P0A04 critical

Motor Electronics Coolant Pump Control Circuit High

The P0A04 code means the vehicle's onboard diagnostic system has detected: Motor Electronics Coolant Pump Control Circuit High. This is a critical severity code.

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Keep driving?: Short distances only
DIY difficulty: hard
Estimated cost: $200 - $650 (parts and labor)

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Common Symptoms

Check Engine Light on
Hybrid system warning light
Coolant pump may run continuously
Possible overheating of motor electronics

Probable Causes (Ranked by Likelihood)

Short to power in coolant pump control circuit Very High
Failed relay for coolant pump High
Damaged wiring harness causing short to battery voltage Moderate
Failed hybrid control module pump driver Low

Step-by-Step Diagnostic Procedure

Check for voltage at the pump connector with the pump commanded off.
Inspect wiring for chafing against power sources that could cause a short to battery voltage.
Test the coolant pump relay for proper operation.
Disconnect the control module connector and recheck the circuit for shorts.

Frequently Asked Questions

What does circuit high mean for P0A04?

Circuit high means the hybrid control module detects higher than expected voltage on the coolant pump control circuit, usually indicating a short to battery voltage or a stuck relay.

Will the coolant pump run constantly with P0A04?

In some cases, a short to power can cause the pump to run continuously regardless of commands from the control module. This can drain the 12V battery if the vehicle sits.

How is P0A04 diagnosed?

A technician will use a multimeter to check for voltage at the pump connector when the pump should be off, then trace the wiring to find the source of the unwanted voltage.