Code
B1485
ALFA ROMEO
B — Body
Brake enable/disable switch circuit short to positive
Views:
UK: 4
EN: 6
RU: 3
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring contacting battery positive or a fused B+ feed
- Corroded, bridged, or damaged connector at the brake enable/disable switch
- Failed brake enable/disable switch with internal short to B+
- Shorted splice or aftermarket accessory tied into the brake circuit
- Faulty body control module (BCM) / brake module input or internal short
Symptoms
- Brake warning lamp or general instrument cluster warning
- Cruise control, start/stop or driver assist functions disabled or inoperative
- Brake lights stuck ON or intermittent operation
- Stored B1485 (or related) fault and limp functionality for affected systems
- Possible battery drain if circuit is powering unexpectedly
What to check
- Use a scan tool to confirm the DTC and freeze frame data; note conditions when fault set
- Visually inspect wiring from switch to module for damage, pinched areas, or repairs
- Disconnect the brake enable/disable switch connector and check if the code reappears
- Backprobe the switch connector and measure voltage with switch connected and disconnected
- Check for aftermarket devices spliced into the brake or lighting wiring
- Inspect related fuses and relays for signs of damage or incorrect replacement
Signal parameters
- Battery nominal (engine off): ~12.0–12.8 V
- Charging system (engine running): ~13.5–14.8 V
- Expected brake switch signal: approximately 0 V when circuit is pulled low/open, ~battery voltage when switch intentionally tied to B+ (or vice versa depending on vehicle harness design)
- Closed switch resistance: typically very low (
- Open switch resistance: very high/OL when not actuated
Diagnostic algorithm
- Read and record DTC and freeze frame with a capable scanner. Clear code and see if it returns to confirm active condition.
- Visually inspect the brake switch harness, connector and routing from switch to BCM for damage, chafing, or aftermarket splices. Repair any obvious damage.
- With ignition ON (engine off), backprobe the switch connector. Verify voltage on the switch signal pin. If voltage is equal to battery positive when it should be low, suspect a short to B+ upstream or internal to the switch.
- Disconnect the switch connector. Re-scan: if the code clears or the signal changes, the fault is likely in the switch or harness up to the connector. If the fault remains, suspect wiring between connector and module or the module input.
- Perform continuity and short-to-power tests: with battery disconnected, check continuity from the switch signal pin to B+ and to chassis ground. A low resistance to B+ indicates a short to positive.
- Isolate sections of harness by disconnecting intermediate connectors/splices and testing until the short location is found.
- If harness and connectors are good, replace the brake enable/disable switch and retest. Use OE-type replacement and confirm correct routing and connector seating.
- If problem persists after switch replacement and wiring verified, test or replace the affected control module per manufacturer's diagnostic procedure.
- After repairs, clear codes and perform functional tests (operate brake, verify brake lights, check cruise/start-stop behaviors) and a test drive to confirm repair.
Likely causes
- Chafed insulation or pinched wiring harness contacting a B+ source
- Damaged connector with corrosion causing B+ feed to be present on the switch pin
- Failed switch element internally shorted to battery
Fault status
Status
Brake enable/disable switch circuit short to positive detected — input circuit is reading battery voltage when it should not. Investigation required for short to B+ in switch wiring, connector, switch, or module.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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