U2197

Code

Generic U — Network/User

Lost Communication With Control Module

Brand: Generic

Type: U — Network/User

Views: UK: 23 EN: 35 RU: 31

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Page language: EN

Causes

Open or shorted wiring on the vehicle data bus
Faulty or corroded connector(s) at the affected module
Missing or low power or ground to the module
Bus termination resistor(s) missing or damaged
Module in sleep, bus-off state, or software fault
High electrical noise or bus contention from another device

Symptoms

Malfunction indicator lamps related to that module (may or may not illuminate)
Loss of functionality controlled by the module (e.g., ABS, traction, climate, gateway functions)
Intermittent or permanent faults stored in multiple modules
No response when querying the module with a scan tool
Multiple network-related DTCs present

What to check

Read all stored and pending DTCs and freeze frame from all modules; note network-related codes
Confirm which physical network (CAN, LIN, FlexRay, etc.) and message ID(s) are affected
Verify battery voltage and chassis/body/engine grounds with key on
Visually inspect connectors and harness for damage, corrosion, or recent repair work
Check for presence of termination resistors or expected bus resistance (~60 ohms across CAN_H and CAN_L with key off) at two termination points
Attempt communication with the module using a diagnostic tool; note tool error or timeouts

Signal parameters

Battery voltage at module (V) — should be within specified range (typically 11–15 V)
CAN differential voltage (CAN_H – CAN_L) during active bits — expected ~2.5 V differential with dominant ~3.5 V/1.5 V levels
CAN_H and CAN_L individual voltages with respect to ground (idle ~2.5 V each)
Bus resistance between CAN_H and CAN_L with ignition off — typically ~60 ohms (two 120 ohm terminators in parallel)
Bit rate of bus (e.g., 250 kb/s, 500 kb/s) and consistency of timing
Error frame rate and node bus-off counters seen on scope or tool

Diagnostic algorithm

Record current DTCs and symptoms from all modules. Identify the affected control module and network.
Verify battery voltage and good grounds at vehicle reference points and at the suspected module connector. Repair any low voltage or bad ground.
Visually inspect module connectors, pins, and wiring for damage, corrosion, bent pins, or water ingress. Repair or replace damaged connectors/wiring.
With ignition off, measure resistance between CAN_H and CAN_L at a convenient access point; compare to expected (~60 Ω). If abnormally high or open, trace for missing terminator or open line.
With key on and engine as required, use a scan tool to request data from the module. If no response, monitor the bus with an oscilloscope or CAN sniffer to check for proper recessive/dominant voltages, message traffic, and error frames.
If bus shows contention, short, or noise, isolate sections of the bus by disconnecting nodes/modules one at a time (where allowed) until the network returns to normal; identify the faulting harness or module.
If a specific module is not transmitting but has proper power/ground and the bus is healthy, attempt a module reset/power-cycle and reprogram or update firmware per manufacturer procedures.
Replace the module only after confirming wiring, power/ground, and bus integrity. After repairs, clear codes, perform relearn if required, and test drive to confirm the fault does not return.
If intermittent, perform wiggle tests and stress tests (door cycle, engine vibration) while monitoring bus traffic to reproduce the issue.