Test Description

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

4: This step tests for the proper operation of the circuit in the high voltage range.
5: This step tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens upon performing this test, the signal circuit has a short to voltage.

DTC P0537 or P0538

Step	Action	Values	Yes	No
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Turn OFF the ignition. Disconnect the evaporator temperature sensor. Refer to Evaporator Core Replacement Test for resistance between the low reference circuit terminal and ground. With a Digital Multi Meter DMM, observe the Evaporator Temp resistance parameter. Is the Evaporator Temp parameter greater than the specified value?	1.0 Ω	Go to Step 8	Go to Step 3
3	Install a DMM. Turn ON the ignition, with the engine OFF. With a DMM, observe the Evaporator Temp signal circuit voltage parameter. Does the DMM indicate that the Evaporator Temp signal voltage parameter is within the specified value range?	0.443-4.55 V	Go to Testing for Intermittent Conditions and Poor Connections	Go to Step 4
4	Turn OFF the ignition. Disconnect the evaporator temp sensor. Turn ON the ignition, with the engine OFF. With a DMM, observe the evaporator temp signal voltage parameter at the male connection in the engine compartment. Refer to Evaporator Core Replacement Is the Evaporator Temp signal voltage parameter greater than the specified value?	4.55 V	Go to Step 5	Go to Step 6
5	Turn OFF the ignition. Connect a 3-amp fused jumper wire between the signal circuit of the evaporator temperature sensor and the low reference circuit of the evaporator temperature sensor. Turn ON the ignition, with the engine OFF. With a DMM, observe the Evaporator Temp voltage parameter. Is the Evaporator Temp voltage parameter less than the specified value?	0.443 V	Go to Step 9	Go to Step 7
6	Test the signal circuit of the evaporator temperature sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	-	Go to Step 13	Go to Step 10
7	Test the signal circuit of the evaporator temperature sensor for one of the following conditions: A short to voltage A high resistance An open Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	-	Go to Step 13	Go to Step 8
8	Test the low reference circuit of the evaporator temperature sensor for one of the following conditions: A high resistance An open Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	-	Go to Step 13	Go to Step 9
9	Inspect for poor connections at the harness connector of the evaporator temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?	-	Go to Step 13	Go to Step 11
10	Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?	-	Go to Step 13	Go to Step 12
11	Replace the evaporator temperature sensor. Refer to Evaporator Core Replacement . Did you complete the replacement?	-	Go to Step 13	-
12	Replace the HVAC control module. Refer to Control Module References for HVAC control module replacement, setup, and programming. Did you complete the replacement?	-	Go to Step 13	-
13	Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC. Does the DTC reset?	-	Go to Step 2	System OK