B0270

Code

Generic B — Body

Body Control Module — Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 6 EN: 12 RU: 8

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Page language: EN

Causes

Intermittent or low battery/voltage supply
Blown fuse or failed power/ignition relay feeding the BCM
Poor ground or high resistance at BCM ground(s)
Corroded, loose or damaged BCM connector or wiring harness
CAN/LIN bus communication errors or short to voltage/ground
Moisture intrusion or physical damage to the BCM

Symptoms

BCM-related functions inoperative or intermittent (interior lights, door locks, wipers, DRLs, etc.)
Multiple unrelated modules show communication faults or limp functionality
Warning lights on dash (BCM, ABS, airbag, or multiple system warnings)
Keyless entry, remote start, or immobilizer issues
Incorrect or random operation of body functions
Stored B0270 code with limited or no other specific input-sensor faults

What to check

Read all stored and pending DTCs, including communication and U-codes, with a capable scan tool and note freeze-frame data
Verify and record battery voltage with key OFF and key ON (battery resting and charging system voltage)
Inspect BCM fuses and associated relays; tug and reseat relays if applicable
Visually inspect BCM connector(s) for corrosion, bent pins, water, or push-out pins; check for signs of overheating
Check primary ground(s) and power feeds to the BCM for tightness and continuity
Scan CAN/LIN bus status on the tool: note lost messages, bus errors, or bus off conditions

Signal parameters

Battery/rest voltage: ~12.4–12.8 V (engine off); charging system ~13.5–14.8 V (engine running)
Ignition-switched supply: should be present with key ON (consult wiring diagram for expected pin voltages)
Ground resistance: BCM ground(s)
CAN bus idle voltages (typical): CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V; dominant state difference ≈1.5–2.0 V (verify against OEM spec)
LIN bus idle: near battery ground or near 12 V depending on topology — check OEM spec
Module wake/sleep control signal levels per vehicle wiring diagram

Diagnostic algorithm

Capture all codes and freeze-frame data with a capable scan tool; save or print results. Check for related U-codes (lost comms) and other B-codes.
Verify battery state-of-charge and charging system. Charge battery to full and re-check code if low voltage was present.
Inspect and verify fuses and relays supplying the BCM. Replace any blown fuses and re-test.
Visually inspect BCM connectors and wiring harness for corrosion, bent pins, water intrusion or damage. Repair or clean as needed and reseat connectors.
Verify power and ground at the BCM pins with DVOM: check switched and constant supplies and ground continuity. Repair any open/high-resistance circuits.
Check CAN/LIN bus health: use a scope or scan tool to view bus signals, look for bus errors, verify termination resistances and that other modules respond. Repair wiring faults.
Clear codes and attempt to reproduce the fault. If code returns, note conditions (temperature, after start, during accessory use).
Attempt a controlled power-cycle or BCM reset per OEM procedure (battery disconnect or scan-tool module reset) and re-check. Do not replace module solely on intermittent codes without proper verification.
Check for software updates, TSBs or reflash procedures. If software corruption likely, reprogram/reflash BCM per OEM guidance.
If internal memory/processor is confirmed failed after all above checks, consult OEM for repair/replacement and follow required module coding/programming and immobilizer pairing procedures. Replace BCM only as last resort and ensure proper programming and network re-initialization.