ABS Valve Relay Circuit Short to Ground
What does C0123 mean?
The C0123 code means the vehicle's onboard diagnostic system has detected: ABS Valve Relay Circuit Short to Ground. This is a critical severity code.
Common Symptoms
- ABS warning light on
- ABS fuse may blow
- No ABS activation during braking
- Traction control light illuminated
- Clicking from relay area at startup
Probable Causes (Ranked by Likelihood)
- Short to ground in ABS valve relay wiring Very High
- Water damage to relay connector or socket High
- Damaged relay coil shorted internally to ground Moderate
- Chafed wiring touching vehicle body or frame Moderate
- ABS control module ground-side driver failure Low
Step-by-Step Diagnostic Procedure
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Check ABS-related fuses for blown condition
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Remove relay and measure resistance from control terminal to ground -- should be infinite
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Inspect wiring harness for chafing or bare wires touching ground
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Look for water intrusion or corrosion in the relay socket area
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Test a new relay and monitor for the code returning
Frequently Asked Questions
What is the difference between C0122 and C0123?
C0122 indicates a short to battery voltage (positive), while C0123 indicates a short to ground (negative). Both prevent proper relay operation but require tracing different parts of the circuit to find the fault.
Can corrosion cause a short to ground?
Yes. Corrosion creates conductive paths between the wire and vehicle body. Salt-belt vehicles are particularly susceptible to corrosion-related shorts in underhood and underbody wiring.
Should I replace the entire ABS module for this code?
Not necessarily. Start with the relay and wiring. Only replace the ABS module if the short is traced to an internal module failure, which is uncommon. Most C0123 faults are caused by wiring or relay issues.