Code
B1505
ALFA ROMEO
B — Body
Right turn indicator warning lamp short to positive
Views:
UK: 5
EN: 21
RU: 3
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring harness causing contact with battery positive
- Corroded or pushed-back connector pins at the lamp or BCM
- Failed indicator bulb or LED module with internal short
- Faulty body control module / instrument cluster driver output
- Aftermarket accessory or trailer wiring incorrectly connected and feeding battery voltage into the circuit
- Blown or incorrectly rated fuse, relay or protective device failed to operate
Symptoms
- Right turn indicator warning lamp on dash may be permanently illuminated
- Turn signal may not flash or may flash abnormal (fast/slow/one side inoperative)
- Possible warning message or lamp on cluster related to indicator circuit
- Blown interior fuses or intermittent operation of right turn indicators
What to check
- Read and record freeze frame data and fault history with a diagnostic tool supporting Alfa Romeo manufacturer codes
- Visually inspect right front/rear lamp assembly, socket and harness for damage, corrosion, melted insulation or aftermarket splices
- Check connectors at the lamp and at the BCM/cluster for bent pins, corrosion, or pushed-out terminals
- Measure DC voltage at the lamp socket with ignition ON and both with turn signal OFF and with right-turn signal requested
- Check for continuity between lamp socket negative/return and BCM output pin with ignition off (verify no short to battery positive)
- Disconnect the right indicator lamp and re-check for fault to see if code clears or changes
Signal parameters
- Lamp circuit expected voltage (turn signal OFF): approximately 0 V (or near chassis ground) on the lamp return/driver pin
- Lamp circuit expected voltage (turn signal ON): pulsed approx. vehicle battery voltage (~12 V) at blink frequency (typical 1–2 Hz)
- If LED module present: driver output may be PWM; expect pulsed output rather than steady 12 V
- Current draw: typical incandescent indicator bulbs draw under a few amps; an unexpected steady battery voltage when circuit should be low indicates a short to positive
- Resistance: open circuit when bulb removed; continuity to BCM pin when connector attached (verify with wiring diagram)
Diagnostic algorithm
- Connect a diagnostic scanner and confirm B1505 is current or historic. Note freeze-frame conditions and any accompanying codes.
- Perform a visual inspection of the right indicator lamp assembly, socket, wiring harness routing and connectors for physical damage, corrosion or water ingress.
- With ignition ON, backprobe the lamp connector: measure voltage on the indicator driver/return pin with turn signal OFF (should be near 0 V). If it shows battery voltage, suspect a short to positive.
- Operate the right turn signal and observe voltage waveform: it should be a pulsed (on/off) voltage. If the circuit is stuck at battery voltage or abnormal, disconnect the lamp connector and repeat. If the fault clears when disconnected, the lamp or its harness is likely the cause.
- If disconnecting the lamp does not clear the condition, trace wiring toward the BCM using wiring diagrams. Look for chafe points, aftermarket splices, or accessory connections that could feed battery positive into the circuit.
- Check connector pins and ground integrity at both ends. Repair or replace corroded pins, re-seat terminals and apply dielectric grease where appropriate.
- If wiring and lamp appear good, test the BCM/cluster output by comparing to a known-good channel or bench test the module per manufacturer procedures. Replace BCM/cluster only after eliminating wiring and lamp faults.
- After repairs, clear codes and perform a road test/indicator cycle to confirm proper operation and that B1505 does not return.
Likely causes
- Wiring short to fused ignition/battery feed near the right indicator or lamp socket
- Corroded lamp socket or connector allowing positive feed to contact lamp return
- Shorted LED indicator module (if vehicle uses LED instead of filament bulbs)
- Poor repair/previous bodywork where wiring was pinched
Fault status
Status
Stored fault: Right turn indicator warning lamp circuit short to positive (battery voltage detected on lamp driver when it should be low). Fault may be active or stored; BCM has flagged a short-to-positive condition on the right indicator lamp circuit.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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