation at low engine speeds or when the engine is OFF.

The auxiliary coolant flow pump will be disabled when any of the following conditions are present:

• The climate control module is set to the OFF position.
• The ambient temperature is above 32°C (90°F).
• The coolant temperature is less than -10°C (14°F).
• The engine speed is above 4,000 rpm.

For a complete explanation of the auxiliary coolant flow pump refer to HEATING AND VENTILATION .

• DTC P2600 (Coolant Pump A Control Circuit/Open) - The DTC sets when the PCM grounds the relay circuit and excessive current draw is detected on the relay circuit. The DTC also sets when the relay circuit is OFF and no voltage is detected on the relay control circuit. The PCM expects to detect voltage coming through the relay coil to the relay circuit when it is not grounding it.

  This pinpoint test is intended to diagnose the following: 

• Wiring, terminals or connectors
• A/C clutch relay
• PCM