Code
U2140
OPEL
U — Network/User
CAN-Bus No Communication with CIM (Steering Column Module)
AI status
Completed
Completed
100%
Causes
- Open or short in CAN H or CAN L wiring between CIM and network
- Poor power or ground to the CIM (blown fuse, loose ground, low battery)
- Faulty CIM (steering column module) or failed CAN transceiver inside module
- Corroded/poor connector pins at the CIM or harness chafe in the steering column
- Missing or damaged bus termination (open/mismatched 120Ω resistors)
- Bus overloaded or noise on CAN lines (short to battery/chassis)
Symptoms
- Steering column functions inoperative (wipers, cruise, steering wheel switches, column stalks)
- Warning lights or message lamp for communication fault or multiple modules
- Impaired immobilizer/lock steering function or no-start conditions in some vehicles
- Intermittent or permanent loss of steering column related features
- Other CAN modules reporting loss-of-communication with CIM
What to check
- Read and record all stored U-codes and freeze frame data with a scanner
- Verify battery voltage with ignition ON (should be within specification) and check related fuses for the CIM
- Visually inspect CIM connector and wiring through the steering column for damage, corrosion, pin push-out or bent pins
- Check for other modules on same CAN bus (can they communicate?) using a scan tool
- Measure CAN_H and CAN_L DC voltages at the CIM connector with ignition ON (see signal parameters)
- Measure resistance across CAN_H to CAN_L with ignition OFF — expect ~60Ω (two 120Ω terminators in parallel)
Signal parameters
- Idle (recessive) voltage: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each to vehicle ground)
- Dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (approx. ±2 V differential)
- Termination resistance (ignition OFF): approx. 60 Ω between CAN_H and CAN_L (two 120 Ω in parallel)
- Expected CAN traffic: depends on vehicle/network (common bus speeds: 250 kbps or 500 kbps). Use a scope or diagnostic tool to confirm message frames and CIM message ID presence
Diagnostic algorithm
- Connect a full-function scan tool. Record all communication DTCs and note which modules report loss of CIM.
- Verify vehicle battery voltage and inspect/replace any blown fuses powering the CIM.
- Visually inspect and unclip the CIM connector; check for corrosion, bent or pushed-out pins; reconnect and secure. Check mating connector at wiring side.
- With ignition ON, measure DC voltage on CIM power and ground pins to confirm proper supply and ground.
- Measure CAN_H and CAN_L idle voltages at the CIM connector. Compare to expected values in signal parameters.
- With ignition ON, check CAN bus traffic using a scan tool or oscilloscope. Confirm whether CIM transmit frames are present. If CIM frames are absent, test for intermittent traffic while performing a wiggle test on the steering column harness.
- With ignition OFF, measure resistance between CAN_H and CAN_L at an accessible point; expected ≈60 Ω. If open or very low, investigate missing termination or short.
- Isolate fault by disconnecting downstream modules one at a time (if procedure available) to locate short or noisy node. Repair wiring, connector, or replace damaged components as identified.
- If wiring and power/ground are good and bus signals are correct at the harness but CIM does not appear on the bus, replace or reprogram CIM per manufacturer procedure.
- After repairs, clear codes and verify normal communication and restoration of steering column functions.
Likely causes
- Damaged connector or wiring in the steering column (common due to flexing)
- Blown fuse or poor ground for the CIM
- Failed CAN transceiver inside CIM
- Loss of CAN termination or short between CAN lines
Fault status
Status
U2140 — CAN bus: no communication with CIM (Steering Column Module). No valid CAN messages received from CIM; steering column functions may be unavailable.
Repair difficulty: Medium
Diagnostic time: 0.5–3.0 hours
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