Chassis, generic

C0305 Inlet Valve Rear Left Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Rear left inlet valve sticking from contaminated fluid
Valve coil or brake module driver defective
On GM 4WD trucks, front speed sensor fault in the transfer case system (GM meaning of the number)

Symptoms

  • ABS and brake warning lamps on
  • Rear wheel locking early or hill start assist unavailable

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–1,500
Time1–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

lr abs inlet valveabs hydraulic blockabs control module

Related codes

C0307C0300

References: static.nhtsa.gov, aa1car.com, saabwisonline.com, saabwisonline.com.