The immobilizer module or the vehicle theft deterrent (VTD) module sends the fuel enable password to the engine control module (ECM) via the serial data circuit. The ECM then challenges this password. Both the ECM and immobilizer module perform a calculation on this challenge. If the calculated response from the immobilizer module equals the calculation performed by the ECM, the ECM will allow vehicle starting. The ECM will disable vehicle starting if any of the following conditions occur:

The engine control module (ECM) monitors the signal circuit of the engine oil pressure (EOP) sensor. When the oil pressure is high, the sensor is open, and the ECM senses a high signal voltage. When the oil pressure is low, the sensor is closed, and the ECM senses a low signal voltage.

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The Air Conditioning (A/C) system uses an A/C refrigerant pressure sensor mounted in the high pressure side of the A/C refrigerant system to monitor A/C refrigerant pressure. The Engine Control Module (ECM) uses this information to turn ON the engine coolant fans when the A/C refrigerant pressure is high and to keep the compressor disengaged when A/C refrigerant pressure is excessively high or low.

The Air Conditioning Pressure (ACP) sensor operates like other 3-wire sensors. The ECM applies a 5.0 volt reference and a sensor ground to the sensor. Changes in the A/C refrigerant pressure will cause the ACP sensor input to the ECM to vary. The ECM monitors the ACP sensor signal circuit and can determine when the signal is outside of the possible range of the sensor. When the signal is out of range for a prolonged period of time, the ECM will not allow the A/C compressor clutch to engage. This is done to protect the compressor.

Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection at the ECM.

Inspect the wiring harness for damage. If the harness appears to be OK, observe the A/C pressure display on the scan tool while moving the connectors and wiring harnesses related to the A/C Pressure sensor. A change in the A/C pressure display will indicate the location of the fault.

If DTC P0532 cannot be duplicated, reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to set occurs. This may assist in diagnosing the condition.

The Air Conditioning (A/C) system uses an A/C refrigerant pressure sensor mounted in the high pressure side of the A/C refrigerant system to monitor A/C refrigerant pressure. The Engine Control Module (ECM) uses this information to turn ON the engine coolant fans when the A/C refrigerant pressure is high and to keep the compressor disengaged when A/C refrigerant pressure is excessively high or low.

The Air Conditioning Pressure (ACP) sensor operates like other 3-wire sensors. The ECM applies a 5.0 volt reference and a sensor ground to the sensor. Changes in the A/C refrigerant pressure will cause the ACP sensor input to the ECM to vary. The ECM monitors the ACP sensor signal circuit and can determine when the signal is outside of the possible range of the sensor. When the signal is out of range for a prolonged period of time, the ECM will not allow the A/C compressor clutch to engage. This is done to protect the compressor.

Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection at the ECM.

Inspect the wiring harness for damage. If the harness appears to be OK, observe the A/C pressure display on the scan tool while moving the connectors and wiring harnesses related to the ACP sensor. A change in the A/C pressure display will indicate the location of the fault.

If DTC P0533 cannot be duplicated, reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to set occurs. This may assist in diagnosing the condition.

The Engine Control Module (ECM) monitors the ignition voltage on the ignition feed circuit to terminal 39 at the ECM. A system voltage Diagnostic Trouble Code (DTC) will set whenever the voltage is below a calibrated value.

If the DTC sets when an accessory is operated, check for a poor connection or excessive current draw.

Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for the following conditions:

The Engine Control Module (ECM) monitors the ignition voltage on the ignition feed circuit to terminal 39 at the ECM. A system voltage Diagnostic Trouble Code (DTC) will set whenever the voltage is above a calibrated value.

If the DTC sets when an accessory is operated, check for a poor connection or excessive current draw.

Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for the following conditions:

The stop lamp switch signal circuit is a direct hardwire input to the engine control module (ECM) from the brake switch assembly. The ECM monitors the stop lamp switch signal circuit in order to detect when the brake pedal has been applied.

In order to avoid a misdiagnosis, inspect for proper operation of the stop lamps.

For an intermittent condition, refer to "Intermittents".