Powertrain, generic · Transmission

P0857 Traction Control Input Signal Range/Performance

Check engine lightUsually off

EmissionsNot relevant

Drive cycleNot required

Limp modeNo

The traction control input carries the request of the ABS/stability module to the engine module to cut torque when wheels spin. Older cars used a wire with a voltage or duty-cycle signal, hence the low and high variants; today it is a CAN message, where pure loss of communication sets U0121 or U0415 instead. California's OBD rule counts traction control as a safety-only system that may be exempted, so these codes normally carry no MIL. P0857 means the signal is electrically valid but does not fit the driving state, such as a request without wheel slip or switching too often. No maker documents the code; GM covers such checks under P0856. The receiving module ignores the request and traction control is disabled.

Likely causes

Software or calibration of brake or engine module

Loose contact or corrosion between brake module and engine module

Wheel speed fault in the ABS causing false slip detection

Brake module faulty

Symptoms

Traction or stability control lamp on, system switched off
Traction control intervenes unexpectedly or not at all
Engine power briefly reduced

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€80–1,200

Time0.5–3 h

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

Parts involved

abs control moduleengine control moduleserial data linesensor wiring

Related codes

P0856 P0858 P0859 U0121 U0415

References: law.cornell.edu, gsi.ext.gm.com, saabwisonline.com.