|Trouble Code||Fault Location||Probable Cause|
|C1201||ABS Left Front Inlet Valve Coil Circuit Short to Ground (Ford, Lincoln, Mercury, Mazda)
Front Traction Control Inlet Valve Control Circuit Low (Dodge, Chrysler, Plymouth, Jeep, FIAT)
Right Front Wheel Speed Sensor Invalid Signal (Mitsubishi)
Left Front Wheel Speed Sensor Circuit Range or Performance (Chevrolet)
Vehicle Stability Control (VSC) Cancelled by Fault in Engine Control Module (Toyota, Scion, Lexus)
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What Does Code C1201 Mean?
Modern automobiles use a number of electronic control units (ECU) to deliver whatever ride quality was promised by the automaker, from powerful sports cars to efficient commuter cars. Each ECU has its own self-diagnostic system and may communicate with other ECUs on a network, such as the CAN or BEAN (controller area network or body electrical area network). If any of these ECUs experiences a fault, it stores a DTC (diagnostic trouble code) in memory. At the same time, some functionality of that particular ECU or another may be cut off or a warning light or message may be illuminated on the instrument cluster.
In the case of DTC C1201, it refers to something in chassis control, such as ABS or ESC (anti-lock braking system or electronic stability control), but it depends on the automaker as to which system and fault. Here are some common definitions for C1201:
- Ford, Lincoln, Mercury, Mazda – ABS Left Front Inlet Valve Coil Circuit Short to Ground
- Dodge, Chrysler, Plymouth, Jeep, FIAT? – Front Traction Control Inlet Valve Control Circuit Low
- Mitsubishi – Right Front Wheel Speed Sensor Invalid Signal
- Chevrolet – Left Front Wheel Speed Sensor Circuit Range or Performance
- Toyota, Scion, Lexus – Vehicle Stability Control (VSC) Cancelled by Fault in Engine Control Module
What are the common causes of code C1201?
Depending on year, make, and model, DTC C1201 may have number of causes. Here are some of the most common.
- Water Entry – In cases where this DTC refers to a wheel speed sensor fault, water entry seems to be fairly common, particularly in the connector at the wheel. Many automakers put the connector above the fender liner to prevent just this problem. Check the connector for water entry or corrosion, which can interrupt the wheel speed signal.
- Reluctor Ring – In cases where this DTC refers to a wheel speed sensor range or performance fault, broken reluctor rings are a common problem. If the ring is pressed onto the axle, rust can form between the two, causing the ring to snap. The ring usually won’t fall out, but it can spin independently of the shaft, leading to poor signal stability.
What are the symptoms of code C1201?
Again, this totally depends on the vehicle in question, but you would probably experience problems with one or more chassis control systems, such as ABS, ESC, VSC, Launch Control, or Crawl Control.
You will probably not damage anything while driving around in this condition. Additional safety systems, such as ABS or ESC, may not function.
How do you troubleshoot code C1201?
Because this DTC is manufacturer-specific, there is really no way to cover all possible diagnostic solutions, but here are a few pointers:
- Ford – Check harness for ABS module and ABS actuator. Check that connectors have no bent pins, corrosion, or evidence of water entry.
- Chevrolet, Mitsubishi – Check harness for wheel speed sensor. Check that connectors have no bent pins, corrosion, or evidence of water entry.
- Toyota – Check and repair whatever fault is setting off the MIL (malfunction indicator lamp). C1201 will automatically clear once it sees the ECM with no faults.