Chassis, generic

C0001 TCS Control Channel A Valve 1

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C0001 concerns the first traction control valve of hydraulic channel A, usually one of the two brake circuits in the ABS/ESC modulator. To brake a spinning drive wheel without driver input, a TCS-capable modulator carries an extra isolation valve and priming valve per circuit: the normally open isolation valve closes off the master cylinder, while the normally closed priming valve opens so the pump can draw fluid and build pressure. Which of the two a maker numbers as valve 1 is not published. The module watches the coil circuit and whether pressure follows the command; a fault switches off traction and usually stability control and lights the warning lamp, while ordinary braking remains. No manufacturer documents this code publicly.

Likely causes

Solenoid coil open or shorted
Corroded or chafed wiring to the modulator
Internal hydraulic modulator fault

Symptoms

  • ABS warning lamp on
  • Traction and stability control disabled
  • Normal braking retained without ABS

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€300–1,600
Time1.5–4 h

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

Parts involved

tcs valve a1

Related codes

C0002C0003C0004

References: rosap.ntl.bts.gov, patents.google.com, en.wikipedia.org.