GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Optra 🢒 Engine 🢒 Engine Controls - 1.6L (L91) 🢒 DTC P1537 or P1538

Circuit Description

The air conditioning (A/C) compressor relay is controlled by the engine control module (ECM). Ignition 1 voltage is supplied directly to the A/C compressor relay. The ECM controls the relay by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the ECM. When the ECM is commanding a component ON, the voltage of the control circuit should be near 0 volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses a voltage other than what is expected, a DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTCs:

    • DTC P1537 Air Conditioning (A/C) Clutch Relay Control Circuit High Voltage
    • DTC P1538 Air Conditioning (A/C) Clutch Relay Control Circuit Low Voltage

Conditions for Running the DTC
    • The engine is running.
    • The ignition 1 voltage is more than 11.0 volts.
    • The A/C is requested ON.
    • The A/C compressor is running (P1537 only)
    • The DTC runs continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM detects a low voltage on the A/C clutch relay control circuit for more than 25 seconds.

OR

The ECM detects a high voltage on the A/C clutch relay control circuit for more than 25 seconds.

Action Taken When the DTC Sets
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The ECM will store conditions which were present when the DTC was set as Failure Records data only.
    • This information will not be stored in the Freeze Frame data.

Conditions for Clearing the MIL/DTC
    • DTCs can be cleared by using the scan tool.
    • Disconnect the ECM battery feed for more than 10 seconds.

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:

A/C Clutch Relay Terminal Identification

B+ - Switch

Ignition 1 Voltage - Coil

Control

A/C Compressor Clutch

Front of Vehicle

  1. 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.

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

  1. Turn ON the ignition, with the engine OFF.
  2. 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
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. 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

  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor relay.
  3. Turn ON the ignition, with the engine OFF.
  4. 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

  1. 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.
  2. Start the engine.
  3. 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
  1. 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.
  2. 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. Refer to Engine Control Module Replacement.

Did you complete the replacement?

Go to Step 14

--

14
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. 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