DTC 05

CIRCUIT DESCRIPTION

The inside air temperature sensor (3) is a thermistor that provides a signal voltage to the control assembly microprocessor (15).

The microprocessor (15) supplies a reference voltage (about 5 volts) on CKT 734 to the sensor. When the inside air temperature is cold, the thermistor resistance is high; therefore, the microprocessor (15) will receive a high signal voltage input. If the inside air temperature is high, the thermistor resistance is low; therefore, the microprocessor (15) will receive a low signal voltage input.

TEST DESCRIPTION

The following numbers refer to circled numbers on the diagnostic chart.

1. This test will determine if the microprocessor (15) has defaulted to a default value of 128 which represents 10°C (75°F) and Code 08 will set if:

^ a high resistance (open) is present for more than 1.6 seconds, or the microprocessor (15) detects a large change in resistance in a short period of time, based on the microprocessor's error program.

2. This test will determine if the inside air temperature sensor (3) is within its correct range. The resistance varies with temperature. so the Diagnostic Aid Correction Chart must be used if inside temperature is not 16°C (59°F).

3. This test will determine if an open is present in the sensor ground circuit.

4. This test will determine if the malfunction is intermittent or an open is present in the 5-volt reference voltage to the inside air temperature sensor (3). Terminal C8 should be checked. If no voltage is present, replace the microprocessor (15).

DIAGNOSTIC AIDS

If Code 05 is not displayed in parameter -00 or no malfunction found through Step 4, monitor counts in pointer -02 while checking for open and ground in harness by moving harness. If no opens (248 counts) can be found, monitor inside air temperature sensor (3) at maximum cold and hot interior temperatures while driving vehicle. Replace inside air temperature sensor (3) if out of parameter.