What Does C1203 Mean?
The ABS module has identified an open circuit in the rear outlet valve solenoid coil. The electrical path through the solenoid winding is broken, preventing the ABS module from energizing the valve to release rear brake pressure during ABS activation. ABS is disabled and the warning lamp is illuminated.
Common Causes
35%
Internally broken rear outlet valve solenoid coil winding inside the hydraulic modulator
30%
Broken or disconnected wire in the harness between the ABS module and the modulator for the rear outlet valve circuit
25%
Corroded or backed-out terminal in the ABS modulator connector on the rear outlet valve circuit
10%
ABS module internal open on the rear outlet valve driver output
Diagnostic Steps
1
Disconnect the ABS modulator connector. Measure the rear outlet valve solenoid coil resistance across the designated pins (spec: 3-6 ohms). An infinite/OL reading confirms an open coil.
2
If the coil reads within spec, check for continuity on each wire from the ABS module connector to the modulator connector. An open wire needs to be traced and repaired.
3
Inspect the modulator and ABS module connectors for backed-out pins, corrosion, or physical damage. Ensure each terminal is fully locked in the connector housing.
4
If the coil is confirmed open, replacement of the ABS hydraulic modulator is required. The solenoid coils are internal and not individually replaceable.
5
After replacement, bleed the ABS system per factory procedure (often requires a scan tool to cycle the pump and valves), clear codes, and verify operation.
Estimated Repair Cost
$150 - $1,200
Parts + labor, varies by vehicle and location
The ABS module has identified an open circuit in the rear outlet valve solenoid coil. The electrical path through the solenoid winding is broken, preventing the ABS module from energizing the valve to release rear brake pressure during ABS activation. ABS is disabled and the warning lamp is illumina...
The most common cause of C1203 (ABS Outlet Valve Coil Rear Circuit Open) is: Internally broken rear outlet valve solenoid coil winding inside the hydraulic modulator
Typical repair costs for C1203 range from $150 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Conventional braking is fully functional. ABS is disabled, which means both rear wheels may lock during emergency stops, potentially causing the rear of the vehicle to slide out. This is particularly dangerous in curves and on slippery surfaces.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1203 to identify the root cause.
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Quick Info
Category
Chassis
System
ABS / Traction Control
Difficulty
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