GM Service Manual Online
For 1990-2009 cars only

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 Descriptors

DTC C0625 08: Left Rear Position Sensor Circuit Signal Invalid

DTC C0625 55: Left Rear Position Sensor Circuit Expected Number of Transitions/Events not Reached

DTC C0630 08: Right Rear Position Sensor Circuit Signal Invalid

DTC C0630 55: Right Rear Position Sensor Circuit Expected Number of Transitions/Events not Reached

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Left Rear Air Suspension Sensor 5-Volt Voltage Reference

C0696 00

C0625 08

C0696 00

--

Left Rear Air Suspension Sensor Signal

C0625 08

C0625 08

C0625 08

C0625 55

Left Rear Air Suspension Sensor Low Reference

--

C0625 08

--

--

Right Rear Air Suspension Sensor 5-Volt Voltage Reference

C0696 00

C0630 08

C0696 00

--

Right Rear Air Suspension Sensor Signal

C0630 08

C0630 08

C0630 08

C0630 55

Right Rear Air Suspension Sensor Low Reference

--

C0630 08

--

--

Circuit/System Description

The left and right rear air suspension position sensors provide a signal voltage between 0.25-4.75 volts to the air suspension control module. This signal voltage represents the wheel's position relative to the body. The air suspension control module provides a 5-volt reference and a low reference to the sensors.

Conditions for Running the DTC

    • Ignition voltage is between 9-16 volts.
    • Vehicle is in motion.

Conditions for Setting the DTC

    • The air suspension module detects the voltage at the air suspension sensor signal circuit is less than 0.25 volt or greater than 4.75 volts for more than 500 milliseconds.
    • The air suspension module detects that there is a wide differential between the signal voltage ranges of one sensor in comparison to the other over a predetermined period of time.

Action Taken When the DTC Sets

    • Air suspension functionality is suspended.
    • The SERVICE SUSPENSION SYSTEM message is displayed.

Conditions for Clearing the DTC

The condition for setting the DTC no longer exists.

Reference Information

Schematic Reference

Air Suspension Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Air Suspension 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, remove the ECAS Fuse in the underhood fuse block and disconnect the harness connector at the appropriate position sensor.
  2. Test for less than 2.0 ohms between low reference circuit terminal 3 (LR) or terminal 1 (RR) and ground.
  3. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the air suspension control module.
  4. Install the ECAS Fuse in the underhood fuse block.
  5. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 1 (LR) or terminal 3 (RR) and ground.
  6. If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the air suspension control module.
    If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the air suspension control module.
  7. Verify the appropriate scan tool Position Sensor parameter is less than 0.25 volts.
  8. If greater than the specified range, test the signal circuit terminal 2 for a short to voltage. If the circuit tests normal, replace the air suspension control module.
  9. Install a 3A fused jumper wire between the signal circuit terminal 2 and the 5-volt reference circuit terminal 1 (LR) or terminal 3 (RR). Verify the appropriate scan tool Position Sensor parameter is greater than 4.8 volts.
  10. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the air suspension control module.
  11. If all circuits test normal, test or replace the appropriate air suspension sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Air Spring Leveling Sensor Replacement
    •  Suspension Position Calibration
    •  Control Module References for air suspension control module replacement, setup, and programming