C0301: Air Suspension Compressor Relay
The air suspension control module has detected a fault in the compressor relay circuit. The compressor cannot be energized which prevents the system from refilling the air struts and ride height drops over time.
What C0301 means
C0301 is a generic OBD-II chassis code in the tires & suspension group.
- Check engine light
- Usually off
- Emissions-related
- No
- Limp mode possible
- Not typical
- Drive cycle to clear
- Not required
Get it fixed
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Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Common causes
- 01Compressor relay failedMost likely
- 02Relay wiring or fuse faultPossible
- 03Internal module faultLess likely
Can I drive with C0301?
Usually yes, for a short time.
The car will often drive normally, but get it diagnosed soon. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
Why we rate it moderate
- Usually lights the ABS, traction or stability warning instead of the check engine light
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose C0301
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just C0301. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Fix other faults first
If other codes are stored, start with power-supply, sensor-circuit and communication codes. They can cause this code as a side effect.
- 3
Check live data
Watch the related sensor and actuator readings in live data (Compressor relay, Air compressor, Air suspension module) and compare them with expected values in the service information for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Compressor relay failed; relay wiring or fuse fault; internal module fault. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and drive the car under the conditions in the freeze-frame data to confirm it does not return.
C0301 repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Moderate
- Good DIY job?
- Yes, with a scan tool
Needs a scan tool and some experience with testing.
Parts and systems involved
- Compressor relay
- Air compressor
- Air suspension module
C0301 FAQ
What does C0301 mean?
C0301 means “Air Suspension Compressor Relay”. The air suspension control module has detected a fault in the compressor relay circuit. The compressor cannot be energized which prevents the system from refilling the air struts and ride height drops over time.
Is C0301 serious? Can I keep driving?
We rate C0301 as moderate severity. Usually yes, for a short time. The car will often drive normally, but get it diagnosed soon. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
What causes C0301?
The most common causes, from most to least likely: Compressor relay failed; Relay wiring or fuse fault; Internal module fault. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix C0301?
Typical labor is about $40–$250 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix C0301 myself?
DIY difficulty is moderate. Many owners can handle it with a scan tool, a multimeter and basic hand tools. Always confirm the cause before buying parts.
Will C0301 clear itself?
If the fault was intermittent, the warning may go off once the computer stops seeing it, but the code stays in memory. Fix the cause; clearing the code alone doesn’t repair anything.