ASE G1 Auto Maintenance and Light RepairBrakesHard
A vehicle with an electronic parking brake (EPB) cannot be released. The dashboard warning light for the EPB is illuminated. A technician connects a scan tool and finds no Diagnostic Trouble Codes (DTCs). Which of the following is the MOST likely cause of this issue?
- AA mechanical seizure within the caliper mechanism.
- BA low battery voltage preventing EPB motor operation.
- CAn open circuit in a wheel speed sensor.
- DA faulty EPB control module requiring replacement.
Show answer & explanationAnswer & explanation
Correct answer: B. A low battery voltage preventing EPB motor operation.
Electronic parking brake systems are highly sensitive to battery voltage. If the battery voltage is too low, the EPB control module may not have enough power to actuate the parking brake motors, resulting in a 'stuck' brake and an illuminated warning light, even without setting a specific DTC for the EPB module itself, as it might just be a power issue.
Why the other options are wrong
- A. A mechanical seizure within the caliper mechanism would likely prevent the brake from releasing, but without a DTC, it's less likely to be the primary cause of an *electrical* warning light, and a scan tool might reveal motor current draw issues or position sensor faults.
- C. An open circuit in a wheel speed sensor would typically set an ABS/TCS related DTC (e.g., C0200) and might affect ABS operation, but it's not directly responsible for an EPB not releasing without any EPB-specific DTCs.
- D. A faulty EPB control module would typically set a specific DTC, especially if it's completely non-responsive.
EPB Low Voltage
Electronic Parking Brake systems are sensitive to low battery voltage, which can prevent operation and illumination of a warning light without setting a specific diagnostic trouble code.
- EPB motors require sufficient power
- Low voltage inhibits release/apply
- Can occur without a dedicated DTC
Memory trick: No code, no release? Check the battery, for power's the lease!