HVAC System - Automatic: Diagnosis GMC Sierra 3500 HD

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

Diagnostic Fault Information

Diagnostic Aids

Ambient Air Temperature Display Update

Conditions for Running the DTC

Ignition ON.

Conditions for Setting the DTC

The HVAC control module detects the temperature sensor signal circuit is less than -35°C (-39°F) or greater than 85°C (185°F) for greater than 15 seconds.

Action Taken When the DTC Sets

The system operates using a default value.

Conditions for Clearing the DTC

1. The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
2. The history DTC will clear after 100 fault-free ignition cycles.

Component Testing

1. A thermometer can be used to test the sensor off the vehicle in warn and or cold water. Refer to «Sensor Resistance Table»(ref-317150-S28856156442009060900000) for this test.
2. Test the evaporator air temperature sensor by varying the sensor temperature while monitoring the sensor resistance.
3. Compare the readings with the Temperature VS Resistance table and verify that the resistance is within 5 percent of the specification. If not within the specified range, replace the sensor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

Circuit Description

The sunload sensor is a 2-wire photo diode. The vehicle uses left and right sunload sensors. The two sensors are integrated into the sunload sensor assembly along with the ambient light sensor. Ground and signal circuits enable the sensors to operate. As the sunload increases, the sensor signal decreases. The sensor signal varies between 0 and 5 volts. The HVAC control module converts the signal to a range between 0 and 255 counts. The sunload sensor provides the HVAC control module with a measurement of the amount of light shining on the vehicle. Bright or high intensity light causes the vehicles interior temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle.

The following DTCs are for the left and right sunload sensors.

1. B0183 is for the left sunload sensor.
2. B0188 is for the right sunload sensor.

Ignition ON.

The HVAC control module detects the signal circuit is less than 5 counts or greater than 250 counts.

1. The driver information center (DIC) will display SERVICE A/C SYSTEM.
2. The system will operate as if no sunload condition exists.

1. The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
2. The history DTC will clear after 100 fault-free ignition cycles.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the sunload sensor.
2. Test for less than 10 ohms between the ground circuit terminal C and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, test for 4.8-5.2 volts between the ground circuit terminal C and the appropriate signal circuit terminal listed below: Left solar load sensor circuit terminal A. Right solar load sensor circuit terminal B. If less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the HVAC control module. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.
4. If all circuits test normal, test or replace the sunload sensor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. Ignition ON.
2. The HVAC module is ON.

The actual door position differs from the commanded door position by more than 4 counts or the HVAC control module detects the door position signal circuit is less than 3 counts or greater than 253 counts.

The control circuit is deactivated for the appropriate actuator.

1. The DTC becomes history when the HVAC control module no longer detects the condition that set the DTC.
2. The history DTC will clear after 100 fault-free ignition cycles.

1. Ignition OFF, disconnect the harness connector at the appropriate actuator.
2. Test for less than 1 ohm between the low reference circuit terminal 7 and ground. If greater than the specified range, test the low reference circuit for an open/high resistance.
3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 10 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 greater than the specified range, test the 5-volt reference circuit for a short to voltage.
4. Verify the appropriate scan tool parameter is less than 4 counts. If greater than the specified range, test the signal circuit terminal 9 for a short to ground.
5. Install a 3-amp fused jumper wire between the signal circuit terminal 9 and the low reference circuit terminal. Verify the appropriate scan tool parameter is greater than 250 counts. If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance.
6. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 5 and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
7. Install a DMM between the actuator control circuit terminal 6 and ground. While monitoring the DMM, use the scan tool to command the appropriate actuator from one direction to the other. The voltage on the control circuit should move from 0 volts in one direction to 5 volts in the other direction and 2.5 volts in the at rest state. If the voltage does not change, test the control circuit for an open, short to voltage or short to ground. If circuit tests normal replace the HVAC control module.
8. If all circuits test normal, replace the actuator.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

Battery voltage is between 9-16 volts and data link communications operate normally.

The HVAC control module has internal fault inside the HVAC control module for a stuck or shorted control button.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. Engine is running.
2. Any of the conditions for setting the DTC are met for 15 seconds.
3. Battery voltage is between 11-18 volts.

1. The ECM detects that the A/C pressure is less than 1 psi (0.01 volt) sets DTC P0532.
2. The ECM detects that the A/C pressure is more than 428 psi (4.92 volts) sets DTC P0533.

1. The ECM will not illuminate the malfunction indicator lamp (MIL).
2. The ECM stores the Failure Records.
3. The A/C compressor clutch is disabled.

1. The history DTC will clear after 40 consecutive ignition cycles have occurred without a malfunction.
2. The DTC will become history if the ECM no longer detects a failure.

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

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.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. The ignition voltage is between 11-18 volts.
2. The engine speed is greater than 600 RPM.
3. An A/C request is made.

The ECM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data.

A history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction.

1. Ignition OFF, disconnect the A/C relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 and ground. If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the ignition circuit terminal 85 and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or a open/high resistance. If the circuit tests normal and ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.
4. Verify that a test lamp illuminates between the relay B+ circuit terminal 30 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or a open/high resistance. If the circuit tests normal and B+ circuit fuse is open, replace the A/C clutch relay.
5. Disconnect the harness connector at the A/C clutch coil.
6. Test for less than 1 ohm between the ground circuit terminal 2 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the A/C clutch coil.
8. Connect a 10-amp fused jumper wire between the B+ circuit terminal 30 and control circuit terminal 87. Verify the A/C clutch is activated. If the A/C clutch does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the A/C clutch.
9. Connect a test lamp between the ignition circuit terminal 85 and the control circuit terminal 86.
10. Command the A/C relay output function ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM. If the test lamp is always OFF, test the control circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the ECM.
11. If all circuits test normal, test or replace the A/C clutch relay.

1. Ignition OFF, disconnect the A/C COMP relay.
2. Test for 60-180 ohms between terminals 85 and 86. If the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 If not the specified value, replace the relay.
4. Install a 30-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87. If greater than the specified range, replace the relay.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

An A/C request is received from the HVAC module.

A short to voltage, short to ground, or open/high resistance is seen on the A/C compressor clutch relay control circuit.

DTC P0646 and DTC P0647 are Type C DTCs

DTC P0646 and DTC P0647 are Type C DTCs

1. Ignition OFF, disconnect the A/C relay.
2. Ignition ON, verify a test lamp illuminates between the relay coil B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
3. Connect a test lamp between the relay coil B+ circuit terminal and the A/C compressor clutch relay control circuit terminal.
4. Engine running, command the A/C relay ON and OFF. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM/PCM. If the test lamp is always OFF< test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM/PCM.
5. If all circuits test normal, test or replace the A/C relay.

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the HVAC System. Refer to «Checking Aftermarket Accessories»(ref-317172-S31262273302009060900000) .
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Verify the A/C compressor clutch turns freely and is not seized.
4. The A/C compressor will not operate in cold outside air temperatures. Refer to «Air Temperature Description and Operation»(ref-317150-S38101332942009060900000) .
5. The following could cause window fogging: Wet carpet or mats High humidity Interior water leak Blocked A/C evaporator drain tube Maximum passenger capacity Blocked body pressure relief valves
6. Inspect the air distribution system for causes of reduced air flow: Obstructed or dirty passenger compartment air filter, if equipped Blocked or damaged air inlet or outlet vents

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Blower Motor Malfunction»(ref-317150-S04478754422009060900000)
2. «Air Conditioning Compressor Malfunction»(ref-317150-S37277130012009060900000)
3. «Air Temperature Malfunction»(ref-317150-S05075409982009060900000)
4. «Leak Testing»(ref-317146-S09866554032009060900000)
5. «Noise Diagnosis - HVAC Module»(ref-317146-S24273064492009060900000)
6. «Noise Diagnosis - Air Conditioning (A/C) System»(ref-317146-S07308588592009060900000)
7. «Noise Diagnosis - Blower Motor»(ref-317146-S39424128522009060900000)
8. «Odor Diagnosis»(ref-317146-S36356393212009060900000)

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

The following conditions must be met in order for the ECM to turn on the compressor clutch

1. Battery voltage is between 9-18 volts
2. Engine coolant temperature (ECT) is less than 123°C (253°F)
3. Engine speed is greater than 600 RPM
4. Engine speed is less than 4,760 RPM
5. A/C high side pressure is between 2929-269 kPa (39-425 psi)
6. Throttle position is less than 100 percent
7. Evaporator temperature is greater than 0°C (32°F)
8. ECM does not detect excessive torque load
9. ECM does not detect insufficient idle quality
10. The ambient temperature is above 1°C (34°F)

1. Ignition OFF, disconnect the harness connector at the A/C low pressure switch.
2. Test for less than 5 ohms between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Low Pressure Switch parameter is Open. If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module
4. Connect a 3A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool Low Pressure Switch parameter is Closed. If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module
5. Connect the harness connector at the A/C low pressure switch. Verify the scan tool Low Pressure Switch parameter is Closed. If not the specified value, test or replace the A/C low pressure switch.
6. Ignition OFF, disconnect the A/C relay.
7. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 and ground. If the test lamp illuminates, test the control circuit for a short to voltage.
8. Verify that a test lamp illuminates between the ignition circuit terminal 85 and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or a open/high resistance. If the circuit tests normal and ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.
9. Verify that a test lamp illuminates between the relay B+ circuit terminal 30 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or a open/high resistance. If the circuit tests normal and B+ circuit fuse is open, replace the A/C clutch relay.
10. Disconnect the harness connector at the A/C clutch coil.
11. Test for less than 1 ohm between the ground circuit terminal 2 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
12. Connect the harness connector at the A/C clutch coil.
13. Connect a 10A fused jumper wire between the B+ circuit terminal 30 and control circuit terminal 87. Verify the A/C clutch is activated. If the A/C clutch does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the A/C clutch.
14. Connect a test lamp between the ignition circuit terminal 85 and the control circuit terminal 86.
15. Command the A/C relay output function ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM. If the test lamp is always OFF, test the control circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the ECM.
16. If all circuits test normal, test or replace the A/C clutch relay.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. Ignition OFF, disconnect the X2 harness connector at the blower motor control module.
2. Test for less than 1.0 ohm between the ground circuit terminal 5 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 6 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse (HVAC BLWR 40-amp) in the underhood fuse block is open, test all components connected to the B+ circuit and replace as necessary.
4. Connect a DMM between the control circuit terminal 3 and ground.
5. Cycle the blower motor from OFF to HIGH. The voltage should increase while changing between the commanded states. If voltage remains greater than 11.5 volts while changing between the commanded states, test the control circuit for a short to voltage. If the circuit test normal, replace the HVAC control module. If voltage remains less than 1.0 volts while changing between the commanded states, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module. If voltage is between 1.0-11.5 volts and does not increase when changing between the commanded states, replace the HVAC control module.
6. Ignition OFF, connect the X2 harness connector at the blower motor control module. Disconnect the harness connector at the blower motor.
7. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal A and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the blower motor control module.
8. Connect a test lamp between the control circuit terminal B and the B+ circuit terminal A.
9. Turn the blower motor on high speed then to low speed. The test lamp intensity should be bright when in high speed and very dim or off when the blower is on low speed. If the test lamp intensity does not vary, test the control circuit for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the blower motor control module.
10. If all circuits test normal, test or replace the blower motor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

Ambient Air Temperature Display Update

1. Ignition OFF, disconnect the harness connector at the appropriate temperature sensor.
2. Test for the appropriate resistance between the signal terminal A or 1 and the low reference terminal B or 2. Refer to «Sensor Resistance Table»(ref-317150-S28856156442009060900000) for resistance values.

1. If not within the specified range, replace the appropriate sensor.

Preferred Method (w/Scan Tool)

1. Clear all DTCs.
2. Place the ignition switch in the OFF position.
3. Install the HVAC actuator.
4. Connect all previously disconnected components.
5. Start the vehicle.
6. With the scan tool, initiate the Motor Re-calibration feature of the Heating and Air Conditioning Special Functions menu.
7. Verify that no DTCs have set as current DTCs.

Alternate Method (w/o Scan Tool)

1. Clear all DTCs.
2. Place the ignition switch to the OFF position.
3. Install the HVAC actuator.
4. Connect all previously disconnected components.
5. Remove the HVAC/ECAS fuse for a minimum of 10 seconds.
6. Install the HVAC/ECAS fuse.
7. Start the vehicle.
8. Wait 40 seconds for the HVAC control module to self-calibrate.
9. Verify that no DTCs have set as current DTCs.

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