C1B25

Code

Generic C — Chassis

Chassis Control Module — CAN bus message timeout

Brand: Generic

Type: C — Chassis

Views: UK: 3 EN: 1 RU: 4

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Page language: EN

Causes

Open, short, or high resistance in CAN_H/CAN_L wiring or connector pins
Corroded or loose connector(s) at the CCM or the transmitting module
Failed or sleeping transmitting module (ECU that should send the message)
Incorrect or missing termination (bad/missing 120 Ω resistor or parallel pair ≈60 Ω)
Low battery voltage or intermittent power/ground to a module
Bus overload or excessive noise (shorts to battery/chassis, improper splices, aftermarket devices)

Symptoms

Warning or communication-related lamp(s) illuminated (e.g., traction/ABS, stability)
Loss or intermittent operation of chassis systems (ABS, traction control, stability, steering assist)
Module(s) missing or reporting multiple communication errors on a scan tool
Features that depend on the missing message are inactive or intermittent
No expected periodic CAN messages seen with a network monitor/oscilloscope

What to check

Read and record all stored DTCs and freeze frame data from CCM and other modules
Note time/date and conditions when timeout occurred (speed, ignition state, active subsystems)
Identify which module/message ID CCM expects (refer to wiring/communications documentation)
Visually inspect connectors and wiring at CCM and the suspected transmitting module for corrosion, bent pins, water damage, or loose terminals
Measure vehicle battery voltage and check module power and ground integrity
With ignition on, measure CAN_H and CAN_L voltages (idle) and check termination resistance between CAN_H and CAN_L (vehicle off)

Signal parameters

High-speed CAN common bit rates: typically 500 kbps (common) or 250/125 kbps depending on vehicle architecture
Idle voltages: CAN_H and CAN_L ≈ 2.5 V relative to chassis (each), with dominant state producing ≈ CAN_H 3.5 V and CAN_L 1.5 V (differential ≈ 2 V)
Termination: two 120 Ω resistors in parallel (≈60 Ω between CAN_H and CAN_L) when harness is connected
Expected message interval: many chassis messages repeat every 10–100 ms (manufacturer-specific)
Message identifiers (IDs) and sending module vary by vehicle — check manufacturer network map

Diagnostic algorithm

Connect a full-function scan tool and record all DTCs and freeze-frame data from CCM and other modules. Note any other communication-related codes.
Identify which message ID or sender module the CCM timed out on (consult wiring/communication documentation).
Verify vehicle battery voltage (engine off and cranking) and check power and ground at the CCM and the identified sender module. Repair any low supply or poor ground first.
Visually inspect and physically wiggle connectors and harnesses on CCM and sender module while monitoring the bus for changes. Repair/clean/secure any damaged connectors.
With ignition on, measure CAN_H and CAN_L idle voltages at the CCM and at the suspect module. Compare readings; large differences indicate wiring/power issues.
With vehicle off, measure resistance between CAN_H and CAN_L at key harness connectors — expect ≈60 Ω for the whole high-speed bus. If open or very high, investigate missing termination or open circuit.
Use an oscilloscope or CAN bus analyzer to confirm presence/absence of the expected message, check bit rate, waveform integrity, and look for noise or dominant errors. Note whether other modules are transmitting normally.
Isolate sections by disconnecting harness branches or modules (one at a time) to find the segment causing the timeout. Avoid creating open circuits on other required networks; follow safety/manufacturer procedures.
If wiring and terminations are good and message is not present, test or swap (if available) the suspected sender module or reprogram/flash module software per manufacturer instructions.
After repairs, clear DTCs, perform a drive cycle or reproduce conditions, and re-scan to confirm the timeout does not return.