Code
B1335
ALFA ROMEO
B — Body
Right rear door open circuit
Views:
UK: 5
EN: 7
RU: 3
AI status
Completed
Completed
100%
Causes
- Faulty or stuck right rear door latch/ajar switch
- Open, short-to-ground or short-to-battery in the door switch wiring (hinge/boot area)
- Corroded or loose connector at the door switch or body harness
- Water ingress or damage to switch or connector
- Faulty BCM or door module input circuit
- Aftermarket alarm/central-locking device altering the circuit
Symptoms
- Door ajar warning or lamp for right rear door on dash
- Interior lights or courtesy lamp staying on after door closed
- Central door locking or convenience features not working reliably for that door
- Possible battery drain if lamp stays on
- False alarm/door open alerts
What to check
- Retrieve codes and live data with a diagnostic scan tool; confirm B1335 is current or stored
- Operate and close the right rear door while watching the door-ajar live parameter
- Visually inspect door latch, switch and wiring harness through the hinge/boot area for damage or corrosion
- Check connector mating faces for corrosion, bent pins, or water intrusion
- Perform a wiggle test on harness while watching live data for intermittent changes
- Measure voltage at the switch connector with door open and closed, and perform continuity checks to BCM pin
Signal parameters
- Door ajar input is a digital switch signal. Typical behavior: closed door = logic low (near 0 V) or ground reference; open door = pulled to battery voltage (~9–12 V) depending on vehicle design
- Some vehicles use a pull-up resistor: expect ~0–1 V when closed and ~9–12 V when open
- Closed switch continuity: near 0 ohms between switch terminal and ground (vehicle-specific); open switch: infinite/very high resistance
- No fluctuation on a healthy circuit when the door is stationary
Diagnostic algorithm
- Connect a scan tool, confirm B1335 and view live data for the right rear door input while opening and closing the door.
- Visually inspect the door latch/switch area and wiring boot for damage, chafing, or moisture. Repair any obvious damage.
- With connector disconnected, inspect pins for corrosion or bent terminals. Clean and protect contacts if required.
- Backprobe the switch connector and measure voltage with door open and closed. Compare to expected digital switching behavior (see signal_params).
- Check continuity between the switch terminal and the BCM/door module input pin with harness stationary and while moving the door hinge (wiggle test) to reproduce any intermittent fault.
- If wiring and connector are good, bench-test or replace the door latch/switch assembly and recheck the circuit.
- If the switch and wiring check good but fault remains, verify BCM input operation. Inspect for aftermarket modules tied into door circuits. Replace or reprogram BCM only after ruling out wiring/switch faults.
- After repair, clear codes and confirm the fault does not return during normal operation and after road testing.
Likely causes
- Wiring stress/fatigue at the door hinge (most common)
- Corroded connector at the door jamb or inside door
- Failed door latch/position switch inside the lock assembly
- Intermittent contact caused by water/contamination
Fault status
Status
Right rear door open circuit — BCM detected an open or intermittent signal on the right rear door switch input. May cause door-ajar warnings, interior lamp on, or central locking issues.
Repair difficulty: Medium
Diagnostic time: 0.5 - 2.0 hours
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