Code
B1408
FIAT
B — Body
Front left electric window raising switch short to positive
Views:
UK: 4
EN: 6
RU: 9
AI status
Completed
Completed
100%
Causes
- Short in the switch harness to battery positive (chafed wiring contacting B+)
- Faulty/failed front left window switch with internal short
- Water ingress or corrosion in switch or connector causing conductive path to B+
- Incorrectly installed or swapped replacement switch/wiring
- Fault in body control module or wiring near the module (less common)
Symptoms
- Front left window will not operate (may be inoperative up or down)
- Intermittent or stuck window behavior
- Blown fuse(s) for window circuit or related circuits
- Related door/window switches may show faults or reduced function
- Stored fault B1408 in body/window control module
What to check
- Read and record stored DTCs with a scan tool; note freeze frame if available
- Visual inspection of front left door wiring, harness seals (rubber boot) and connectors for damage or corrosion
- Visually inspect the switch for signs of water ingress or melted plastic
- Check related fuses and relays for continuity and correct rating
- Measure voltage at the switch connector with ignition ON and with switch operated (see signal params)
- Check for continuity between the suspect switch wire and battery positive with ignition OFF (careful to isolate circuits)
Signal parameters
- Battery / supply voltage on switch power terminal: ~12 V with ignition ON
- Control/command lines should change state only when the switch is operated (no permanent +12 V when idle)
- With switch disconnected, there should be no continuity between the switch control pin and battery positive
- Motor current: low (near zero) when switch idle; high (several amps) only when motor commanded
- Resistance of a healthy switch contact: low ohms when closed, open/high when open
Diagnostic algorithm
- Read and clear codes, then attempt to reproduce. Confirm B1408 returns.
- Perform visual inspection of the front left door harness, door jamb, and rubber grommet for chafing, pinches, or water damage.
- With ignition OFF, disconnect the front left window switch connector. Check resistance/continuity between the suspect switch power/control pins and battery positive to confirm a short to B+. If continuity to B+ is present, isolate wiring to locate short.
- With ignition ON, measure voltage at the switch connector power and control pins. If a control pin shows permanent +12 V when it should be inactive, that indicates a short or a faulty switch/module.
- Bench-test the switch (disconnect from vehicle). Use a 12 V source and verify switch contacts change state only when actuated. Replace if internally shorted or contaminated.
- If wiring is suspected, perform back-probing and wiggle tests while monitoring voltage to find intermittent shorts (pay attention to door hinge area).
- If harness damage is found, repair or replace wiring and connectors. Use solder and heat shrink or proper crimp terminals; ensure grommet seals are intact.
- If switch and wiring test good, check the body/window control module outputs and grounds. Consider module replacement or repair only after wiring and switch eliminated as causes.
- After repairs, clear codes and verify proper operation of the window and that B1408 does not return.
- Safety note: take standard precautions when testing live circuits. Disconnect the battery before performing repairs on wiring or connectors; reconnect only for powered tests.
Likely causes
- Failed front left window switch
- Shorted or pinched wiring in door harness (rubber grommet area)
- Contaminated/corroded connector at switch or door junction
- Aftermarket repair or mis-wiring of switch
Fault status
Status
Front left electric window switch circuit: short to positive detected. Check switch, wiring, connectors and module for short to battery.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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