B1399

Code

FIAT B — Body

Front left full-open window relay open circuit

Brand: FIAT

Type: B — Body

Views: UK: 19 EN: 28 RU: 25

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Page language: EN

Blown fuse for power window circuit
Failed front-left full-open window relay (open coil or contacts)
Open or damaged wiring between relay and body control module (BCM) or power source
Poor or corroded connector or ground at relay socket
Faulty window switch or BCM driver output (open circuit)
Intermittent connection or terminal pushed out of connector

Front-left window will not open fully (no full-open function) or will not move on the full-open command
No audible click from relay when full-open command is given
Other windows may operate normally
Possible warning or message on vehicle cluster related to window operation

Scan vehicle for stored codes and freeze frame data; note any related window or BCM codes
Visually inspect fuse(s) and relay(s) in power distribution and body modules for damage or corrosion
Check for relay click when commanding full-open; if none, test relay coil power and ground at socket
Measure battery voltage at relay power terminal and at relay contact output when commanded
Perform continuity check between relay socket pins and BCM/switch wiring according to wiring diagram
Inspect and wiggle connectors and wiring harness for intermittent faults

Relay coil supply: ~12 V (battery voltage) present at coil feed terminal with key on
Relay coil control: ground (or +12 V depending on design) from BCM when full-open commanded
Coil resistance: manufacturer spec (typical 50-150 ohms for small relays) — compare to known-good relay
Contact output: battery voltage present at relay output terminal when relay is energized
No continuity between coil terminals indicates open relay coil

Safety: Park vehicle, key off, remove ignition key. Use PPE and battery disconnect procedures if soldering or harness repair is required.
Confirm complaint: Try full-open window function while monitoring for relay click or response.
Scan: Retrieve and record DTCs and freeze frame. Clear codes then re-test to see if code returns.
Visual inspection: Check fuses, relay, fusebox and connector condition for corrosion, heat damage or loose terminals.
Relay bench test: Remove relay and test coil resistance and contact switching on a bench with 12 V supply. Replace relay if coil open or contacts fail.
Power/ground verification: With relay installed, backprobe relay socket to verify constant battery feed to relay power pin and proper control signal (ground or +12 V) from BCM when commanded.
Continuity and harness testing: If feed or control is missing, trace and measure continuity between relay socket and BCM/switch, repair any open wires or terminals found.
Check BCM output: If wiring and relay are good but control signal is absent, test BCM driver output per service manual; consider module programming/repair if faulty.
Repair and retest: Replace faulty relay, repair wiring, tighten/replace connectors or replace fuse as required. Reclear DTCs and verify window full-open operation and that code does not return.
If intermittent: Perform wiggle tests while operating the window to reproduce fault and identify broken conductors or poor terminals.

⚠️ Status

Front-left full-open window relay open circuit detected. Check relay, fuse, wiring, connectors and BCM control output.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-1.5 hours

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