Coolant Pump "A" Control Circuit High
The PCM detected an excessively high voltage signal in the Coolant Pump A control circuit, indicating an electrical fault preventing proper pump operation. This typically occurs in vehicles with electric coolant pumps and can cause the cooling system to malfunction, forcing cooling fans to run continuously.
What You Might Notice
- Engine overheating or running hot
- Cooling fans running continuously at full speed
- Reduced fuel economy due to constant fan operation
- Check Engine Light illuminated
- Potential loss of electric coolant pump control
Most Common Causes
- 1
Wiring or connector fault
Damaged, corroded, or loose wiring in the coolant pump control circuit or a faulty connector can cause voltage signal abnormalities. Check for water intrusion, corrosion, or poor connections.
- 2
Coolant pump motor failure
The electric coolant pump motor may have an internal short or winding failure that prevents proper signal transmission. This causes the PCM to see an abnormal high voltage condition.
- 3
PCM or control module fault
A defective powertrain control module or coolant pump control relay may incorrectly interpret circuit voltage or fail to properly regulate pump operation.
- 4
Ground wire failure
A loose or disconnected ground wire in the coolant pump circuit prevents proper voltage regulation and causes the PCM to detect a high voltage fault condition.
How to Diagnose It
- 1
Check Wiring or connector fault — Damaged, corroded, or loose wiring in the coolant pump control circuit or a faulty connector can cause voltage signal abnormalities. Check for water intrusion, corrosion, or poor connections.
- 2
Check Coolant pump motor failure — The electric coolant pump motor may have an internal short or winding failure that prevents proper signal transmission. This causes the PCM to see an abnormal high voltage condition.
- 3
Check PCM or control module fault — A defective powertrain control module or coolant pump control relay may incorrectly interpret circuit voltage or fail to properly regulate pump operation.
- 4
Check Ground wire failure — A loose or disconnected ground wire in the coolant pump circuit prevents proper voltage regulation and causes the PCM to detect a high voltage fault condition.
How to Fix It
- 1
Inspect and repair wiring and connectors
Visually inspect the coolant pump control circuit wiring for damage, corrosion, or loose connections. Test connector terminals for proper contact and repair or replace any damaged wiring.
- 2
Test and replace coolant pump motor
Use a multimeter to test the coolant pump motor for proper resistance and continuity. If the motor shows signs of internal short or failure, replace the entire pump assembly.
- 3
Check and repair ground connections
Locate the ground wire for the coolant pump circuit and ensure it is firmly connected and free from corrosion. Clean corrosion off terminals and tighten connections.
- 4
Test and reprogram PCM or replace control relay
If wiring and pump are confirmed good, have the PCM scanned for internal faults or reprogram it if needed. Test the coolant pump relay for proper function and replace if defective.
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