2017 Mazda MX-5 Rf OBD2 Code B1946 Climate Control A/C Post Evaporator Sensor Circuit Failure

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 2017 Mazda MX-5 rf 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 2017 Mazda MX-5 rf'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 2017 Mazda MX-5 rf 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:

• Repair or replace damaged or shorted electrical wiring and related components
• Replace the damaged or defective evaporator temperature sensor
• Replace damaged or defective DATC unit
• Clear all codes, test-drive your 2017 Mazda MX-5 rf, and rescan to see if any codes reappear

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 2017 Mazda MX-5 rf 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.

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B1946