Code Definition

B1966 — A/C Post Heater Sensor Circuit Failure

System: Body  |  Type: Manufacturer-Specific  |  Make: Generic

About B1966

B1966 is a manufacturer-specific body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B1966 is stored, the module has detected a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

B1966 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The Climate Control Module monitors the A/C post heater temperature sensor to determine the temperature of air leaving the evaporator and entering the cabin after passing the heater core. The sensor is typically a negative temperature coefficient (NTC) thermistor whose resistance varies with the airstream temperature, producing a signal voltage the module uses to control blend door position and compressor cycling. DTC B1966 sets when the module detects that the sensor signal has failed in some way, either an open circuit, a short, or a value that falls outside the expected operating range. Whe...

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