Code 38/41/42 - ESB Will Not Hold Motor: Notes

• Code 38 - Left Front ESB
• Code 41 - Right Front ESB
• Code 42 - Rear ESB

Detects slippage in left front, right front or rear Expansion Spring Brake (ESB). During initialization and braking, motor is rehomed (ESB piston is moved to its highest position and check valve lifted off its seat). If ESB slips, motor/piston will move. During next key-on initialization, a rehome of motor verifies motor/piston remained at home (highest) position. If motor movement is detected, ESB is slipping.

If ESB cannot hold home position, piston may be pushed back when brake pedal is applied, causing brake pedal to drop.

Codes 38/41/42 can set during initialization and EBCM detects that ESB could not hold piston in home position. Code 86 is always set with Codes 38/41/42. Code will be stored, ABS will be disabled and ABS and BRAKE warning lights will be illuminated.

Fig 1: Code 38/41/42 Diagnostic Flow Chart

Courtesy of GENERAL MOTORS CORP.

1. Checks for a broken or defective ESB. This causes left front, right front or rear piston to be back driven by hydraulic pressure, resulting in pedal movement.
2. Ensures proper motor circuits are located in proper connector cavities.
3. Checks for high resistance in motor high circuit.
4. Checks for high resistance in motor low circuit.
5. Checks for proper resistance of motor windings.
6. Checks terminals and connectors for corrosion and contact.
7. Checks for malfunctioning EBCM.