B0205

Code

Generic B — Body

BCM power supply voltage low

Brand: Generic

Type: B — Body

Views: UK: 7 EN: 13 RU: 9

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Page language: EN

Causes

Weak or discharged battery
Poor battery terminal connection or corroded cables
Faulty or weak alternator/charging system
Blown or corroded fuse or fusible link in BCM power feed
High-resistance or broken power feed wire to the BCM
Poor or corroded ground(s) related to BCM

Symptoms

Illuminated instrument cluster warning lamp(s) or DTC stored
Loss or intermittent operation of body functions (lights, wipers, windows, locks)
Erratic or no communication with BCM on diagnostic tool
Flickering or dim interior/exterior lights
Difficulty starting or accessories dropping out during cranking
Unintended resets of body systems or random faults

What to check

Read and record freeze frame and all stored DTCs and module comms status
Measure battery voltage at battery posts (engine off, key on, engine running)
Visually inspect battery terminals, battery condition, and cable routing
Check alternator charging voltage and perform charging system test
Inspect and verify continuity of fuses/fusible links supplying the BCM
Measure voltage at the BCM power input pin(s) and compare to battery

Signal parameters

Battery voltage, engine off (rest): typically ~12.4–12.8 V
Battery voltage, key ON engine off: should be near battery resting voltage (within ~0.5 V)
Charging voltage, engine running: typically ~13.5–14.8 V
Cranking voltage: commonly 9.0–11.5 V depending on starter load and battery state
BCM main power pin: should read within ~0.5 V of the battery post under comparable key/engine conditions
Low-voltage condition: code set when BCM supply falls below manufacturer threshold or is intermittent

Diagnostic algorithm

Connect a scan tool. Record B0205 freeze frame and any related codes (P0562, Uxxxx, other body codes). Note engine/key state when the fault occurred.
Visually inspect battery, terminals, and cables. Clean and secure terminals if corroded or loose.
Measure battery voltage at the posts with engine off. If below ~12.4 V, charge battery and retest; perform battery load test if necessary.
Start engine and measure charging voltage at the battery. If outside ~13.5–14.8 V, diagnose charging system (alternator, regulator).
With key ON and engine off, measure voltage at the BCM power feed pin(s) and compare to battery. If significantly lower, trace power feed: check fuses, fusible links, relay contacts, and continuity to the battery.
Inspect and measure resistance/continuity of BCM ground(s). Clean and secure ground connections and retest voltage behavior.
Wiggle connectors and wiring harness while monitoring BCM voltage and module communication for intermittent changes. Repair or replace damaged wiring/connectors.
If low voltage only during cranking, test starter draw and connections; inspect battery condition and cable sizing.
Check for parasitic current draw if battery drains or low-voltage condition occurs with vehicle parked. Isolate circuits to find source.
If wiring, fuses, grounds, battery and charging system are within spec and the low voltage persists at the BCM, consider replacing the BCM following manufacturer procedures and programming.
After repairs, clear codes and perform a road/operation test to confirm B0205 does not return and related symptoms are resolved.