C1223

Symptoms

• ABS warning light on
• traction control and stability control disabled
• possible increased stopping distance and vehicle pulling to one side during braking.

Probable causes

• GM: 1) Defective wheel speed sensor (exposed at the wheel hub; fails from road salt, metallic debris, heat cycling). 2) Damaged wiring/connectors to the sensor (harness flexes with suspension travel). 3) ABS module internal failure (broken solder joints). Toyota/Lexus: 4) Faulty brake light switch - frequently sets C1223 together with C1249 and is a common misdiagnosis
• fix the brake light switch code first. 5) Low system voltage from a weak battery or failing alternator (sources cite voltage dropping below 10.5V triggering C1223, often with C1241).

Diagnostic steps

1. Read chassis codes with a scanner that can access the ABS module (basic engine-only readers cannot see C-codes) and note ALL codes present - companion codes determine the diagnostic path.
2. Toyota/Lexus: if C1249 (brake light switch) or C1241 (low voltage) is present, diagnose those first - test the brake light switch operation and check battery/charging voltage before touching ABS hardware.
3. GM: monitor all four wheel speed sensors in live data while driving slowly in a straight line - all readings must be identical; a sensor reading 0, erratic, or dropping out isolates the faulty corner.
4. Inspect the suspect wheel speed sensor and its wiring for dirt, corrosion, or damage; clean the sensor and tone ring area and repair wiring as needed.
5. Replace the wheel speed sensor (or hub/bearing assembly with integrated sensor) if it produces no signal with wiring verified good.
6. If all sensors read correctly and wiring is good, suspect the ABS module.
7. Clear codes, test drive, and confirm the ABS/traction lights stay off.