B2897

Code

Generic B — Body

Interior Lighting Control Module Communication Fault

Brand: Generic

Type: B — Body

Views: UK: 10 EN: 12 RU: 8

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Page language: EN

Causes

Faulty interior lighting control module (internal failure)
Open/shorted or corroded connectors or wiring to the module
Loss of power or ground to the module (blown fuse, poor ground)
CAN/LIN bus wiring fault, missing termination or short to reference/battery
Network gateway or other module failure interrupting messages
Aftermarket accessory interference or improper installations

Symptoms

Interior lighting not working or operating intermittently
Dash or overhead lights fail to illuminate or behave erratically
Related body functions controlled by the module inoperative (dimming, courtesy lights)
Several modules show communication faults or ‘no response’ on scan tool
Stored communication-related network DTCs (U-codes or other B-codes)
Possible parasitic battery drain if module is stuck awake

What to check

Read all stored DTCs and freeze frame with a capable scan tool; note related U- or B-codes
Verify battery voltage (key off and key on) — ensure proper supply (nominal >12.4 V at rest, >13.2 V when running)
Inspect fuses and fusible links powering the interior lighting module
Visually inspect module connector for corrosion, bent pins, water intrusion, or damage
Check module power and ground circuits for continuity and good connector contact
Scan network traffic: attempt to communicate with the module; note response/timeout

Signal parameters

CAN bus idle voltages (approx): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V; dominant state CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V
Expected CAN differential voltage when messages active: ~2.0 V differential
Common CAN data rates: 125 kb/s, 250 kb/s, 500 kb/s (verify vehicle-specific rate with scan tool)
LIN bus: single-wire wake/sleep patterns and 0–12 V nominal signaling (if module uses LIN)
Module supply voltage: nominal battery voltage when key on (check for wake/sleep current behavior)
Termination: CAN network total ~60 ohms between CAN_H and CAN_L (two 120-ohm terminators in parallel)

Diagnostic algorithm

Verify and record the exact DTC and any related codes. Attempt to communicate with the module using a scan tool.
Check battery voltage and verify fuses/power feeds for the interior lighting module. Replace any blown fuses and retest communications.
Visually inspect the module connector and harness; disconnect and inspect pins for corrosion, bent pins, or water damage.
Confirm good ground(s) and power at the module connector (use a DVOM). Repair poor grounds or open power circuits.
Measure CAN_H and CAN_L at the module connector with key on. Look for expected idle voltages and differential during activity. If voltages are abnormal, trace wiring for short/open.
If intermittent, perform a wiggle test on harnesses and connectors while monitoring live network traffic—look for message dropouts or noise.
Check termination resistance across CAN_H–CAN_L (should be ~60 ohms). Repair missing or damaged terminators.
If bus wiring and power/grounds are good but module does not respond, try swapping with a known-good module (if available) or connect a known-good device to verify network integrity.
Review recent vehicle work or aftermarket installs that could affect the body network and isolate/remove them if suspected.
If module replacement is required, follow OEM procedures for module programming/reflashing and security pairing. Clear codes and verify repair under all operating conditions.
If problems persist, capture oscilloscope traces of the bus during failure and escalate to manufacturer-specific diagnostics or wiring diagrams.

Likely causes

Loose, corroded, or partially disconnected connector at the lighting module
Blown fuse or low battery voltage causing module not to power up
Damaged CAN/LIN wiring harness or short to ground/battery on the bus
Faulty CAN/LIN termination resistor (open or high resistance)
Interior lighting control module internal electronics failure
Interference/short from recently installed aftermarket equipment

Fault status

⚠️ Status

Communication fault: interior lighting control module not responding or messages missing on vehicle network. Set when expected network messages from the module are absent or time out.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours