Park Brake System Check Process
Notice: The amount of time it takes for the parking brake to release will vary based on the temperature and battery voltage. In extremely cold weather, it can take up to 15 seconds to release the parking brake. This is normal system operation.
Notice: Use care when probing terminals to measure voltage and resistance values. The Digital Multimeter (DMM) probe can damage the connector terminal and cause a poor connection. A damaged terminal condition is very hard to diagnose.
Before beginning diagnosis on the electric/auto park brake system, you need a detailed description from the owner of when the concern occurred. This information can be useful in duplicating the condition. Always begin diagnosis with a visual inspection of all of the following:
| • | The connectors |
| • | The wiring |
| • | The wire routing |
| • | The wire retention |
Many times one of the following considerations is the cause of a malfunction:
| • | A disconnected or loose connector |
| • | A blown fuse |
| • | An open circuit breaker |
| • | A corroded terminal |
| • | A misrouted wire |
Refer to Electric/Auto Park System Description or Electric/Auto Park System Operation for a description and the operation of the Electric/Auto Parking Brake.
Park Brake System Check Light Flashes ON Frequently
Checks | Action |
|---|---|
DEFINITION: The AUTO PARK light flashes frequently while driving. | |
The AUTO PARK light will come on while driving. The interval should be greater than 15 minutes. | Intervals less than 15 minutes indicate a system problem. This indicates a leak or other failure which could lead to an inability to release the park brake. Check for any sign of an external leak. If there is none, the problem is internal. Refer to . As the problem continues, the intervals will become shorter leading to constant pump operation. |
The system leaks fluid. | Check the reservoir fill level and look for leak-fluid spillage. Refer to Checking and Adding Park Brake Fluid . |
There is a leakdown in the solenoid valve. | Replace the solenoid valve. Refer to Park Brake Solenoid Valve Replacement . |
The pump switch is defective. | Check the pressure cycles. The pressure differential between apply and release should be approximately 350 psi (2413.25 kPa). |
Park Brake System Check Light Stays On All the Time
Checks | Action | ||||||||
|---|---|---|---|---|---|---|---|---|---|
DEFINITION: The AUTO PARK light stays on all the time, even when the parking brake is released. | |||||||||
Confirm that the parking brake is fully released. | Turn the rear wheels and check for drag. | ||||||||
Check the light circuit for a short. | Repair and/or replace the light circuit. | ||||||||
The pump runs constantly. |
| ||||||||
Park Brake System Check Light On
Checks | Action |
|---|---|
DEFINITION: The AUTO PARK light is on and the parking brake will not release. | |
The pump is burned out. | Replace the pump. Refer to Park Brake Pump Replacement . |
The relay is failed open. | Replace the relay. Refer to Park Brake Pressure Relay Replacement . |
The solenoid valve is failed open. | Replace the solenoid valve. Refer to Park Brake Solenoid Valve Replacement . |
