HVAC System - Automatic: Diagnosis Cadillac STS I facelift

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit Description

The HVAC control module monitors the outside air quality via the air quality sensor assembly while in AUTO mode. The air quality sensor is a 5-wire sensor with a single ignition voltage circuit, a ground circuit, a low reference circuit, and two signal circuits. There are 2 sensors inside the air quality sensor assembly. A hydrocarbon (HC) sensor which is used for detecting gasoline exhaust fumes and a NOX sensor which is used for detecting oxides of nitrogen. When high levels of HC are detected at the front of the vehicle the HC sensor resistance and signal voltage are low. When high levels of NOX are detected at the front of the vehicle the Nox sensor resistance and signal voltage are high.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the air quality sensor.
2. Test for less than 5 ohms between the ground circuit terminal 6 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition OFF, test for less than 5 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 test normal test or replace the HVAC control module.
4. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 3 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
5. Test for 4.8-5.2 volts between the ground circuit terminal 6 and the signal circuit terminal 4. If less than the specified range, test the signal circuit for a open/high resistance. If the circuit tests normal, replace the HVAC control module.
6. Test for 4.8-5.2 volts between the ground circuit terminal 6 and the signal circuit terminal 2. If less than the specified range, test the signal circuit for a open/high resistance. If the circuit tests normal, replace the HVAC control module.
7. If all circuits test normal, test or replace the air quality sensor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.

Conditions for Running the DTC

Ignition ON.

Conditions for Setting the DTC

1. The HVAC control module detects the sensor signal circuit is less than -35°C (-39°F).
2. The HVAC control module detects the sensor signal circuit is greater than 85°C (185°F).

Action Taken When the DTC Sets

1. The HVAC control module uses a default air temperature value for further automatic control calculations. The default values are not displayed on the scan tool.
2. SERVICE A/C SYSTEM will be displayed on the DIC.

Conditions for Clearing the DTC

1. The DTC will become history if the HVAC control module no longer detects a failure.
2. The history DTC will clear after 50 fault-free ignition cycles.

1. Ignition OFF, disconnect the harness connector at the appropriate air temperature sensor.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal listed below and ground: Ambient air temperature sensor terminal B Inside air temperature sensor terminal 1 If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
3. Ignition ON, verify the scan tool appropriate Air Temp Sensor parameter is less than -35°C (-39°F). If greater than the specified range, test the signal circuit terminal listed below for a short to ground. If the circuit tests normal, replace the HVAC control module. Ambient air temperature sensor terminal A Inside air temperature sensor terminal 2
4. Install a 3A fused jumper wire between the signal circuit terminal listed below and the low reference circuit terminal listed below. Verify the scan tool Air Temp Sensor parameter is greater than 85°C (185°F). Ambient air temperature sensor signal circuit terminal A and low reference circuit terminal B Inside air temperature sensor signal circuit terminal 2 and low reference circuit terminal 1 If less than the specified range, 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. If all circuits test normal, test or replace the appropriate air temperature sensor.

Component Testing

1. Test the appropriate air temperature sensor by varying the sensor temperature while monitoring the sensor resistance.
2. Compare the readings with the Temperature VS Resistance table «Sensor Resistance Table»(ref-338123-S42476754312009081700000) , 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-338149-S41903538652009081700000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.

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 50 fault-free ignition cycles.

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-338149-S41903538652009081700000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of the diagnostic category.

1. Ignition ON.
2. Ignition voltage is between 9-16 volts.
3. 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 7 counts or greater than 250 counts.

Driver A and driver B circuits are 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 50 fault-free ignition cycles.

1. Disconnect the harness connector at the appropriate actuator.
2. Ignition OFF, test for less than 1 ohm between the low reference circuit terminal 1 and ground. If greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
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 HVAC control module. If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.
4. Verify the appropriate scan tool parameter is less than 4 counts. If greater than the specified range, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the HVAC control module.
5. Install a 3A fused jumper wire between the signal circuit terminal 3 and the low reference circuit terminal 1. 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. If the circuit tests normal, replace the HVAC control module.
6. Ignition ON, after 30 seconds verify that a test lamp illuminates between control circuit A terminal 5 and B+. If the test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal replace the HVAC control module.
7. Ignition OFF, verify that the test lamp does not illuminate between control circuit A terminal 5 and B+. If the test lamp illuminate, test the control circuit for a short to ground. If circuit tests normal replace the HVAC control module.
8. Ignition ON, after 30 seconds verify that a test lamp illuminates between control circuit B terminal 4 and B+. If the test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal replace the HVAC control module.
9. Ignition OFF, verify that the test lamp does not illuminate between control circuit B terminal 4 and B+. If the test lamp illuminate, test the control circuit for a short to ground. If circuit tests normal replace the HVAC control module.
10. If all circuits test normal, test or replace the actuator.

1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.

The HVAC control module monitors the outside air quality via the air quality sensor assembly while in AUTO mode. The air quality sensor is a 5-wire sensor with a single ignition voltage circuit, a ground circuit, a low reference circuit, and two signal circuits. There are 2 sensors inside the air quality sensor assembly. A hydrocarbon (HC) sensor which is used for detecting gasoline exhaust fumes and a NOX sensor which is used for detecting oxides of nitrogen. When high levels of HC are detected at the front of the vehicle the HC sensor resistance and signal voltage are low. When high levels of NOX are detected at the front of the vehicle the Nox sensor resistance and signal voltage are high.

1. Ignition ON
2. DTC B1325 is not set

The HVAC control module detects the air quality sensor signal that is less than 0.09 volt for more than 30 seconds

The driver information center (DIC) will display SERVICE A/C SYSTEM.

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 50 fault-free ignition cycles.

1. Ignition OFF, disconnect the harness connector at the air quality sensor.
2. Test for less than 5 ohms between the ground circuit terminal 6 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
3. Test for less than 5 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 test normal test or replace the HVAC control module.
4. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 3 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
5. Test for 4.8-5.2 volts between the ground circuit terminal 6 and the signal circuit terminal 4. If less than the specified range, test the signal circuit for a open/high resistance. If the circuit tests normal, replace the HVAC control module.
6. Test for 4.8-5.2 volts between the ground circuit terminal 6 and the signal circuit terminal 2. If less than the specified range, test the signal circuit for a open/high resistance. If the circuit tests normal, replace the HVAC control module.
7. If all circuits test normal, test or replace the air quality sensor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.

The HVAC control module supplies the evaporator air temperature sensor with a low reference circuit and 5-volt signal circuit. The HVAC control module determines the voltage drop across the sensor, which is proportional to temperature. As the air temperature increases, the sensor resistance decreases and the voltage signal decreases. As the air temperature decreases, the sensor resistance increases and the voltage signal increases.

Ignition ON.

The HVAC control module detects the evaporator air temperature sensor signal circuit is less than -36°C (-38°F) or more than 215°C (419°F) for more than 15 seconds.

1. The driver information center (DIC) will display SERVICE A/C SYSTEM.
2. The air conditioning (A/C) compressor will be disabled.

1. The DTC will become history if the HVAC control module no longer detects a failure.
2. The history DTC will clear after 50 fault-free ignition cycles.

1. Ignition OFF, disconnect the harness connector at the evaporator temperature sensor.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 2 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 HVAC control module.
3. Ignition ON, test for 4.8-5.2 volts between the low reference circuit terminal 2 and the signal circuit terminal 1. If less than the specified voltage, 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 voltage, 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 evaporator air temperature sensor.

1. Test the evaporator air temperature sensor by varying the sensor temperature while monitoring the sensor resistance.
2. Compare the readings with the Temperature VS Resistance table «Sensor Resistance Table»(ref-338123-S42476754312009081700000) 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-338149-S41903538652009081700000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of the 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).
2. The ECM detects that the A/C pressure is more than 428 psi (4.92 volts).

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.

Diagnostic Aids

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

1. Ignition OFF, disconnect the A/C pressure sensor harness connector.
2. Ignition OFF, test for less than 1 ohm 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 428 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 428 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 pressure sensor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.

1. The ignition voltage is between 9 and 18 volts.
2. The engine speed is more than 80 RPM.
3. The ECM A/C Compressor Clutch Relay Control transitions between ON to OFF or from OFF to ON.

1. A short to ground on the A/C compressor clutch relay control circuit.
2. A short to voltage on the A/C compressor clutch relay control circuit.
3. An open circuit on the A/C compressor clutch relay control circuit or relay.
4. An internally shorted or excessively low resistance A/C clutch relay coil.

1. The A/C clutch relay is commanded OFF.
2. The conditions for which the DTC was set will be stored in the Failure Records data only. No information will be stored as Freeze Frame data.

The history DTC will clear after 40 fault-free ignition cycles.

1. Ignition OFF, disconnect the A/C COMP relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 85 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 86 and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and ignition circuit fuse is open, test or replace the relay.
4. Connect a test lamp between the ignition circuit terminal 86 and the control circuit terminal 85.
5. Command the A/C relay 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.
6. If all circuits test normal, test or replace the A/C COMP 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 30A 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.

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the HVAC System. Refer to «Checking Aftermarket Accessories»(ref-338151-S01119782592009081700000) .
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. Verify that the customer is using the correct key to enable personalization and is not inadvertently activating auxiliary HVAC controls.
5. The A/C compressor will not operate in cold outside air temperatures.
6. The following conditions may 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
7. 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. «Air Conditioning Compressor Malfunction»(ref-338123-S09846400312009081700000)
2. «Blower Motor Malfunction»(ref-338123-S42589454422009081700000)
3. «Air Temperature Malfunction»(ref-338123-S39458877532009081700000)

1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) 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) «Air Conditioning (A/C) System Performance Test (LY7 w/ Heavy Duty Cooling)»(ref-338121-S30653505322009081700000) or «Air Conditioning (A/C) System Performance Test (LY7 w/Standard Cooling)»(ref-338121-S28385961702009081700000) or «Air Conditioning (A/C) System Performance Test (LC3)»(ref-338121-S29698943422009081700000) or «Air Conditioning (A/C) System Performance Test (LH2 w/ Heavy Duty Cooling)»(ref-338121-S35369336982009081700000) or «Air Conditioning (A/C) System Performance Test (LH2 w/ Standard Cooling)»(ref-338121-S13276897562009081700000) .
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 ON, with a scan tool, verify the A/C Switch parameter cycles between On and Off with each press of the A/C switch If the parameter does not cycle, replace the HVAC control module.
2. Remove the A/C CLTCH relay.
3. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
4. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground. If the test lamp does not illuminate, test the relay switch B+ circuit for an open/high resistance. If the A/C clutch fuse is open, test the relay switch control circuit for a short to ground. If all circuits test normal, test or replace the A/C compressor clutch.
5. Disconnect the harness connector at the A/C compressor clutch.
6. Ignition OFF test for less than 1.0 ohm between the A/C compressor 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 compressor clutch.
8. Connect a 10A fused jumper wire between the B+ circuit terminal 30 and the relay switch control circuit terminal 87. Verify the A/C compressor clutch engages. If the A/C compressor clutch does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the A/C compressor.
9. Connect a test lamp between the relay control circuit terminal 86 and the B+ circuit terminal 85.
10. Using a scan tool, command the A/C relay output ON and OFF. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp remains ON all the time, test for a short to ground on the control circuit connector X1 terminal 53. If the circuit tests normal, replace the ECM. If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit. If the circuit tests normal, replace the ECM.
11. If all circuits test normal, test or replace the A/C compressor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.

1. Ignition OFF, disconnect the BLOWER 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 B+ circuit terminal 87 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 BLOWER fuse is open, test the B+ circuit for a short to ground. If the circuit tests normal, replace the blower controller.
4. Connect a test lamp between the control circuit terminal 86 and B+.
5. Command the blower motor ON and OFF. The test lamp should turn ON and OFF when changing between the commanded states. 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 HVAC control module. If test lamp is always ON, test for short to ground. If circuit tests normal, replace the blower relay.
6. Connect the BLOWER relay.
7. Ignition OFF, disconnect the X2 harness connector at the blower controller.
8. Test for less than 1 ohm between the ground circuit terminal 5 and ground. If not the specified range, test the ground circuit for an open/high resistance.
9. Connect a test lamp between the B+ circuit terminal 6 and ground.
10. Turn ON the blower motor. Verify the test lamp illuminates. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. If the circuit tests normal, test or replace the BLOWER relay.
11. Install a test lamp between the control circuit terminal 3 and B+.
12. Turn the blower motor ON and cycle between low and high speeds. The test lamp should dimly illuminate at high speeds and reduce in intensity as the blower speed is reduced. If the test lamp does not illuminate, test the control circuit for short to voltage or an open/high resistance. If the circuits test normal, test or replace the HVAC control module. If the test lamp does not change intensity, test the control circuit for a short to ground. If the circuit tests normal, test or replace the HVAC control module.
13. Connect the harness connector at the blower controller.
14. Disconnect the harness connector at the blower motor.
15. Install at test lamp between the B+ circuit terminal 2 and ground.
16. Turn ON the blower motor. Verify the test lamp illuminates. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
17. Install a test lamp between the control circuit terminal 1 and the B+ circuit terminal 2.
18. Turn the blower motor ON and cycle between low and high speeds. The test lamp should illuminate and change in intensity as the blower speed is varied. If the test lamp does not illuminate, test the low reference circuit for short to voltage or an open/high resistance. If the circuit tests normal, test or replace the blower controller. If the test lamp does not change intensity, test the low reference circuit for a short to ground. If the circuit tests normal, test or replace the blower controller.
19. If all circuits test normal, test or replace the blower motor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.

Evaporator and Ambient Air Temperature Sensor Circuit Malfunction

1. Ignition OFF, disconnect the harness connector at the appropriate temperature sensor.
2. Ignition OFF, test for less than 10 ohms between the appropriate low reference circuit terminal and ground. Ambient air temperature sensor terminal B. Evaporator temperature sensor terminal 2. If greater than the specified range, test the low reference circuit for high resistance. If the circuit tests normal, replace the HVAC control module.
3. Ignition ON, test for 4.8-5.2 volts between the low reference circuit terminal B and the appropriate signal circuit terminal. Ambient air temperature sensor terminal A. Evaporator temperature sensor terminal 1. If less than the specified range, test the signal circuit for high resistance. If the circuit tests normal, replace the HVAC control module.
4. If all circuits test normal, test or replace the appropriate temperature sensor.

Sunload Sensor Circuit Malfunction

1. Ignition OFF, disconnect the harness connector at the sunload sensor.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal C and ground. If greater than the specified range, test the ground circuit for high resistance.
3. Ignition ON, test for 4.8-5.2 volts between the low reference circuit terminal C and the appropriate signal circuit terminal. Left sunload sensor circuit terminal A. Right sunload sensor circuit terminal B. If less than the specified range, test the signal circuit for high resistance. If the circuit tests normal, replace the HVAC control module.
4. If all circuits test normal, test or replace the sunload sensor.

Inside Air Temperature Sensor Circuit Malfunction

1. Ignition OFF, disconnect the harness connector at the inside air temperature sensor.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 2 and ground. If greater than the specified range, test the low reference circuit for high resistance. If the circuit tests normal, replace the HVAC control module.
3. Ignition ON, test for 4.8-5.2 volts between the low reference circuit terminal 2 and the signal circuit terminal 1. If less than the specified range, test the signal circuit for high resistance. If the circuit tests normal, replace the HVAC control module.
4. If all circuits test normal, test or replace the inside air temperature sensor.

1. Test the appropriate air temperature sensor by varying the sensor temperature in water while monitoring the sensor resistance.
2. 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.