GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2009 🢒 Montana SV6 Ext. 🢒 DTC 🢒 DTC 021 or 022

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 Descriptor

DTC 021: Compressor Relay Circuit Short to Ground

DTC 022: Level Control Compressor Relay Circuit Short to Battery or Open

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Relay Coil B+

1

1

--

--

Relay Switch B+

--

1

--

--

Relay Coil Control

021

023

022

022

--

Relay Controlled Output

2

--

3

--

1. Automatic Level Control (ALC) Compressor Relay Inoperative

2. Automatic Level Control (ALC) Sensor Relay Control Inoperative

3. Automatic Level Control (ALC) Sensor Relay Control Always ON

Circuit/System Description

The automatic level control sensor monitors the compressor relay coil circuitry for a short to ground, open, or short to voltage.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The DTC is set when the automatic level control sensor detects the compressor relay coil control circuit is shorted to ground, open, or shorted to voltage.

Action Taken When the DTC Sets
    • The automatic level control sensor disables the compressor.
    • The automatic level control sensor disables the inflator functions.
    • Lowering functions shall continue.

Conditions for Clearing the DTC

021

The conditions that caused the DTC have been removed.

022

    • The conditions that caused the DTC have been removed.
    • The ignition has transitioned from OFF to ON.

Diagnostic Aids

021

    • Compressor motor will run continuously.
    • When this occurs, DTC 023 will be set.

022

A short to battery or an open circuit in the level control compressor relay control circuit will set this DTC.

Reference Information

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Level Control Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing
  1. Ignition OFF, disconnect the automatic level control compressor relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
    3. ⇒If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.
    4. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the automatic level control compressor relay.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
    5. ⇒If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  5. Disconnect the harness connector at the automatic level control sensor.
  6. Test for less than 5.0 ohm between the ground circuit terminal A and ground.
    7. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the automatic level control sensor.
  8. Connect a 3A fused jumper wire between the B+ circuit relay terminal 30 and the relay control circuit terminal 87. Verify the automatic level control sensor is activated.
    9. ⇒If the automatic level control sensor does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the automatic level control sensor.
  9. Connect a test lamp between the relay B+ circuit terminal 86 and the relay control circuit terminal 85.
  10. Press the automatic level control switch ON and OFF. The test lamp should turn ON and OFF when changing between the commanded states.
    11. ⇒If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the automatic level control sensor.
    ⇒If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the automatic level control sensor.
  11. If all circuits test normal, test or replace the automatic level control sensor.

Component Testing

Relay Test

  1. Ignition OFF, disconnect the automatic level control compressor relay.
  2. Test for 0-2 ohms between terminals 85 and 86.
    3. ⇒If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals:
    4. • 30 and 86
    • 30 and 87
    • 30 and 85
    • 85 and 87
    ⇒If not the specified value, replace the relay.
  4. Install a 3A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.
    5. ⇒If greater than the specified range, replace the relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Important: System untested codes will continue to flash until self test has been completed after automatic level control sensor replacement.

    •  Automatic Level Control Relay Replacement
    •  Control Module References for automatic level control sensor replacement, setup, and programming