B3623

Code

Generic B — Body

Seat Memory Module Communication Fault

Brand: Generic

Type: B — Body

Views: UK: 2 EN: 6 RU: 0

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Page language: EN

Scan vehicle network for active modules and read freeze frame/related U-codes
Check for additional DTCs on BCM, gateway, and seat modules
Visually inspect seat wiring harness and connectors for damage, corrosion, or loose pins
Verify fuses and relays feeding the seat memory module
Back-probe module power and ground pins with ignition on and during fault
Wiggle harness and operate seat while monitoring for code set or intermittent comm

CAN bus idle voltages: CAN_H ≈ 2.5 V (recessive), CAN_L ≈ 2.5 V; dominant approx. CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V
Typical module message rate: varies by manufacturer (often periodic 1–10 Hz when awake)
LIN bus: single-wire ~0–12 V signal with wake/pulse patterns (if seat memory uses LIN)
Module supply: battery/ignition voltage near 12 V at power pin with ignition on
Ground: continuity to chassis < 1 Ω; voltage drop under cranking should be minimal
No bus errors on scope: look for missing frames, distorted edges, or excessive error frames

Read and record all DTCs from all modules (BCM, gateway, seat, airbags if applicable).
Confirm vehicle symptoms and whether fault is current, pending, or historic (freeze frame).
Visually inspect seat connectors, harness routing through the seat and into the door sill/underseat areas for chafing or water.
Check fuses and measure battery voltage at the seat memory module power pin with ignition on.
Verify ground integrity at the module by measuring voltage drop while operating seat/memory function.
Use a scan tool to poll the seat memory module. If module not present, try waking network or cycling ignition per service manual.
With a DSO/oscilloscope or CAN bus tester, observe CAN_H and CAN_L at the module connector for proper recessive/dominant levels and valid frames. Look for CAN errors or loss of frames when moving the seat.
If LIN is used, check LIN line for proper wake pulses and data when commanding seat memory functions.
If wiring and power/ground OK but no communication, disconnect module and check for short to Vb or ground on network lines, then consider module replacement or reflashing.
After repair, clear codes and perform full system test including memory save/recall and road test to confirm failure does not return.