B1946 OBD-II Trouble Code: Climate Control A/C Post Evaporator Sensor Circuit Failure

diagnostic check engine light

B1946 code definition

The B1946 code is a manufacturer specific body code related to the climate control system. In this case, the engine control module (ECM) has detected a failure in the evaporator temperature sensor for the climate control system or A/C.

What the B1946 code means

A code B1946 will be stored when the ECM detects a voltage signal from the post evaporator sensor that is signalling a failure (the signal should be approximately 5 volts depending on vehicle make and model).

Under normal operation, the LH and RH discharge temperature sensors receive a ground from the Dual Automatic Temperature Control (DATC) module. The evaporator discharge temperature sensor receives a ground from the DATC module. A 5-volt reference voltage is supplied to the LH and RH discharge temperature sensors from the DATC module. A 5- volt reference voltage is supplied to the evaporator discharge temperature sensor from the DATC module.

What causes the B1946 code?

Several problems may cause a B1946 code including:

  • Malfunctioning, damaged, or defective evaporator temperature sensor
  • Damaged or defective climate control unit
  • An open or shorted circuit in the wiring harness between the climate control unit and evaporator temperature sensor

What are the symptoms of the B1946 code?

Symptoms of a B1946 code may include:

  • Check engine or warning light may illuminate
  • Climate control or A/C may not blow cold air
  • Climate control or A/C may not work at all
  • There may be no symptoms other than a stored B1946 code

How does a mechanic diagnose the B1946 code?

A mechanic may use several methods to diagnose a B1946 trouble code, including:

  • Utilize an OBD-II scanner to check for a stored B1946 trouble code
  • Visually inspect wiring and electrical components related to the evaporator temperature sensor for signs of damage
  • Visually inspect the evaporator temperature sensor for signs of damage
  • Test the resistance on the evaporator temperature sensor (resistance should be measured compared with temperature ranges)
  • Check the DATC sensor output voltage (it should be between 4.7 and 5.1 volts)
  • Disconnect climate control unit and evaporator temperature sensor connector and check for an open circuit that has less than 5 ohms resistance
  • Check return circuit for an open or short circuit
  • Check reference circuit for a short to ground
  • Check reference circuits for a short to the return circuits

How serious is the B1946 code?

Because a vehicle’s safe driving operation most likely will not be impacted due to faults that store a B1946 code, this code is not considered to be a serious code. When this code appears, it is recommended to take your vehicle to your local service center or mechanic for repair and diagnosis as soon as possible.

What repairs can fix the B1946 code?

Several repairs can fix a B1946 trouble code and include:

Additional information related to a B1946 code

It is always recommended to take all proper safety precautions when working with the electrical components of your vehicle and to carefully follow service instructions. With more complicated electrical repairs, it is recommended to seek assistance from a professional.

In addition, note that the evaporator core, driver side heater core, and passenger side heater core discharge air temperature sensors have the same diagnostic procedure.

Need help with a B1946 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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