P1533

Circuit Description
The Air Conditioning (A/C) low side temperature sensor uses a thermistor to control the signal voltage to the PCM. The PCM applies 5 volts on CKT 731 to the sensor. When the sensor is cold, its resistance is high; therefore, the PCM will see a high signal voltage. As the sensor warms, its resistance becomes less and the signal voltage is pulled low through the ground, CKT 470. This diagnostic detects a shorted to ground or open A/C low side temperature sensor circuit by setting the DTC if the PCM monitors a signal voltage, temperature, that is too high or low.

Conditions for Running the DTC
^ Ambient Air Temperature between 4°C (39°F) and 99°C (210°F).
^ Ambient Air Temperature sensor failure not indicated by the HVAC controller.

Conditions for Setting the DTC
A/C low side temperature sensor reads less than -37°C (-35°F) or more than 99°C (210°F).

Action Taken When the DTC Sets
Disable the A/C compressor clutch.
^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ No message will be displayed.

Conditions for Clearing the DTC
^ A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
^ A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
^ Use a scan tool to clear DTCs.
^ Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended.

Diagnostic Aids
With the vehicle engine not running and at ambient temperature the A/C temperature sensor should also be near ambient temperature. If the A/C temperature sensor is not near ambient temperature check for a sensor or circuit with resistance that is too high or too low. A sensor temperature reading that is too high would indicate a shorted or low resistance sensor or circuit. A sensor temperature reading that is too low would indicate an open or high resistance sensor or circuit.