Rear Speed Sensor Malfunction (GM)
The C0300 code means the vehicle's onboard diagnostic system has detected: Rear Speed Sensor Malfunction (GM). This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $100 - $500 (diagnose before parts)
Basic scanners cannot read ABS codes. BlueDriver reads all systems including ABS, SRS, and transmission through your phone.
Basic scanners cannot read ABS codes. This one reads all four systems so you know exactly which sensor failed.
Affiliate links — we earn a commission at no extra cost to you.
Common Symptoms
- Warning light on
- Behavior of the affected chassis system degraded
Probable Causes (Ranked by Likelihood)
- Fault in the chassis control component this code names (Rear Speed Sensor Malfunction) High
- Damaged wiring or a corroded connector in that circuit - road-splash zones corrode connectors High
- Failed related sensor or actuator Moderate
- Control module fault Low
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 C0300 mean?
C0300 is a chassis code used primarily by GM vehicles: Rear Speed Sensor Malfunction. It concerns the chassis control system.
Can I keep driving with C0300?
Generally yes; the chassis control system may be degraded. Diagnose soon, and treat any brake- or steering-related behavior change as urgent.
Is C0300 the same on every make?
The decimal C0xxx range is dominated by GM's assignments (Chevrolet, GMC, Buick, Cadillac). Other makes may use this ID differently - if your vehicle is not a GM product, verify the meaning in your make's service information.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Read the code with a GM-capable scan tool and note the symptom byte/subcode if shown.
-
View live data for the named circuit (e.g. all four wheel speeds while rolling for wheel-speed codes).
-
Inspect the circuit's wiring and connectors - chassis harnesses live in the splash zone and corrode first.
-
Follow the GM pinpoint test for C0300 before replacing components.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
Commonly Affected Vehicles
- Chevrolet, GMC, Buick, Cadillac (GM chassis code range)
Related Codes
See All Codes & Fixes for Your Vehicle
Explore More
Was this helpful?
Send this to whoever is fixing the car — your mechanic, or the person asking what the light means.