Diagnostic Aids

For HVAC system concerns, refer to HVAC Preliminary Checks in Heating, Ventilation, and Air Conditioning.
If condition is intermittent refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
The following table illustrates the A/C compressor relay terminal locations in the underhood fuse block:

DTC P1537 or DTC P1538

A/C Clutch Relay Terminal Identification
B+ - Switch	Ignition 1 Voltage - Coil
Control	A/C Compressor Clutch
Front of Vehicle

2: Listen for a click when the A/C compressor relay operates. When the relay is commanded On with the scan tool, the ECM pulses the relay ON and OFF several times. Repeat the command as necessary.

DTC P1537 or DTC P1538

Step	Action	Yes	No
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1	IMPORTANT: This diagnostic trouble code (DTC) will only set for a failure on the control side of the A/C Compressor Relay. Did you perform the Diagnostic System Check - HVAC?	Go to Step 2	Go to Diagnostic System Check - HVAC Systems - Manual
2	Turn ON the ignition, with the engine OFF. Command the A/C Compressor Relay ON with a scan tool. Does the A/C Relay turn ON and OFF?	Go to Step 3	Go to Step 4
3	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. Did the DTC fail this ignition?	Go to Step 4	Go to Diagnostic Aids
4	Turn OFF the ignition. Disconnect the A/C compressor relay. Turn ON the ignition, with the engine OFF. Probe the ignition 1 voltage circuit of the A/C compressor relay with a test lamp that is connected to a good ground. Does the test lamp illuminate?	Go to Step 5	Go to Step 9
5	Connect a test lamp between the control circuit of the A/C compressor relay and the ignition 1 voltage circuit of the A/C compressor relay. Start the engine. Command the A/C compressor relay ON and OFF with a scan tool. Does the test lamp turn ON and OFF with each command?	Go to Step 10	Go to Step 6
6	Does the test lamp remain illuminated with each command?	Go to Step 8	Go to Step 7
7	Test the A/C compressor relay control circuit for the following: An open A high resistance A short to voltage Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 14	Go to Step 11
8	Test the A/C compressor relay control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 14	Go to Step 11
9	Repair the open or the short to ground in the ignition 1 voltage circuit of the A/C compressor relay. Refer to Wiring Repairs in Wiring Systems. Replace the fuse as necessary. Did you complete the repair?	Go to Step 14	-
10	Test for an intermittent and for a poor connection at the A/C compressor relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 14	Go to Step 12
11	Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 14	Go to Step 13
12	Replace the A/C compressor relay. Did you complete the replacement?	Go to Step 14	-
13	Replace the ECM. Did you complete the replacement?	Go to Step 14	-
14	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. Did the DTC fail this ignition?	Go to Step 2	Go to Step 15
15	Are there any DTCs that have not been diagnosed?	Go to Diagnostic Trouble Code (DTC) List	System OK