Code
B1399
ALFA ROMEO
B — Body
Front left full-open window relay open circuit
Views:
UK: 3
EN: 4
RU: 10
AI status
Completed
Completed
100%
Causes
- Open circuit in relay control or power wiring
- Faulty front left full-open relay
- Corroded or loose relay connector or pin
- Blown fuse or fusible link supplying the relay
- Poor or missing ground at relay or BCM
- Faulty BCM/window control driver
Symptoms
- Front left window will not move to the full-open (down) position on full-open command
- No audible relay click when commanding full-open
- Window may move normally in other directions or modes (partial up/down)
- Related window controls nonresponsive or intermittent at front left door
- DTC B1399 stored and lamp/message may be present
What to check
- Read and record stored DTCs and freeze frame data with a diagnostic scanner
- Visually inspect relay, fuse, connectors, and wiring for damage, corrosion, or water ingress
- Listen for relay click while commanding full-open from driver switch
- Check relevant fuses and fusible links for continuity
- Backprobe relay supply and control pins while operating the switch to confirm presence/absence of voltages
- Measure continuity between relay output terminal and front left window motor connector
Signal parameters
- Battery voltage (~12–14 V) present at relay power supply terminal with ignition/accessory on
- Control signal from BCM to relay coil: approximately battery voltage when activated and ~0 V when not active (may be switched to ground depending on design)
- Relay coil resistance (spec varies by relay; typically tens to a few hundred ohms — consult service manual)
- Continuity from relay output to front left window motor: low resistance when relay closed, open/infinite if circuit open
Diagnostic algorithm
- Verify and record B1399 and any associated codes with a scan tool
- Perform a visual inspection of the relay, relay socket, harness, and connectors for corrosion, damage, or water entry
- Check fuses/fusible links for the windows circuit; replace if blown and retest (note if fuse blows again, do not continue without diagnosing short)
- With ignition/accessory on, command front left full-open and listen for relay click; if click present, probe relay output for voltage to the window motor
- If no click, backprobe the control terminal of the relay while commanding full-open to verify the BCM is sending an activation signal (voltage or ground depending on design)
- Remove relay and measure coil resistance on the bench; compare to specification — replace relay if out of spec
- Check supply voltage at relay power terminal; if missing, trace supply back to fuse/IGN feed and repair as necessary
- Perform continuity check from relay output terminal to the front left window motor connector; repair any open or high-resistance wiring or connector issues
- If wiring and relay are good but no control signal from BCM, inspect BCM grounds and related circuits; consult wiring diagrams and consider BCM fault testing/reprogramming or replacement as a last resort
- Clear codes and verify proper operation by cycling the window and repeating the full-open command
Likely causes
- Defective front left full-open relay
- Broken or disconnected wire between BCM and relay coil or between relay output and window motor
- Corroded connector at relay or window switch
- Blown fuse protecting the window circuit
Fault status
Status
Front left full-open window relay circuit open
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
B1399
FIAT
B — Body
Front left full-open window relay open circuit
Views:
UK: 4
EN: 4
RU: 9
AI status
Completed
Completed
100%
Causes
- Open circuit in relay control or power wiring
- Faulty front left full-open relay
- Corroded or loose relay connector or pin
- Blown fuse or fusible link supplying the relay
- Poor or missing ground at relay or BCM
- Faulty BCM/window control driver
Symptoms
- Front left window will not move to the full-open (down) position on full-open command
- No audible relay click when commanding full-open
- Window may move normally in other directions or modes (partial up/down)
- Related window controls nonresponsive or intermittent at front left door
- DTC B1399 stored and lamp/message may be present
What to check
- Read and record stored DTCs and freeze frame data with a diagnostic scanner
- Visually inspect relay, fuse, connectors, and wiring for damage, corrosion, or water ingress
- Listen for relay click while commanding full-open from driver switch
- Check relevant fuses and fusible links for continuity
- Backprobe relay supply and control pins while operating the switch to confirm presence/absence of voltages
- Measure continuity between relay output terminal and front left window motor connector
Signal parameters
- Battery voltage (~12–14 V) present at relay power supply terminal with ignition/accessory on
- Control signal from BCM to relay coil: approximately battery voltage when activated and ~0 V when not active (may be switched to ground depending on design)
- Relay coil resistance (spec varies by relay; typically tens to a few hundred ohms — consult service manual)
- Continuity from relay output to front left window motor: low resistance when relay closed, open/infinite if circuit open
Diagnostic algorithm
- Verify and record B1399 and any associated codes with a scan tool
- Perform a visual inspection of the relay, relay socket, harness, and connectors for corrosion, damage, or water entry
- Check fuses/fusible links for the windows circuit; replace if blown and retest (note if fuse blows again, do not continue without diagnosing short)
- With ignition/accessory on, command front left full-open and listen for relay click; if click present, probe relay output for voltage to the window motor
- If no click, backprobe the control terminal of the relay while commanding full-open to verify the BCM is sending an activation signal (voltage or ground depending on design)
- Remove relay and measure coil resistance on the bench; compare to specification — replace relay if out of spec
- Check supply voltage at relay power terminal; if missing, trace supply back to fuse/IGN feed and repair as necessary
- Perform continuity check from relay output terminal to the front left window motor connector; repair any open or high-resistance wiring or connector issues
- If wiring and relay are good but no control signal from BCM, inspect BCM grounds and related circuits; consult wiring diagrams and consider BCM fault testing/reprogramming or replacement as a last resort
- Clear codes and verify proper operation by cycling the window and repeating the full-open command
Likely causes
- Defective front left full-open relay
- Broken or disconnected wire between BCM and relay coil or between relay output and window motor
- Corroded connector at relay or window switch
- Blown fuse protecting the window circuit
Fault status
Status
Front left full-open window relay circuit open
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
B1399
HUMMER
B — Body
Loss of KDD Communications
Views:
UK: 4
EN: 11
RU: 13
AI status
Completed
Completed
100%
Causes
- Open circuit in relay control or power wiring
- Faulty front left full-open relay
- Corroded or loose relay connector or pin
- Blown fuse or fusible link supplying the relay
- Poor or missing ground at relay or BCM
- Faulty BCM/window control driver
Symptoms
- Front left window will not move to the full-open (down) position on full-open command
- No audible relay click when commanding full-open
- Window may move normally in other directions or modes (partial up/down)
- Related window controls nonresponsive or intermittent at front left door
- DTC B1399 stored and lamp/message may be present
What to check
- Read and record stored DTCs and freeze frame data with a diagnostic scanner
- Visually inspect relay, fuse, connectors, and wiring for damage, corrosion, or water ingress
- Listen for relay click while commanding full-open from driver switch
- Check relevant fuses and fusible links for continuity
- Backprobe relay supply and control pins while operating the switch to confirm presence/absence of voltages
- Measure continuity between relay output terminal and front left window motor connector
Signal parameters
- Battery voltage (~12–14 V) present at relay power supply terminal with ignition/accessory on
- Control signal from BCM to relay coil: approximately battery voltage when activated and ~0 V when not active (may be switched to ground depending on design)
- Relay coil resistance (spec varies by relay; typically tens to a few hundred ohms — consult service manual)
- Continuity from relay output to front left window motor: low resistance when relay closed, open/infinite if circuit open
Diagnostic algorithm
- Verify and record B1399 and any associated codes with a scan tool
- Perform a visual inspection of the relay, relay socket, harness, and connectors for corrosion, damage, or water entry
- Check fuses/fusible links for the windows circuit; replace if blown and retest (note if fuse blows again, do not continue without diagnosing short)
- With ignition/accessory on, command front left full-open and listen for relay click; if click present, probe relay output for voltage to the window motor
- If no click, backprobe the control terminal of the relay while commanding full-open to verify the BCM is sending an activation signal (voltage or ground depending on design)
- Remove relay and measure coil resistance on the bench; compare to specification — replace relay if out of spec
- Check supply voltage at relay power terminal; if missing, trace supply back to fuse/IGN feed and repair as necessary
- Perform continuity check from relay output terminal to the front left window motor connector; repair any open or high-resistance wiring or connector issues
- If wiring and relay are good but no control signal from BCM, inspect BCM grounds and related circuits; consult wiring diagrams and consider BCM fault testing/reprogramming or replacement as a last resort
- Clear codes and verify proper operation by cycling the window and repeating the full-open command
Likely causes
- Defective front left full-open relay
- Broken or disconnected wire between BCM and relay coil or between relay output and window motor
- Corroded connector at relay or window switch
- Blown fuse protecting the window circuit
Fault status
Status
Front left full-open window relay circuit open
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
B1399
Other
B — Body
Driver Power Window One Touch Window Relay Circuit Open
Views:
UK: 19
EN: 28
RU: 30
AI status
Completed
Completed
100%
Causes
- Open circuit in relay control or power wiring
- Faulty front left full-open relay
- Corroded or loose relay connector or pin
- Blown fuse or fusible link supplying the relay
- Poor or missing ground at relay or BCM
- Faulty BCM/window control driver
Symptoms
- Front left window will not move to the full-open (down) position on full-open command
- No audible relay click when commanding full-open
- Window may move normally in other directions or modes (partial up/down)
- Related window controls nonresponsive or intermittent at front left door
- DTC B1399 stored and lamp/message may be present
What to check
- Read and record stored DTCs and freeze frame data with a diagnostic scanner
- Visually inspect relay, fuse, connectors, and wiring for damage, corrosion, or water ingress
- Listen for relay click while commanding full-open from driver switch
- Check relevant fuses and fusible links for continuity
- Backprobe relay supply and control pins while operating the switch to confirm presence/absence of voltages
- Measure continuity between relay output terminal and front left window motor connector
Signal parameters
- Battery voltage (~12–14 V) present at relay power supply terminal with ignition/accessory on
- Control signal from BCM to relay coil: approximately battery voltage when activated and ~0 V when not active (may be switched to ground depending on design)
- Relay coil resistance (spec varies by relay; typically tens to a few hundred ohms — consult service manual)
- Continuity from relay output to front left window motor: low resistance when relay closed, open/infinite if circuit open
Diagnostic algorithm
- Verify and record B1399 and any associated codes with a scan tool
- Perform a visual inspection of the relay, relay socket, harness, and connectors for corrosion, damage, or water entry
- Check fuses/fusible links for the windows circuit; replace if blown and retest (note if fuse blows again, do not continue without diagnosing short)
- With ignition/accessory on, command front left full-open and listen for relay click; if click present, probe relay output for voltage to the window motor
- If no click, backprobe the control terminal of the relay while commanding full-open to verify the BCM is sending an activation signal (voltage or ground depending on design)
- Remove relay and measure coil resistance on the bench; compare to specification — replace relay if out of spec
- Check supply voltage at relay power terminal; if missing, trace supply back to fuse/IGN feed and repair as necessary
- Perform continuity check from relay output terminal to the front left window motor connector; repair any open or high-resistance wiring or connector issues
- If wiring and relay are good but no control signal from BCM, inspect BCM grounds and related circuits; consult wiring diagrams and consider BCM fault testing/reprogramming or replacement as a last resort
- Clear codes and verify proper operation by cycling the window and repeating the full-open command
Likely causes
- Defective front left full-open relay
- Broken or disconnected wire between BCM and relay coil or between relay output and window motor
- Corroded connector at relay or window switch
- Blown fuse protecting the window circuit
Fault status
Status
Front left full-open window relay circuit open
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email