C0400Traction Control Solenoid Valve Circuit
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- C0400 is publicly undocumented: none of the published J2012 lists contains it, neither does GM's PIP5094, and a search of NHTSA's bulletin index finds nothing. Only the part from the title is described here. For traction control the brake unit must build pressure without the driver pressing the pedal. In the TC/ABS unit of the 2004 Saab 9-5 one pressure build valve and one pressure release valve per front wheel are used only in TCS mode, while the return pump supplies fluid; Bosch likewise places all control valves and the pump in one hydraulic unit. Each time the ignition comes on, the Saab module tests each valve with a 20 ms pulse; if one fails it switches off ESP, TCS and ABS and lights ABS, brake and ESP OFF lamps.
- What you may notice
- ABS, traction control and stability warning lamps on
- Wheels spin freely when pulling away on slippery ground
- Likely causes
- PossibleOpen or shorted coil of a traction control valve
- PossibleValve driver inside the brake control module failed
- RarePoor supply or ground of the brake control module
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €150 – €1,800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.