Code
B1320
FIAT
B — Body
Driver door open circuit
Views:
UK: 3
EN: 6
RU: 9
AI status
Completed
Completed
100%
Causes
- Broken or worn driver door latch/microswitch
- Open, chafed, or corroded wiring in the driver door harness (common at door hinge/boot)
- Corroded or loose door connector or BCM connector pin
- Poor ground or failed pull-up resistor in BCM circuit
- Water intrusion into door latch or connectors
- Aftermarket alarm or accessory wiring interfering with the circuit
Symptoms
- Driver door ajar warning lamp or message
- Interior dome/map lights remain on or do not behave correctly
- Vehicle will not lock/arm or alarm false-triggers
- Battery drain if interior lights stay on
- DTC B1320 stored and possibly other body/comfort codes
- Door status incorrect on driver information display or scan tool
What to check
- Read live data with a scan tool: monitor driver door status while opening/closing the door
- Visual inspection of door harness, boot, and connectors for chafing, corrosion, or pin damage
- Wiggle test the wiring in the door boot while watching live data for intermittent changes
- Check continuity between the door switch pin and the BCM pin with harness disconnected
- Measure voltage at the switch connector (backprobe) with door open and closed
- Inspect and test the door latch switch for proper operation and resistance
Signal parameters
- Typical resting/open circuit: pulled up to battery voltage (approx. 10–14 V) if switch grounds when closed
- Typical closed switch: near 0–0.5 V (grounded) if the switch completes to ground
- Open-circuit/OL on continuity test between switch terminal and BCM indicates a wiring break
- Short to ground or battery can be detected as improper voltages at the BCM pin (0 V when it should be high or battery voltage when it should be low)
Diagnostic algorithm
- Connect an OBD-II/scan tool and read B1320 and any related codes. Record freeze-frame/live door status.
- Clear the code, cycle the driver door open/closed several times and see if the code returns or if the scan tool shows correct open/closed transitions.
- Visually inspect the driver door wiring harness, the rubber boot between door and body, and both connectors (door side and body side) for damage, corrosion or pin push-out. Repair any obvious damage.
- Backprobe the door switch connector. With ignition ON, observe voltage with the door open and closed. Expected: one state at battery voltage (open) and the other ~0 V (closed) depending on vehicle design.
- If voltage is incorrect or intermittent, perform a continuity test between the switch terminal and the BCM input pin with connectors removed. Loss of continuity indicates an open in the wiring—pay special attention to the hinge area.
- If wiring is continuous, test the door latch/switch directly: verify switch resistance/operation (closed ≈ near 0 Ω, open ≈ infinite). Replace latch assembly if switch fails.
- If switch and wiring check OK, inspect BCM connector for corrosion or bent pins and test for proper pull-up/pull-down voltages at the BCM pin. Repair or replace BCM only after excluding wiring/switch faults.
- Repair any damaged wiring (solder and heat-shrink or proper splice/replacement), replace faulty latch/switch, secure connectors and seal against moisture.
- After repairs, clear codes and verify proper operation over multiple cycles and road tests. Re-scan to confirm no recurrence.
Likely causes
- Damaged wiring at the door hinge (most common)
- Failed microswitch in driver door latch assembly
- Corroded/loose connector at door or BCM
- Water-damaged switch or connector
- Interference from aftermarket alarm wiring
Fault status
Status
Driver door open circuit — BCM detects an open or missing signal from the driver door switch/latch circuit indicating an open, short, or fault in the circuit.
Repair difficulty: Medium
Diagnostic time: 0.5 - 1.5 hours
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