Front Speed Sensor Malfunction (GM)
The C0305 code means the vehicle's onboard diagnostic system has detected: Front 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)
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Basic scanners cannot read ABS codes. This one reads all four systems so you know exactly which sensor failed.
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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 (Front 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
Frequently Asked Questions
What does C0305 mean?
C0305 is a chassis code used primarily by GM vehicles: Front Speed Sensor Malfunction. It concerns the chassis control system.
Can I keep driving with C0305?
Generally yes; the chassis control system may be degraded. Diagnose soon, and treat any brake- or steering-related behavior change as urgent.
Is C0305 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 C0305 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
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