Code
B1320
ALFA ROMEO
B — Body
Driver door open circuit
Views:
UK: 5
EN: 5
RU: 9
AI status
Completed
Completed
100%
Causes
- Broken or shorted wiring in the driver door harness (common at hinge/boot)
- Corroded, loose or damaged connector/pins at door switch or BCM
- Failed door jamb/courtesy switch or door latch sensor
- Poor ground or power supply to the switch circuit
- Water intrusion or corrosion in door switch/connector
- Aftermarket alarm/remote wiring interfering with circuit
Symptoms
- Driver door ajar indicator lamp or message on dash
- Interior/reading lights remain on or do not behave correctly
- Central locking or alarm may not behave correctly for driver door
- Possible battery drain if lights remain on
- DTC B1320 stored and may be intermittent
What to check
- Check for stored freeze frame and confirmation count with OEM scan tool
- Visually inspect driver door harness through the boot for chafing, breaks or water entry
- Inspect and unplug the driver door switch/connector; look for corrosion or bent pins
- Perform a wiggle test of the door harness while watching the door-status input on a scan tool or multimeter
- Measure continuity between the door switch and the body control module pin with harness disconnected (use backprobe at BCM)
- Check for correct supply voltage and ground at the door switch connector
Signal parameters
- Typical closed-switch continuity: near 0 Ω (closed to ground) — actual depends on switch design
- Open-switch resistance: very high (kΩ to infinite) when open
- Voltage at switch pin with door open: may be near battery voltage or pulled-up to module reference (varies by vehicle)
- Voltage at switch pin with door closed: often near 0 V if switch grounds the line, or near reference if switch pulls to supply — verify with schematic
- Door-status on scan tool: binary open/closed (0/1) or percentage for some vehicles — should change state when switch actuated
Diagnostic algorithm
- Connect a compatible scan tool and confirm B1320 is present; note freeze frame and occurrence data
- Visually inspect the driver door area, door latch, switch and wiring boot for damage or moisture
- With connector disconnected, check continuity of the switch itself or resistance across switch terminals while operating the door latch/switch; replace switch if faulty
- Backprobe the harness at the body control module (or at an accessible module connector) and verify signal changes when operating the door switch
- If the switch is expected to ground the input, verify continuity to ground when closed (
- Perform a wiggle test of the door harness through full range of door motion while watching the scan tool for dropouts; repair any broken conductors in the boot
- Repair or replace damaged connectors/wiring (solder and heat-shrink or proper crimp repair), protect the harness and re-seal against moisture
- Clear code and test-drive; if code returns and wiring/switch is good, consider module input fault and consult manufacturer procedures before replacing BCM
Likely causes
- Broken wire in flex boot between body and door
- Connector pin pushed out, bent or corroded at door switch or module
- Door latch/switch mechanical failure or stuck actuator
- Moisture intrusion into door switch/connector causing intermittent open circuit
Fault status
Status
Stored B1320 — driver door open circuit detected by body control module. Fault may be intermittent or permanent until wiring or switch fault is repaired.
Repair difficulty: Medium
Diagnostic time: 0.5 - 2.0 hours
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