Code
B1408
ALFA ROMEO
B — Body
Front left electric window raising switch short to positive
Views:
UK: 16
EN: 26
RU: 20
AI status
Completed
Completed
100%
Causes
- Damaged wiring harness (chafing, pinched, pierced insulation) in driver door wiring loom
- Corroded or water-damaged door switch connector or terminals
- Faulty front left window switch with internal short to B+
- Shorted splice or connector in the circuit (e.g., power feed splice)
- Faulty body/comfort module or door control module (rare)
- Aftermarket equipment or previous repair introduced incorrect wiring or a hard short
Symptoms
- Front left window does not respond correctly to the UP (raise) command
- Intermittent or permanent presence of the DTC B1408
- Other window functions or door electronics may behave erratically if a shared feed is affected
- Fuse may blow or other circuits on same feed may be affected in severe shorts
What to check
- Read and record freeze frame and any related DTCs with a diagnostic scanner; clear codes and see if B1408 returns
- Visual inspection of driver door wiring harness, door hinge area (flex points) and switch connector for chafing, corrosion, bent pins or moisture
- Inspect switch for signs of water ingress, damage or melted plastic
- Check relevant fuses and power feeds for continuity and correct value
- With ignition ON, measure voltage at the switch power pin (should be approx. battery voltage ~12–14 V) and at the switch signal pin while operating the switch
- Disconnect front left window switch and re-check for the DTC: if the code clears, the switch or door-side wiring is likely the fault
Signal parameters
- Supply voltage (power feed) at door switch: ~12–14 V with ignition/accessory ON
- Switch output (signal) when idle: high-impedance/open or as specified by manufacturer; should NOT be tied to B+ when not commanded
- Measured resistance between switch signal terminal and battery positive when disconnected and not pressed: open/infinite (no continuity)
- If short-to-battery present: voltage at switch signal terminal will be ~12 V with respect to ground when it should be low or open
Diagnostic algorithm
- Connect a diagnostic scanner; read and record B1408 and any related codes; note conditions (key on, doors open, switch position).
- Perform a visual inspection of the driver door switch and the door harness at the hinge area for chafing, pin damage, corrosion, or evidence of water entry.
- With ignition ON, backprobe the switch connector: identify power (B+) and switch signal terminals using a wiring diagram. Verify power feed is present (~12–14 V).
- Measure voltage at the switch signal terminal with the switch disconnected. If the signal terminal measures ~12 V with switch disconnected, there is a short to positive in the harness or at a splice. If it measures near 0 V or open, the switch may be shorted internally.
- Disconnect the front left window switch and clear the DTC; attempt to operate windows or cycle the door/ignition and see if code returns. If the code stops, suspect the switch or door wiring downstream.
- If short remains with switch disconnected, isolate sections of the harness: measure continuity between the signal wire and battery positive; inspect and repair any shorted sections (focus on hinge flex area).
- If harness checks good and switch removed from circuit still shows no short, suspect door module/Body Control Module (BCM) input — verify with manufacturer diagnostic tests before replacing modules.
- After repair, reconnect components, clear stored codes, and perform functional test of the front left window; road test or cycle the door to ensure no reoccurrence.
- Safety note: when performing wiring repairs, disconnect the negative battery if required by the vehicle repair manual and follow electrostatic/disconnect procedures for control modules.
Likely causes
- Water ingress at the door switch connector or inside the switch causing short to B+
- Broken insulation where the switch signal conductor contacts a B+ feed in the door harness
- Failed switch contacts internally shorted to supply
- Loose or crushed wiring at the door hinge/bulkhead where harness flexes
Fault status
Status
Front left window UP (raise) switch circuit reports a short to positive (B+). The switch/signal conductor is receiving battery voltage when it should be open or low, indicating a shorted switch, damaged wiring, or connector fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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