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Test Description

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. 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:

  1. 2:  Listen for an audible click when the relay operates. Command the ON and the OFF states. Repeat the commands as necessary.
  2. 12:  The PCM utilizes Electrically Erasable Programmable Read Only Memory (EEPROM). Program the new PCM before you replace the PCM.
DTC P0645

Step Action Yes No
Schematic Reference: HVAC Schematics 
Connector End View Reference: HVAC Connector End Views 
1 Did you perform the HVAC Diagnostic System Check? Go to Step 2  Go to Diagnostic System Check - HVAC Systems - Manual 
2 
  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, command the A/C compressor clutch relay ON and OFF.
Does the clutch relay turn ON and OFF with each command?		 Go to Diagnostic Aids Go to Step 3 
3
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the coil feed circuit of the A/C compressor clutch relay using a test lamp which is connected to a good ground.
Does the test lamp illuminate?		 Go to Step 4  Go to Step 10 
4
  1. Connect a test lamp between the control circuit of the A/C compressor clutch relay and the coil feed circuit of the A/C compressor clutch relay.
  2. With a scan tool, command the A/C compressor clutch relay ON and OFF.
Does the test lamp turn ON and OFF with each command?		 Go to Step 8  Go to Step 5 
5 Does the test lamp remain illuminated with each command? Go to Step 7  Go to Step 6 
6 Test the control circuit of the A/C compressor clutch relay for a short to voltage or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 13  Go to Step 9 
7 Test the control circuit of the A/C compressor clutch relay for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 13  Go to Step 9 
8 Inspect for bad connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 13  Go to Step 11 
9 Inspect for bad connections at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 13  Go to Step 12 
10 Repair the coil feed circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 13  -
11 Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement .
Did you complete the replacement?		 Go to Step 13  -
12 
IMPORTANT: Perform the set up procedure for the PCM.
Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 3.4L.Did you complete the replacement?		 Go to Step 13  -
13
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle according to the Conditions for Running in the DTC, which are specified in the supporting text.
Does the DTC set again?		 Go to Step 2  System OK
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