Pinpoint Test B: DTC P0537 or DTC P0538
Climate Control System
Pinpoint Tests
Pinpoint Test B: DTC P0537 or DTC P0538
Refer to Wiring Diagram Set 23, Electronic Engine Controls - 2.3L for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 54, Manual Climate Control System for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, the evaporator discharge air temperature sensor receives a ground from the PCM through circuit RE407 (YE/VT). A 5-volt reference voltage is supplied to the evaporator discharge air temperature sensor from the PCM through circuit VH406 (VT/BN).
- DTC P0537 A/C Evaporator Temperature Sensor Low - The module senses excessive voltage drop on the sensor reference voltage circuit, indicating a short directly to ground.
- DTC P0538 A/C Evaporator Temperature Sensor High - The module senses no voltage drop on the sensor reference voltage circuit, indicating an open circuit.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Evaporator discharge air temperature sensor
- PCM
PINPOINT TEST B: DTC P0537 OR DTC P0538
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B1 CHECK THE SENSOR RESISTANCE
- Ignition OFF.
- Disconnect: Evaporator Discharge Temperature Sensor C2295.
- Carry out the evaporator discharge temperature sensor component test. Evaporator Discharge Air Temperature Sensor
- Is the resistance within the specified values for the temperatures?
Yes
GO to B2.
No
INSTALL a new evaporator discharge air temperature sensor. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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B2 CHECK THE HVAC MODULE OUTPUT VOLTAGE
- Ignition ON.
- Press the AUTO button.
- Measure the voltage between evaporator discharge air temperature sensor C2295-2, circuit VH406 (VT/BN), harness side and C2295-1, circuit RE407 (YE/VT), harness side.
- Is the voltage between 4.7 and 5.1 volts?
Yes
INSTALL a new evaporator discharge air temperature sensor. If code returns, GO to B7.
No
If diagnosing DTC P0538, GO to B3.
If diagnosing DTC P0537, GO to B5.
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B3 CHECK CIRCUIT VH406 (VT/BN) FOR AN OPEN
- Ignition OFF.
- Disconnect: PCM C175b.
- Measure the resistance between PCM C175b-53, circuit VH406 (VT/BN), harness side and evaporator discharge air temperature sensor C2295-2, circuit VH406 (VT/BN), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to B4.
No
REPAIR circuit VH406 (VT/BN) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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B4 CHECK CIRCUIT RE407 (YE/VT) FOR AN OPEN
- Measure the resistance between PCM C175b-58, circuit RE407 (YE/VT), harness side and evaporator discharge air temperature sensor C2295-1, circuit RE407 (YE/VT), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to B7.
No
REPAIR circuit RE407 (YE/VT) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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B5 CHECK CIRCUITS VH406 (VT/BN) AND RE407 (YE/VT) FOR A SHORT TOGETHER
- Ignition OFF.
- Disconnect: PCM C175b.
- Measure the resistance between evaporator discharge air temperature sensor C2295-2, circuit VH406 (VT/BN), harness side and C2295-1, circuit RE407 (YE/VT), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to B6.
No
REPAIR circuits VH406 (VT/BN) and RE407 (YE/VT) for a short together. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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B6 CHECK CIRCUIT VH406 (VT/BN) FOR A SHORT TO GROUND
- Measure the resistance between PCM C175b-53, circuit VH406 (VT/BN), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to B7.
No
REPAIR circuit VH406 (VT/BN) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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B7 CHECK THE PCM CONNECTION
- Clear the DTCs.
- Disconnect all the PCM connectors.
- Check for:
- corrosion.
- pushed-out pins.
- incorrectly seated connector.
- Connect and correctly seat all the PCM connectors.
- Operate the system.
- Does the concern return?
Yes
INSTALL a new PCM. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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