Code
C1A1A
Generic
C — Chassis
Chassis Control Module — Internal Communication Fault
AI status
Completed
Completed
100%
Causes
- Internal module hardware or firmware fault
- Loss or instability of module power supply (battery, fuse, D‑sub pins)
- Poor ground or high ground resistance at module
- CAN/LIN bus wiring fault, short, or open
- Corroded/loose connector or damaged pins at module
- Software mismatch or corrupted calibration data
Symptoms
- MIL or chassis warning lamp illuminated
- Loss of chassis-related features (stability control, ABS messages, air suspension, etc.)
- Other modules reporting loss of communication with CCM
- Intermittent faults that may clear after ignition cycle
- Stored internal diagnostic entries or permanent fault flags
- Possible vehicle limp mode or degraded handling functions
What to check
- Read full DTC list and freeze frame data with a capable scan tool
- Check for related network communication codes (U0xxx, U01xx)
- Verify battery voltage (>12.4 V recommended) and charging system
- Inspect CCM connector for corrosion, bent pins, water, or debris
- Check fuses and relays feeding the CCM
- Backprobe or measure power and ground pins at the CCM connector
Signal parameters
- Battery/ignition supply voltage to CCM (nominal ~12 V)
- Ground resistance at CCM chassis ground (
- CAN bus idle voltages: CAN_H ≈ 2.5–3.5 V, CAN_L ≈ 1.5–2.5 V
- CAN differential voltage during communication (expected pulses up to ~2 V)
- Bus error counters and message rate for CCM ID on network
- Module wake/sleep state and response to diagnostic poll
Diagnostic algorithm
- Connect a manufacturer-capable scan tool and capture all DTCs, freeze frame, and live data. Note occurrence frequency and related codes.
- Check battery state of charge and charging system. If voltage is low, charge/replace battery before further testing.
- Visually inspect CCM connector and harness for damage, water, corrosion, or loose fasteners. Repair as needed.
- Verify fuses/relays supplying the CCM. Replace any blown fuses and retest.
- Backprobe CCM power and ground pins with DVOM; verify stable supply and low ground resistance. Wiggle harness while monitoring for changes.
- Use an oscilloscope or high-speed data logger on CAN_H and CAN_L at the CCM connector. Look for proper idle levels, differential pulses, excessive noise, or missing messages.
- If bus signals are abnormal, isolate by disconnecting segments or modules to find short/open. Repair wiring or connectors found faulty.
- If wiring and power/ground verify good but CCM is not responding or reports internal errors, check for available software updates and attempt a controlled reflash or reprogram per OEM procedure.
- If reflashing fails or module shows persistent internal faults, consider replacement of the CCM. If replaced, follow module coding/initialization procedures and retest network communication.
- Clear DTCs, perform functional tests and road test to confirm repair. Monitor for return of the fault.
Likely causes
- Failed CCM processor or memory (internal fault)
- Blown fuse or weak battery causing undervoltage at module
- High resistance ground at module chassis connection
- CAN high/low short to battery or ground or open circuit
- Damaged connector pins or corrosion on harness connector
- Previous improper programming or interrupted reflashing
Fault status
Status
Chassis Control Module — Internal Communication Fault (module not responding or internal communication error)
Repair difficulty: Hard
Diagnostic time: 1.5-4.0 hours
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