U024C

Code

Generic U — Network/User

Lost Communication With Seat Control Module H

Brand: Generic

Type: U — Network/User

Views: UK: 27 EN: 87 RU: 28

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Faulty or unpowered seat control module
Open, shorted or corroded wiring/connectors to the seat module
Blown fuse or missing module supply/ground
CAN/LIN bus wiring fault (open, short to battery/ground, short to CAN/LIN high/low)
Missing or bad termination resistor on the vehicle network
Faulty gateway/BCM or other network node interfering with messages

Symptoms

Seat adjustment, heating, memory or lumbar functions inoperative or intermittent
Seat-related warnings or message on the instrument cluster
Other modules report lost-communication codes or degraded features
Stored U024C (and possibly related network U-codes) in one or more modules
Erratic or no response from seat controls

What to check

Read all diagnostic trouble codes from all modules and record freeze frame data
Verify battery voltage (12–14.5 V) and stable supply while testing
Visually inspect seat module connectors and harness for damage, corrosion, or loose pins
Check fuses and power/ground circuits for the seat module
Verify presence of CAN/LIN bus signals at the seat module connector with a scope or multimeter
Check termination resistors across CAN_H and CAN_L (approx. 60 Ohm combined) with ignition off

Signal parameters

CAN bus idle voltages: CAN_H ~2.5 V, CAN_L ~2.5 V (with typical quiescent common mode ~2.5 V)
Differential CAN voltages during traffic: CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V depending on recess/mark bits
Combined termination resistance between CAN_H and CAN_L ≈ 60 ohms with ignition off (two 120 Ω resistors in parallel)
LIN (if used) expected idle voltage near battery (varies by vehicle) and pulsed messages when active
No short to battery or ground on CAN_H or CAN_L (should not read near 12 V or 0 V respectively under normal conditions)

Diagnostic algorithm

Verify and record all stored U-codes and related module DTCs. Note when U024C is set (key on, driving, sleeping).
Clear codes and attempt to re-create the fault while monitoring network traffic with a capable scan tool or oscilloscope.
Confirm seat module supply and ground pins have proper battery voltage and good chassis/return ground. Check fuses and fusible links.
Inspect and secure the module connector(s). Backprobe pins to confirm power, ground and network signal presence.
Measure CAN_H and CAN_L (or LIN) at the seat module connector with ignition on and while operating seat functions. Look for correct idle and active levels and absence of shorts.
Check for correct termination resistance across the CAN bus at two points (combined ~60 Ω). If termination is open or shorted, trace wiring harness toward ECU/gateway.
If bus wiring appears intact, disconnect the seat module and see if bus health changes (other modules may resume normal traffic). Reconnect and check for module-induced bus faults.
Inspect harness routing for chafing or pinched sections, especially where the seat harness passes through the body or under the seat.
If wiring and power are good but the seat module does not communicate, try updating module software or reprogramming if a known software issue exists, or replace the module following manufacturer procedures.
After repairs, clear codes and verify normal operation of seat functions and that U024C does not return. Re-run network diagnostics to ensure no additional faults.