C1786

Code

Generic C — Chassis

Chassis Control Module Communication Fault

Brand: Generic

Type: C — Chassis

Views: UK: 16 EN: 16 RU: 10

AI status

Completed

ready

Completed 100%

Page language: EN

CCM-related warning lamp(s) (ABS, ESC, traction) illuminated or flashing
Loss of ABS/traction/stability functions or messages about degraded chassis systems
Stored communication fault(s) and possibly multiple modules reporting comm errors
Intermittent or permanent disablement of chassis features
Possible no-communications response when scanning CCM

Read all modules and freeze-frame data with an OEM-level scan tool
Check for additional U- or C-class communication codes
Visually inspect CCM connector(s) and nearby harness for damage, corrosion, or water intrusion
Verify battery voltage and CCM power feed fuses/relays
Check CCM ground(s for tightness and corrosion)
Measure CAN/LIN bus voltages and resistance across termination resistors (~60 ohms for CAN)

Battery supply to CCM: ~11–14.5 V (with engine off/running as appropriate)
CAN bus idle: both CAN_H and CAN_L near recessive voltage (~2.5 V each)
CAN dominant state: CAN_H rises toward ~3.5 V while CAN_L falls toward ~1.5 V (observed during activity)
CAN bus termination: ~60 ohms between CAN_H and CAN_L (two 120Ω in parallel)
Typical CAN data rates: 250 kb/s or 500 kb/s (verify vehicle specification)

Connect a capable scan tool and record all stored codes and freeze-frame data; note time stamps and related modules.
Confirm other modules on the same network and check for multiple communication faults to narrow scope.
Perform visual inspection of CCM connector, harness, and nearby grounds for corrosion, loose pins, or water entry; repair as needed.
Verify CCM power and ground: measure battery voltage at the module power pin and check ground resistance to chassis (
With ignition ON, measure static CAN_H and CAN_L voltages at the CCM connector; expect ~2.5 V each. If not, inspect wiring to the network or module supply.
Check CAN bus termination resistance between CAN_H and CAN_L; expect ~60 ohms. Replace missing/failed termination or repair wiring.
Use an oscilloscope or scan tool to observe bus activity while trying to communicate; look for noise, missing frames, or dominant states.
Isolate by disconnecting suspect nodes/modules one at a time (where safe) to see if communication is restored — helps locate a shorted or noisy module.
If wiring, connectors, fuses, relays and termination are good but comms still fail, consider replacing or reprogramming the CCM per manufacturer procedures.
Clear codes and road-test to confirm repair; monitor for recurrence.