B1966 – A/C Post Heater Sensor Circuit Failure

The ODBII code B1966 indicates a malfunction in the A/C post heater sensor circuit, which may involve issues with the sensor itself, wiring, or connections affecting the air conditioning system’s performance.

The severity of ODBII code B1966 A/C Post Heater Sensor Circuit Failure is generally considered moderate.

Common Causes For: B1965 Seat Horizontal Forward/Rearward Potentiometer Feedback Circuit Short To Ground

• Faulty A/C post heater sensor
• Damaged wiring or connectors in the sensor circuit
• Short circuit or open circuit in the wiring
• Corroded connectors
• Poor ground connection
• Malfunctioning A/C control module
• Software issues in the vehicle’s control system

Common misdiagnosis for B1966 A/C Post Heater Sensor Circuit Failure

• Faulty A/C compressor
• Refrigerant leak
• Bad A/C control module
• Wiring issues or shorts in the harness
• Faulty temperature sensors
• Malfunctioning blower motor
• Incorrect A/C system charge
• Issues with the HVAC control panel

Common Troubleshooting Steps

The OBD-II code B1966 indicates a failure in the A/C post heater sensor circuit. This code is typically associated with issues in the air conditioning system, particularly with the sensor that monitors the post-heater operation. Here are some common troubleshooting steps to diagnose and resolve the issue:

• Check for Additional Codes: Use an OBD-II scanner to check for any other related trouble codes. This can provide more context and help identify if there are other issues affecting the A/C system.
• Inspect the A/C System:
• Check the A/C system for any visible signs of damage or leaks.
• Ensure that the refrigerant levels are adequate. Low refrigerant can affect sensor readings.
• Examine the A/C Post Heater Sensor:
• Locate the A/C post heater sensor and inspect it for physical damage, corrosion, or loose connections.
• Ensure that the wiring harness connected to the sensor is intact and free from fraying or breaks.
• Test the Sensor:
• Use a multimeter to test the resistance of the A/C post heater sensor. Compare the readings to the manufacturer’s specifications.
• If the sensor is out of specification, it may need to be replaced.
• Check the Wiring and Connectors:
• Inspect the wiring and connectors leading to the A/C post heater sensor for any signs of wear, corrosion, or poor connections.
• Repair or replace any damaged wiring or connectors.
• Inspect the A/C Control Module:
• If the sensor and wiring are in good condition, the issue may lie within the A/C control module. Check for any software updates or known issues with the module.
• If necessary, perform a reset of the A/C control module.
• Clear the Codes: After performing the necessary repairs or replacements, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the A/C system or the specific code B1966 for your vehicle make and model. Manufacturers may have specific recommendations or known fixes.
• Seek Professional Help: If the issue persists after following these steps, it may be best to consult a professional mechanic or technician who has experience with A/C systems and OBD-II diagnostics. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the B1966 code.