U2193

Code

Generic U — Network/User

Lost Communication with Vehicle Control Module

Brand: Generic

Type: U — Network/User

Views: UK: 16 EN: 28 RU: 24

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Failed or powered-off control module
Open, shorted or damaged communication wires (CAN_H/CAN_L or LIN)
Poor power or ground to the module (fuse, relay, battery connection)
Corroded or loose connector pins at the module or splice
Bus termination fault (missing or shorted termination resistor)
Network voltage abnormality (battery low or charging system issue)

Symptoms

One or more systems controlled by the affected module inoperative or degraded
Warning lights or messages on the dash (may vary by vehicle)
Scan tool cannot communicate with the affected module
Multiple network-related DTCs present
Intermittent function loss (works sometimes, then fails)
Vehicle may enter limp or reduced functionality mode

What to check

Confirm current and pending U2193 with an OEM-capable scan tool and note freeze-frame and related codes
Verify battery voltage and charging system (engine off and cranking/idle)
Inspect relevant fuses and relays for the affected module
Visually inspect module connectors and wiring for corrosion, damage, pin push-out or water
Attempt to communicate with the module via the scan tool; try other network nodes to confirm bus health
Measure CAN/LIN bus voltages and differential with a multimeter or oscilloscope

Signal parameters

CAN bus idle (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (both near mid-rail)
CAN bus dominant: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
Typical CAN bus termination: ≈ 60 ohms measured across CAN_H and CAN_L with ignition off
Common CAN data rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific rate)
LIN bus idle: ≈ battery voltage on master wire, wake pulses are single-wire serial levels (vehicle-specific)

Diagnostic algorithm

Record all DTCs and freeze-frame data with an OEM-capable scan tool. Note whether code is current or historic and whether it is intermittent.
Attempt to communicate with the reported module from the scan tool. If communication is present intermittently, monitor while performing wiggle tests on harnesses.
Check battery voltage (should be ~12.4–12.8 V at rest). Verify charging system at idle (~13.5–14.8 V). Low system voltage can cause comm loss.
Inspect and secure all fuses and relays supplying power/ignition to the affected module. Verify module receives switched battery power and a good ground at the harness connector.
Visually inspect connectors and wiring between the module and the nearest splice/junction for damage, corrosion, or water intrusion. Repair as needed.
With ignition ON, measure CAN_H and CAN_L at the module connector and at another known-good network node. Compare voltages and look for missing or abnormal levels.
With ignition OFF, measure resistance across CAN_H and CAN_L at an accessible harness to verify ≈60 ohms. If open or extreme low, trace for missing termination or short.
If a short to battery or ground is suspected, isolate sections of the bus (disconnect modules one at a time, where practical) to locate the shorted segment.
If wiring and power/ground are good but the module still will not communicate, check for software/firmware updates or module configuration issues per manufacturer guidance.
Replace or reprogram the module only after verifying wiring and power/ground are correct. After repairs, clear codes and perform a drive cycle or functional test to confirm resolution.

Likely causes

Blown fuse or disabled module power/ignition feed
Damaged connector at the affected module (bent pins, corrosion)
Shorted CAN wires to battery or ground near harness routing
Faulty ground(s) common to the module and network
Bus termination resistor open or shorted causing bus-off condition

Fault status

⚠️ Status

Lost communication with vehicle control module detected on the vehicle network. The module is not responding or is offline; related systems may be inoperative.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-3.0 hours