Chassis, generic

C0234 Wheel Speed Sensor Frequency Error

Check engine lightUsually off
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

C0234 is publicly unverifiable: the publicly available J2012 tables, NHTSA's bulletins and maker indexes all lack it; in AA1Car's list of GM ABS codes the same wording belongs to C0245. The title describes a speed signal whose frequency is implausible. The control module derives wheel speed from frequency alone: the inductive sensors of the Saab 9-5 with a 29-tooth ring give roughly 70 Hz at 20 km/h, and the Hall sensors of the 9-3 run on a 48-pole ring up to about 2000 Hz. A frequency far off those of the remaining wheels points to a wrong tone ring, a mismatched tyre size or missing teeth. Nisshinbo patented a test that compares every pulse period with a reference at steady speed; a gap of three or five periods marks one or two broken teeth.

Likely causes

Damaged, cracked or wrong tone ring (missing teeth, wrong tooth count)
Tyre or wheel size differs from the other wheels
Excessive air gap or metal debris on the sensor

Symptoms

  • ABS and traction lamps on, sometimes only above a certain speed
  • Unwanted ABS or traction intervention

Repair estimate

DifficultyMediumDIY possible
Parts and labour€40–400
Time0.5–2.5 h

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

Parts involved

wheel speed sensortone ringabs control module

Related codes

C0245C0235C0080

References: aa1car.com, saabwisonline.com, saabwisonline.com, patents.google.com.