C1246 on 2003-2009 Toyota 4Runner — Master Cylinder Pressure Sensor Malfunction
1 vehicles · 1 makes · $1,200-$3,000 repair
Most Reported On
C1246 is an OBD-II diagnostic trouble code meaning “Master Cylinder Pressure Sensor Malfunction.” A Toyota/Lexus chassis code, shown in factory manuals as DTC C1246/46. The skid control ECU judged the master cylinder pressure sensor signal to be missing, erratic, stuck, or inconsistent with the stop light switch — this sensor converts hydraulic brake pressure into a voltage the ECU uses to know how hard the driver is braking. On most applications the sensor is built into the brake actuator assembly, not serviced separately. As a fail-safe the ECU disables ABS, traction control and VSC and lights the associated warning lamps; normal hydraulic braking remains, but the electronic assists are off. This code is most commonly reported on 2003-2009 Toyota 4Runner, with repair costs ranging from $1,200 to $3,000.
Common Causes
Typical Repair Cost
Based on 1 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
C1246 does not use the standard P/B/C/U prefix. It may be a manufacturer-specific code, so verify that a scanner supports your exact year, model and module before buying.
FAQ
What does C1246 mean?
C1246 stands for "Master Cylinder Pressure Sensor Malfunction." A Toyota/Lexus chassis code, shown in factory manuals as DTC C1246/46. The skid control ECU judged the master cylinder pressure sensor signal to be missing, erratic, stuck, or inconsistent with the stop light switch — this sensor converts hydraulic brake pressure into a voltage the ECU uses to know how hard the driver is braking. On most applications the sensor is built into the brake actuator assembly, not serviced separately. As a fail-safe the ECU disables ABS, traction control and VSC and lights the associated warning lamps; normal hydraulic braking remains, but the electronic assists are off.
What are the most common causes of C1246?
The most common causes of C1246 are: Failed master cylinder pressure sensor — on most Toyota/Lexus applications it is integral to the brake actuator assembly, Open or shorted wiring in the brake actuator / skid control ECU harness, Poor or corroded connector contact at the brake actuator or skid control ECU, Failed skid control ECU (brake actuator assembly), Low system voltage or a poor ground skewing the sensor signal, Stop light switch fault or misadjustment causing a signal-vs-brake-switch inconsistency. The specific cause varies by vehicle.
How much does it cost to fix C1246?
Repair costs for C1246 range from $1,200 to $3,000, depending on the vehicle and root cause.
Which vehicles are affected by C1246?
Au7o has documented C1246 across 1 vehicle models from 1 manufacturers: Toyota.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.