B0166

CIRCUIT DESCRIPTION
The Passenger Compartment Air Sensor is located in Control Head of HVAC module behind a small grille. In this position it is exposed to the air present in the passenger compartment. This provides a sample of the inside air temperature. The sensor is a thermistor used to control signal voltage at the heater and A/C control. The heater and A/C control supplies a reference voltage (about 5 volts internally) to sensor and measures voltage drop in the circuit to obtain a temperature signal. This signal is an input that tells the heater and A/C control how much cooling or heating will be required to deliver to passenger compartment.

When inside air temperature is cold, thermistor resistance is high: therefore the heater and A/C control will receive a high signal voltage input. If air temperature is hot thermistor resistance is low; the heater and A/C control will receive a low signal voltage input.

DTC PARAMETERS
^ Ignition in RUN position
^ Internal sensor circuit is shorted to battery voltage
^ Condition is present for 30 seconds
^ Counts are higher than 252

DIAGNOSTIC AIDS
Check the Aspirator tube connection to the automatic climate control head and the HVAC module.

TEST

Diagnostic Chart: