Chevrolet Silverado / GMC Sierra. Service manual — part 2350

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0532

Air Conditioning A/C Refrigerant Pressure Sensor Circuit Low Voltage

DTC P0533

Air Conditioning A/C Refrigerant Pressure Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit/System Description

The engine control module (ECM) monitors the high side refrigerant pressure through the A/C
refrigerant pressure sensor. The ECM supplies a 5-volt reference and a low reference to the
sensor. Changes in the A/C refrigerant pressure cause the sensor signal to the ECM to vary. When
the pressure is high, the signal voltage is high. When the pressure is low, the signal voltage is low.
When pressure is high, the ECM commands the cooling fans on. When pressure is too high or too
low, the ECM will not allow the A/C compressor clutch to engage.

Conditions for Running the DTC

Engine is running.

Any of the conditions for setting the DTC are met for 15 seconds.

Battery voltage is between 11-18 volts.

Conditions for Setting the DTC

The ECM detects that the A/C pressure is less than 1 psi (0.01 volt) sets DTC P0532.

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

5-Volt Reference

P0532

P0532

-

-

A/C Refrigerant Pressure Sensor
Signal

P0532

P0532

P0533

-

Low Reference

-

P0533

-

-

2008 Chevrolet Silverado 1500

2008 HVAC HVAC - Manual - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

The ECM detects that the A/C pressure is more than 428 psi (4.92 volts) sets DTC P0533.

Action Taken When the DTC Sets

The ECM will not illuminate the malfunction indicator lamp (MIL).

The ECM stores the Failure Records.

The A/C compressor clutch is disabled.

Conditions for Clearing the DTC

The history DTC will clear after 40 consecutive ignition cycles have occurred without a
malfunction.

The DTC will become history if the ECM no longer detects a failure.

Diagnostic Aids

A malfunction within the refrigerant system causing high pressure can cause this DTC to set.

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Air Temperature Description and Operation

Air Delivery Description and Operation

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Scan Tool Reference

2008 Chevrolet Silverado 1500

2008 HVAC HVAC - Manual - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the scan tool A/C Pressure Sensor parameter. The reading should be
between 0.1 volts (1 psi) and 4.90 volts (425 psi) and change with A/C refrigerant pressure
changes.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the A/C refrigerant pressure sensor.

2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 1 and

ground.

If greater than the specified range, test the low reference circuit for an open/high
resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 2 and

ground.

If less than the specified range, test the 5-volt reference circuit for a short to ground or
an open/high resistance. If the circuit tests normal, replace the ECM.

If greater than the specified range, test the 5-volt reference circuit for a short to
voltage. If the circuit tests normal, replace the ECM.

4. Verify the scan tool A/C High Side Pressure Sensor parameter is less than 0.1 volts (1 psi).

If greater than the specified range, test the signal circuit terminal 3 for a short to
voltage. If the circuit tests normal, replace the ECM.

5. Install a 3A fused jumper wire between the signal circuit terminal 3 and the 5-volt reference

circuit terminal 2. Verify the scan tool A/C High Side Pressure Sensor parameter is greater
than 4.90 volts (425 psi).

If less than the specified range, test the signal circuit for short to ground or an
open/high resistance. If the circuit tests normal, replace the ECM.

6. If all circuits test normal, test or replace the A/C refrigerant pressure sensor.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement (Non-HP2)

Control Module References for the ECM replacement, setup, and programming

DTC P0645

2008 Chevrolet Silverado 1500

2008 HVAC HVAC - Manual - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0645

A/C Clutch Relay Control Circuit

Diagnostic Fault Information

Circuit System Description

Ignition voltage is supplied directly to the A/C compressor clutch relay. The engine control
module (ECM) controls the relay by grounding the A/C clutch relay control circuit. When the
ECM is commanding a component ON, the voltage of the control circuit should be near 0 volt.
When the ECM is commanding the control circuit to a component OFF, the voltage potential of
the circuit should be near battery voltage.

Conditions for Running the DTC

The ignition voltage is between 11-18 volts.

The engine speed is greater than 600 RPM.

An A/C request is made.

Conditions for Setting the DTCs

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

B+

1

1

-

-

A/C Relay Coil Side Supply
Voltage

1

1

-

-

Ignition 1

1

1

-

-

A/C Compressor Clutch Relay
Control

P0645

P0645

P0645

-

A/C Relay Coil Side Ground

-

1

-

-

1. A/C Compressor Inoperative

2008 Chevrolet Silverado 1500

2008 HVAC HVAC - Manual - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado