What does it mean?
C1117 is a Chassis (ABS, traction control, steering) fault code. It indicates: RPM Input Circuit Failure .
Symptoms
- Tachometer needle drops to zero, jumps or reads erratically
- ABS, traction and stability warning lamps illuminated
- Cruise control unavailable or cancels on its own
- Automatic transmission shifts harshly or holds a gear
- Idle behaviour looks unstable on the display even though the engine runs smoothly
- Fault appears with engine vibration or over bumps
Likely causes
- Break or high resistance in the engine speed signal wire between the engine management side and the module
- Engine control module not transmitting the speed value because of its own stored fault
- Corroded connector or a backed out terminal on the signal circuit
- Chafed signal wire shorting to ground or picking up interference from ignition components
- Poor ground shared by the modules that exchange the speed value
- Faulty instrument cluster or gateway that relays the signal on some systems
- Internal input circuit failure in the receiving control module
How to fix it
- Compare engine speed read from the engine control module with the value the chassis module reports
- Scan every module and repair engine management faults first if the source has its own codes
- Check the signal wire for continuity, shorts to ground and shorts to battery voltage
- Inspect connectors on the circuit for corrosion, moisture and loose terminals
- Watch the signal with a scope or a graphing meter while wiggling the harness
- Clean and tighten the shared ground points for the modules involved
- Repair the wiring, then consider the sending or receiving module only after the circuit tests good