What Does C1204 Mean?
The ABS module has detected a short-to-battery-voltage condition on the rear outlet valve solenoid coil circuit. Unwanted voltage on this circuit prevents proper ABS modulation of rear brake pressure. The ABS system is disabled and the dashboard ABS warning lamp is illuminated. Standard braking continues to work normally.
Common Causes
40%
Wiring harness chafed or melted against a nearby B+ power feed wire, creating a short to voltage on the rear outlet valve circuit
25%
Internal short to voltage within the rear outlet valve solenoid coil in the ABS hydraulic modulator
20%
Cross-pin contact or contamination in the modulator connector allowing B+ voltage from an adjacent circuit to feed into the valve circuit
15%
ABS control module internal failure causing voltage feedback on the rear outlet valve driver
Diagnostic Steps
1
Disconnect both the ABS modulator connector and the ABS module connector. With a DVOM set to DC voltage, check each rear outlet valve solenoid wire for battery voltage. Any voltage present confirms an external short to a power source.
2
With connectors unplugged, measure rear outlet valve solenoid coil resistance (spec: 3-6 ohms). Also check insulation from each pin to the connector shell ground and to each adjacent pin.
3
Trace the wiring harness for the rear valve circuit. Inspect areas near the fuse box, along the engine compartment firewall, and near any power distribution points where the harness may contact B+ wiring.
4
Repair any damaged insulation or crossed wires. Use proper automotive-grade splicing and heat-shrink sealant tubing to ensure a weatherproof repair.
5
Clear codes, verify proper solenoid operation via bidirectional scan tool test if available, and road test for ABS functionality.
Estimated Repair Cost
$100 - $1,100
Parts + labor, varies by vehicle and location
The ABS module has detected a short-to-battery-voltage condition on the rear outlet valve solenoid coil circuit. Unwanted voltage on this circuit prevents proper ABS modulation of rear brake pressure. The ABS system is disabled and the dashboard ABS warning lamp is illuminated. Standard braking cont...
The most common cause of C1204 (ABS Outlet Valve Coil Rear Circuit Short To Battery) is: Wiring harness chafed or melted against a nearby B+ power feed wire, creating a short to voltage on the rear outlet valve circuit
Typical repair costs for C1204 range from $100 to $1,100, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Normal braking remains functional but ABS is completely disabled. A short-to-battery condition may also risk wire overheating. Rear wheel lockup is possible during hard braking, which can cause vehicle instability. Repair promptly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1204 to identify the root cause.
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Quick Info
Category
Chassis
System
ABS / Traction Control
Difficulty
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