Electronic Parking Brake System Malfunction
The C0300 code means the vehicle's onboard diagnostic system has detected: Electronic Parking Brake System Malfunction. This is a critical severity code.
- Keep driving?
- No -- stop driving
- DIY difficulty
- hard
- Estimated cost
- $300 - $800 (parts and labor)
Basic scanners cannot read ABS codes. BlueDriver reads all systems including ABS, SRS, and transmission through your phone.
Check Price on AmazonAffiliate link -- we earn a commission at no extra cost to you.
Basic scanners cannot read ABS codes. This one reads all four systems so you know exactly which sensor failed.
Check Price on AmazonAffiliate link -- we earn a commission at no extra cost to you.
Common Symptoms
- Parking brake warning light on
- Electronic parking brake will not engage
- Electronic parking brake will not release
- Parking brake indicator flashing
Probable Causes (Ranked by Likelihood)
- Failed EPB motor or actuator Very High
- Damaged EPB wiring harness High
- Corroded EPB connector Moderate
- EPB control module failure Low
Step-by-Step Diagnostic Procedure
-
Scan for EPB-specific codes
-
Check EPB motor operation with scan tool
-
Inspect EPB wiring and connectors
-
Test EPB switch input signals
Common Fixes by Vehicle
What techs usually find when diagnosing C0300 on specific vehicles — tap your vehicle for the fix and the exact part:
2007-2018 Chevrolet Silverado/GMC Sierra easy DIY
Rear speed sensor malfunction on GM trucks usually points to the vehicle speed sensor (VSS) on the transfer case (4WD) or transmission tail shaft (2WD). The sensor is easy to access from underneath. Unplug the connector, remove the single bolt, pull the sensor out, and install the new one. Check the drive gear inside the housing for stripped teeth while the sensor is out.
Labor: 20-30 min2004-2018 Ford F-150/F-250 easy DIY
On Ford trucks, C0300 often refers to the rear differential speed sensor. The sensor is threaded into the rear differential housing. Road salt and debris corrode it in place. Use penetrating oil and a deep-well socket to remove it. If the sensor breaks off, the diff cover must come off to extract it. Apply anti-seize to the new sensor threads to prevent future removal issues.
Labor: 30-45 min2008-2017 Chevrolet Equinox/GMC Terrain easy DIY
The rear speed sensor on AWD Equinox/Terrain is part of the rear differential assembly. If just the sensor has failed, it can be replaced individually. If the code persists after sensor replacement, check the reluctor ring for damaged teeth. On FWD models, the rear wheel hub speed sensors serve as rear speed inputs -- replace the hub assembly if faulty.
Labor: 30 min - 1 hourFrequently Asked Questions
What does code C0300 mean?
C0300 indicates a fault with the electronic parking brake system malfunction system in your vehicle.
Can I drive with C0300?
Do not drive. Have the vehicle towed to a repair shop.
How much does it cost to fix C0300?
Typical repair costs are $300 - $800 (parts and labor).
Sources
This page is built from documented references. Verify against your own service info before repair work.
See All Codes & Fixes for Your Vehicle
Explore More
Was this helpful?
Share carcodefinder.com with a friend who needs to decode their check engine light.