ABS Warning Light Circuit Short to Battery
Diagnostic trouble code C1220 indicates a short to battery voltage (B+) in the ABS warning lamp output circuit. The ABS control module has detected that the voltage on the lamp circuit remains high when it should be off, meaning the wiring is making contact with a constant voltage source. In Toyota and Lexus vehicles, this code is specifically linked to the instrument panel lighting control managed by the ABS or Vehicle Stability Control (VSC) module.
1. Commonly Affected Makes
2. Most Common Causes
- ABS lamp circuit wiring shorted to battery power (B+)
- Faulty ABS relay or control module with internal lamp driver failure
- ABS warning lamp bulb with internal short circuit
- Damaged connector or harness with pins contacting chassis or voltage source
- Faulty instrument cluster (combination meter)
3. Symptoms You Will Notice
- ABS warning light stays on continuously
- ABS warning light may be dim or flicker
- ABS system may be disabled or inoperative
4. Step-by-Step Diagnosis
Check for technical service bulletins (TSBs) related to C1220 for the specific vehicle model.
Visually inspect the ABS warning lamp circuit wiring for damage, chafing, or contact with power sources.
Test the ABS warning lamp circuit for voltage with the ignition on and lamp off; voltage should be near 0V.
Check the ABS module connector for bent, corroded, or shorted pins.
If wiring and connectors are okay, suspect a faulty ABS module or instrument cluster.
5. Frequently Asked Questions
Is it safe to drive?▼
Driving is generally safe, but the ABS system may be disabled, increasing stopping distances on slippery surfaces. Have it diagnosed soon.
How much does it cost to fix?▼
Repair costs range from $100 to $500, depending on whether it's a simple wiring repair or module replacement.