General Information

Engine Control

P0646 A/C Clutch Relay Control Circuit Low - General Information

General Description

The A/C compressor can be activated if the A/C switch is operated while the blower is running and system operation is enabled by the ECM. When A/C is requested, the Engine Control Module (ECM) provides a ground path to the A/C camp cut signal line. When the camp cut signal line is grounded, the A/C compressor can be energized. The ECM delays grounding the camp cut line for a short time, so the ECM can adjust the engine idle speed for the additional load. The ECM temporarily de-energizes the A/C compressor for one or more of the following conditions:
- Full acceleration when the throttle is at WOT.(Wide Open Throttle)
- Risk of overheating: Engine coolant temp. exceeds threshold value
- A/C system pressure exceeds threshold value
- Engine starting

DTC Description

If there is open or short to ground in A/C compressor cut off circuit, ECM sets DTC P0646.

DTC Detecting Condition





Specification





Diagnostic Circuit Diagram