Service Information

Spark

DTC P0537 or P0538

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 Descriptors

DTC P0537: Air Conditioning (A/C) Evaporator Temperature Sensor Circuit Low Voltage

DTC P0538: Air Conditioning (A/C) Evaporator Temperature Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Signal	P0537	P0538	P0538*	--
Low Reference	--	P0538	P0538*	--
* Internal ECM or sensor damage may occur if the circuit is shorted to B+.

Typical Scan Tool Data

A/C Evaporator Temp. Sensor (Without FX3)

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: Engine running in Closed Loop, A/C off. Parameter Normal Range: Varies with ambient temperature
Signal	142.5°C (288.5°F)	-48°C (-54.4°F)	-48°C (-54.4°F)*
Low Reference	--	-48°C (-54.4°F)	-48°C (-54.4°F)*
* Internal ECM or sensor damage may occur if the circuit is shorted to B+.

A/C Evaporator Temp. Sensor (FX3)

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: Engine running in Closed Loop, A/C off. Parameter Normal Range: Varies with ambient temperature
Signal	215°C (419°F)	-40°C (-40°F)	-40°C (-40°F)
Low Reference	--	-40°C (-40°F)	-40°C (-40°F)
* Internal ECM or sensor damage may occur if the circuit is shorted to B+.

When the refrigerant temperature of the evaporator drops below certain temperature, the evaporator cores get blocked with frost or ice, reducing the airflow, lowering the cooling capacity. The thermistor is a sensor which is used to prevent frosting or icing. The thermistor is installed on the evaporator.

Conditions for Running the DTC

P0537 or P0538 (Without FX3)

•	The engine coolant temperature is greater than 60°C (140°F).

•	The DTC runs continuously when the above conditions are met.

P0537 or P0538 (FX3)

•	DTC P0562 or P0563 is not set.

•	The engine is running for greater than 10s.

•	The DTC runs continuously when the above conditions are met.

Conditions for Setting the DTC

P0537 (Without FX3)

The ECM detects that the A/C evaporator temperature sensor signal voltage is less than 0.0293V.

P0538 (Without FX3)

The ECM detects that the A/C evaporator temperature sensor signal voltage is greater than 4.9022V.

P0537 (FX3)

The ECM detects that the A/C evaporator temperature sensor signal voltage is less than 0.1V.

P0538 (FX3)

The ECM detects that A/C evaporator temperature sensor signal voltage is greater than 4.9V.

Action Taken When the DTC Sets

DTC P0537 and P0538 are Type C DTCs.

Conditions for Clearing the DTC

DTC P0537 and P0538 are Type C DTCs.

Reference Information

Schematic Reference

•	HVAC Schematics for the automatic system

•	HVAC Schematics for the manual system

Connector End View Reference

Component Connector End Views

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Engine running, verify that the DTC P0537 or P0538 is not set.

⇒	If any of the DTCs are set, perform Circuit/System Testing.

Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

Ignition OFF, disconnect the harness connector at the B39 A/C Evaporator Temperature Sensor.
Ignition OFF, test for less than 5 Ω 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 K20 ECM.

Ignition ON, verify the scan tool A/C evaporator temperature sensor parameter is less than below value.

•	-47°C (-52.6°F) (Without FX3)

•	-39°C (-38.2°F) (FX3)

⇒	If greater than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.

Note: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.

Connect a 1A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the scan tool A/C evaporator temperature sensor parameter is greater than below value.

•	141.5°C (286.7°F) (Without FX3)

•	214°C (417.2°F) (With FX3)

⇒	If less than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.

If all circuits test normal, test or replace the B39 A/C Evaporator Temperature Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Evaporator Air Temperature Sensor Replacement

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