C0305 code meaning
Inlet Valve Rear Left Performance
What C0305 means
C0305 is missing from the published J2012 lists and is not described by any maker as an ABS valve code. GM does use it: PIP5094 lists the number, and AA1Car's GM table calls it Front Speed Sensor Malfunction, the partner of C0300 in the block before the transfer case motor codes. The title refers to the rear left inlet valve. Besides ABS work, the rear inlet valves carry the electronic brake force split: on the 2011 Saab 9-5 the TRW module lowers rear pressure by cycling the rear valves instead of using a mechanical proportioning valve, and it also uses the valves to hold pressure for hill start assist. A sluggish rear left inlet valve can let that wheel lock early or brake too little, and the module then disables ABS and stability control.
C0305 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C0305
- ABS and brake warning lamps on
- Rear wheel locking early or hill start assist unavailable
Common causes of C0305
- PossibleRear left inlet valve sticking from contaminated fluid
- PossibleValve coil or brake module driver defective
- Less likelyOn GM 4WD trucks, front speed sensor fault in the transfer case system (GM meaning of the number)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Lr ABS inlet valveABS hydraulic blockABS control module
What each part of C0305 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 05 | The exact fault in that area. |
What to do next
- Note C0305 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about C0305
What does C0305 mean?
C0305 means "Inlet Valve Rear Left Performance". C0305 is missing from the published J2012 lists and is not described by any maker as an ABS valve code. It is a generic code, so it means the same on every make.
Is it safe to drive with C0305?
Drive gently and only to a workshop. With C0305 the car can go into limp mode (reduced power) to protect itself.
Will C0305 fail an emissions test?
C0305 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C0305 to fix?
Difficulty: hard. A typical repair takes 1 to 3 hours of work. This is a job for a workshop.
Will C0305 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.