A/C Water Pump Detection Circuit Failure
Code B1968 indicates a failure in the A/C water pump detection circuit, specific to Toyota/Lexus vehicles. This electric water pump circulates coolant through the evaporator heat exchanger when the engine is off or in stop/start mode. The A/C control module monitors the pump's feedback circuit and has detected an abnormal voltage or status signal, preventing verification of proper pump operation.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty or seized A/C water pump
- Damaged, corroded, or loose wiring in the detection circuit
- Moisture or corrosion in the water pump connector
- Internal pump detection resistor out of specification
- Faulty A/C control module (amplifier or climate ECU)
- Blown A/C water pump fuse
3. Symptoms You Will Notice
- A/C system may not cool when engine is off or in stop/start mode
- Possible A/C system warning light or reduced cooling performance
4. Step-by-Step Diagnosis
Check for blown A/C water pump fuse
Inspect wiring and connector for damage, corrosion, or loose connections
Test water pump resistance and voltage supply per service manual
Verify pump operation by commanding it on with a scan tool
If pump and wiring are okay, suspect A/C control module failure
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive, but the A/C may not cool properly when the engine is off or in stop/start mode. The vehicle remains drivable.
How much does it cost to fix?▼
Repair costs typically range from $200 to $800, depending on whether the pump or control module needs replacement and labor rates.