Code
B1343
ALFA ROMEO
B — Body
Heated rear window input circuit
Views:
UK: 3
EN: 3
RU: 1
AI status
Completed
Completed
100%
Causes
- Open or short in heated rear window wiring (supply, switch loop, or ground)
- Corroded or loose connector at rear window, switch, relay or BCM
- Blown fuse or faulty relay in heater/defogger circuit
- Faulty rear window switch or indicator lamp
- High resistance in heated grid or poor ground at window
- Water ingress or corrosion at rear window harness or connector
Symptoms
- Rear window defogger/heater does not turn on
- Defogger indicator lamp on dash or switch does not illuminate or is intermittent
- Defogger works intermittently or only in certain conditions
- Related HVAC or body electrical features may show errors or limited function
- Scan tool reports B1343 stored and possibly other related body codes
What to check
- Retrieve freeze frame and full DTC list with a diagnostic scanner; note conditions when code set
- Visually inspect fuses and relays for the rear window heater circuit; swap relay if suspected
- Inspect wiring and connectors at the rear window, switch, relay, and BCM for corrosion, damage or loose pins
- Operate the switch while monitoring terminal voltages at switch, relay and BCM connector
- Check continuity and resistance of heated rear window grid leads (with battery disconnected) and verify ground
- Perform wiggle tests on harnesses while observing scan tool data for input changes
Signal parameters
- Battery supply on heater circuit: ≈ 12–14 V with ignition ON and defogger switched ON
- Switch/BCM input logic: ~0 V (low) when off, battery voltage (~12 V) or TTL high when on depending on vehicle design
- Relay coil supply: battery voltage on one side, switched ground or logic signal on the other when activated
- Heated grid continuity: low resistance path (typical: single-digit to low double-digit ohms per manufacturer — compare to spec)
- Ground: close to 0 Ω continuity to chassis ground
Diagnostic algorithm
- Connect a diagnostic scan tool, read all body module codes and freeze frame data. Note ignition key position and temperature conditions.
- Visually inspect fuses and relays for the heated rear window circuit. Replace any suspect components and recheck.
- Inspect connectors and harnesses at the rear window, switch, relay and BCM for corrosion, water ingress, broken wires or pushed-out pins. Repair as needed.
- With a multimeter, verify battery voltage present at the fused input to the defogger circuit and at the relay supply terminal with ignition ON.
- Operate the defogger switch while measuring the switch output and the BCM input pin to verify the correct logic change (0 V ↔ battery voltage).
- Check relay activation: verify coil voltage and that relay contacts pass battery voltage to the rear window when energized. Replace relay if contacts fail.
- With battery disconnected, measure continuity and resistance across the heated grid terminals to confirm no open circuit and compare to specification. Also check continuity to ground where applicable.
- Perform wiggle/stress tests on harnesses and connectors while monitoring the BCM input with the scanner to reproduce intermittent faults.
- If wiring, connectors, switch, relay and grid check good, consider BCM input circuit testing per manufacturer service manual (pin-level checks) or reflashing/replacing BCM if confirmed faulty.
- After repairs, clear DTCs and verify repair by repeated activation and road/ambient condition checks as needed.
Likely causes
- Blown fuse or failed relay supplying the rear window heater
- Poor connector or wiring fault between the switch and BCM or between BCM and rear window
- Faulty rear window switch (open/short contacts or broken illumination)
- Corroded ground or high resistance in the heated grid connection
- BCM input fault (less common) or software anomaly
Fault status
Status
Heated rear window input circuit — BCM detected abnormal input (open/short/intermittent/power/ground fault).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
B1343
FIAT
B — Body
Heated rear window input circuit
Views:
UK: 3
EN: 5
RU: 2
AI status
Completed
Completed
100%
Causes
- Open or short in heated rear window wiring (supply, switch loop, or ground)
- Corroded or loose connector at rear window, switch, relay or BCM
- Blown fuse or faulty relay in heater/defogger circuit
- Faulty rear window switch or indicator lamp
- High resistance in heated grid or poor ground at window
- Water ingress or corrosion at rear window harness or connector
Symptoms
- Rear window defogger/heater does not turn on
- Defogger indicator lamp on dash or switch does not illuminate or is intermittent
- Defogger works intermittently or only in certain conditions
- Related HVAC or body electrical features may show errors or limited function
- Scan tool reports B1343 stored and possibly other related body codes
What to check
- Retrieve freeze frame and full DTC list with a diagnostic scanner; note conditions when code set
- Visually inspect fuses and relays for the rear window heater circuit; swap relay if suspected
- Inspect wiring and connectors at the rear window, switch, relay, and BCM for corrosion, damage or loose pins
- Operate the switch while monitoring terminal voltages at switch, relay and BCM connector
- Check continuity and resistance of heated rear window grid leads (with battery disconnected) and verify ground
- Perform wiggle tests on harnesses while observing scan tool data for input changes
Signal parameters
- Battery supply on heater circuit: ≈ 12–14 V with ignition ON and defogger switched ON
- Switch/BCM input logic: ~0 V (low) when off, battery voltage (~12 V) or TTL high when on depending on vehicle design
- Relay coil supply: battery voltage on one side, switched ground or logic signal on the other when activated
- Heated grid continuity: low resistance path (typical: single-digit to low double-digit ohms per manufacturer — compare to spec)
- Ground: close to 0 Ω continuity to chassis ground
Diagnostic algorithm
- Connect a diagnostic scan tool, read all body module codes and freeze frame data. Note ignition key position and temperature conditions.
- Visually inspect fuses and relays for the heated rear window circuit. Replace any suspect components and recheck.
- Inspect connectors and harnesses at the rear window, switch, relay and BCM for corrosion, water ingress, broken wires or pushed-out pins. Repair as needed.
- With a multimeter, verify battery voltage present at the fused input to the defogger circuit and at the relay supply terminal with ignition ON.
- Operate the defogger switch while measuring the switch output and the BCM input pin to verify the correct logic change (0 V ↔ battery voltage).
- Check relay activation: verify coil voltage and that relay contacts pass battery voltage to the rear window when energized. Replace relay if contacts fail.
- With battery disconnected, measure continuity and resistance across the heated grid terminals to confirm no open circuit and compare to specification. Also check continuity to ground where applicable.
- Perform wiggle/stress tests on harnesses and connectors while monitoring the BCM input with the scanner to reproduce intermittent faults.
- If wiring, connectors, switch, relay and grid check good, consider BCM input circuit testing per manufacturer service manual (pin-level checks) or reflashing/replacing BCM if confirmed faulty.
- After repairs, clear DTCs and verify repair by repeated activation and road/ambient condition checks as needed.
Likely causes
- Blown fuse or failed relay supplying the rear window heater
- Poor connector or wiring fault between the switch and BCM or between BCM and rear window
- Faulty rear window switch (open/short contacts or broken illumination)
- Corroded ground or high resistance in the heated grid connection
- BCM input fault (less common) or software anomaly
Fault status
Status
Heated rear window input circuit — BCM detected abnormal input (open/short/intermittent/power/ground fault).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
B1343
HUMMER
B — Body
Air Inlet Door Movement Fault
Views:
UK: 4
EN: 12
RU: 4
AI status
Completed
Completed
100%
Causes
- Open or short in heated rear window wiring (supply, switch loop, or ground)
- Corroded or loose connector at rear window, switch, relay or BCM
- Blown fuse or faulty relay in heater/defogger circuit
- Faulty rear window switch or indicator lamp
- High resistance in heated grid or poor ground at window
- Water ingress or corrosion at rear window harness or connector
Symptoms
- Rear window defogger/heater does not turn on
- Defogger indicator lamp on dash or switch does not illuminate or is intermittent
- Defogger works intermittently or only in certain conditions
- Related HVAC or body electrical features may show errors or limited function
- Scan tool reports B1343 stored and possibly other related body codes
What to check
- Retrieve freeze frame and full DTC list with a diagnostic scanner; note conditions when code set
- Visually inspect fuses and relays for the rear window heater circuit; swap relay if suspected
- Inspect wiring and connectors at the rear window, switch, relay, and BCM for corrosion, damage or loose pins
- Operate the switch while monitoring terminal voltages at switch, relay and BCM connector
- Check continuity and resistance of heated rear window grid leads (with battery disconnected) and verify ground
- Perform wiggle tests on harnesses while observing scan tool data for input changes
Signal parameters
- Battery supply on heater circuit: ≈ 12–14 V with ignition ON and defogger switched ON
- Switch/BCM input logic: ~0 V (low) when off, battery voltage (~12 V) or TTL high when on depending on vehicle design
- Relay coil supply: battery voltage on one side, switched ground or logic signal on the other when activated
- Heated grid continuity: low resistance path (typical: single-digit to low double-digit ohms per manufacturer — compare to spec)
- Ground: close to 0 Ω continuity to chassis ground
Diagnostic algorithm
- Connect a diagnostic scan tool, read all body module codes and freeze frame data. Note ignition key position and temperature conditions.
- Visually inspect fuses and relays for the heated rear window circuit. Replace any suspect components and recheck.
- Inspect connectors and harnesses at the rear window, switch, relay and BCM for corrosion, water ingress, broken wires or pushed-out pins. Repair as needed.
- With a multimeter, verify battery voltage present at the fused input to the defogger circuit and at the relay supply terminal with ignition ON.
- Operate the defogger switch while measuring the switch output and the BCM input pin to verify the correct logic change (0 V ↔ battery voltage).
- Check relay activation: verify coil voltage and that relay contacts pass battery voltage to the rear window when energized. Replace relay if contacts fail.
- With battery disconnected, measure continuity and resistance across the heated grid terminals to confirm no open circuit and compare to specification. Also check continuity to ground where applicable.
- Perform wiggle/stress tests on harnesses and connectors while monitoring the BCM input with the scanner to reproduce intermittent faults.
- If wiring, connectors, switch, relay and grid check good, consider BCM input circuit testing per manufacturer service manual (pin-level checks) or reflashing/replacing BCM if confirmed faulty.
- After repairs, clear DTCs and verify repair by repeated activation and road/ambient condition checks as needed.
Likely causes
- Blown fuse or failed relay supplying the rear window heater
- Poor connector or wiring fault between the switch and BCM or between BCM and rear window
- Faulty rear window switch (open/short contacts or broken illumination)
- Corroded ground or high resistance in the heated grid connection
- BCM input fault (less common) or software anomaly
Fault status
Status
Heated rear window input circuit — BCM detected abnormal input (open/short/intermittent/power/ground fault).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
B1343
Other
B — Body
Heated Backlite Input Circuit Failure
Views:
UK: 22
EN: 33
RU: 26
AI status
Completed
Completed
100%
Causes
- Open or short in heated rear window wiring (supply, switch loop, or ground)
- Corroded or loose connector at rear window, switch, relay or BCM
- Blown fuse or faulty relay in heater/defogger circuit
- Faulty rear window switch or indicator lamp
- High resistance in heated grid or poor ground at window
- Water ingress or corrosion at rear window harness or connector
Symptoms
- Rear window defogger/heater does not turn on
- Defogger indicator lamp on dash or switch does not illuminate or is intermittent
- Defogger works intermittently or only in certain conditions
- Related HVAC or body electrical features may show errors or limited function
- Scan tool reports B1343 stored and possibly other related body codes
What to check
- Retrieve freeze frame and full DTC list with a diagnostic scanner; note conditions when code set
- Visually inspect fuses and relays for the rear window heater circuit; swap relay if suspected
- Inspect wiring and connectors at the rear window, switch, relay, and BCM for corrosion, damage or loose pins
- Operate the switch while monitoring terminal voltages at switch, relay and BCM connector
- Check continuity and resistance of heated rear window grid leads (with battery disconnected) and verify ground
- Perform wiggle tests on harnesses while observing scan tool data for input changes
Signal parameters
- Battery supply on heater circuit: ≈ 12–14 V with ignition ON and defogger switched ON
- Switch/BCM input logic: ~0 V (low) when off, battery voltage (~12 V) or TTL high when on depending on vehicle design
- Relay coil supply: battery voltage on one side, switched ground or logic signal on the other when activated
- Heated grid continuity: low resistance path (typical: single-digit to low double-digit ohms per manufacturer — compare to spec)
- Ground: close to 0 Ω continuity to chassis ground
Diagnostic algorithm
- Connect a diagnostic scan tool, read all body module codes and freeze frame data. Note ignition key position and temperature conditions.
- Visually inspect fuses and relays for the heated rear window circuit. Replace any suspect components and recheck.
- Inspect connectors and harnesses at the rear window, switch, relay and BCM for corrosion, water ingress, broken wires or pushed-out pins. Repair as needed.
- With a multimeter, verify battery voltage present at the fused input to the defogger circuit and at the relay supply terminal with ignition ON.
- Operate the defogger switch while measuring the switch output and the BCM input pin to verify the correct logic change (0 V ↔ battery voltage).
- Check relay activation: verify coil voltage and that relay contacts pass battery voltage to the rear window when energized. Replace relay if contacts fail.
- With battery disconnected, measure continuity and resistance across the heated grid terminals to confirm no open circuit and compare to specification. Also check continuity to ground where applicable.
- Perform wiggle/stress tests on harnesses and connectors while monitoring the BCM input with the scanner to reproduce intermittent faults.
- If wiring, connectors, switch, relay and grid check good, consider BCM input circuit testing per manufacturer service manual (pin-level checks) or reflashing/replacing BCM if confirmed faulty.
- After repairs, clear DTCs and verify repair by repeated activation and road/ambient condition checks as needed.
Likely causes
- Blown fuse or failed relay supplying the rear window heater
- Poor connector or wiring fault between the switch and BCM or between BCM and rear window
- Faulty rear window switch (open/short contacts or broken illumination)
- Corroded ground or high resistance in the heated grid connection
- BCM input fault (less common) or software anomaly
Fault status
Status
Heated rear window input circuit — BCM detected abnormal input (open/short/intermittent/power/ground fault).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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