C0501moderate severityChassis
Transfer Case Control Module Communication
on 2003 Mazda Protege 1.6L I4 · FWD
What this code means
Loss of communication between the transfer case module and other vehicle systems.
Symptoms
- 4WD light flashing
- Service 4WD warning
- Cannot select drive modes
- Transmission may default to limp mode
Common causes
- CAN bus wiring fault to module
- Module connector disconnected
- Module power loss
- CAN bus termination issue
Diagnostic steps
- Check CAN wiring to transfer case module
- Inspect module connector
- Verify power and ground at module
- Look for U-codes related to transfer case
- Check CAN bus resistance
Repair notes
Repair CAN wiring or connector. Replace module if communication chip failed.
Other Chassis codes on this vehicle
C0021
LF Wheel Speed Sensor Range/Performance
C0022
RF Wheel Speed Sensor Range/Performance
C0023
LR Wheel Speed Sensor Range/Performance
C0024
RR Wheel Speed Sensor Range/Performance
C0025
LF Wheel Speed Sensor Circuit Intermittent
C0026
RF Wheel Speed Sensor Circuit Intermittent
C0027
LR Wheel Speed Sensor Circuit Intermittent
C0028
RR Wheel Speed Sensor Circuit Intermittent
C0035
Left Front Wheel Speed Sensor Circuit
C0036
Left Front Wheel Speed Signal Erratic