Code
B1345
ALFA ROMEO
B — Body
Heated rear window switch input short to ground
Views:
UK: 4
EN: 6
RU: 3
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring shorted to chassis ground
- Faulty heated rear window switch (internal short)
- Corroded or loose connector at switch or BCM
- Water ingress or debris causing a short at the switch
- Aftermarket accessory or modification incorrectly wired
- Faulty BCM/input driver (less common)
Symptoms
- Rear window defogger does not activate
- Defogger indicator lamp does not illuminate or behaves intermittently
- Defogger may operate only intermittently or stuck off
- Possible blown fuse for defogger circuit
- Diagnostic trouble code B1345 stored in BCM
What to check
- Read and record DTCs and freeze-frame data with a diagnostic scanner
- Visually inspect switch, connector, and wiring for damage, corrosion, or moisture
- Check related fuses and relays for continuity and correct operation
- Backprobe switch connector with ignition ON and observe signal voltage while operating switch
- Measure continuity/resistance between switch input wire and chassis ground with connector disconnected
- Inspect for aftermarket wiring or splices in the rear window/defogger circuit
Signal parameters
- With ignition ON and switch in the OFF position: switch input typically at pull-up voltage (~battery voltage, ~11–14 V) depending on design
- With switch activated (depending on design): input may be pulled to ground (~0 V) to signal activation
- Resistance of a closed switch often near 0 Ω between its switched terminals; open switch shows very high/OL
- Continuity to chassis ground on the switch input wire with connector disconnected should read OL (no continuity) unless the switch is commanded to ground
Diagnostic algorithm
- Connect a capable diagnostic scanner. Read and record stored codes and any related UID or freeze-frame data.
- Visually inspect the rear window switch, bezel, and harness for physical damage, corrosion, or moisture. Remove switch from panel if necessary.
- Check fuses and relays for the defogger/heated rear window circuit; replace any blown fuses and retest.
- With ignition ON, backprobe the switch connector. Observe the signal/wiring voltage with switch OFF and ON. Note whether the input is always at or near 0 V (indicates short to ground).
- Disconnect the switch from the harness. Measure resistance/continuity between the switch input wire (harness side) and chassis ground. If there is continuity to ground with switch disconnected, trace wiring for a short to chassis.
- If harness shows short, visually and physically trace harness routing, looking for chafing at body openings, connectors, or contact points. Repair damaged insulation and replace or splice wiring as required.
- If harness is open/clean but short appears at the switch, bench-test or replace the switch and recheck circuit.
- If wiring and switch check good, test the BCM input: check for correct pull-up reference voltage at the BCM connector and inspect BCM grounds. Replace BCM only after confirming wiring/switch faults are resolved.
- Clear codes and perform functional test of rear window defogger. Re-scan after test to confirm no recurrence.
Likely causes
- Wiring harness chafed where it passes through body panels, contacting ground
- Switch contacts internally shorted or short to ground at switch housing
- Connector pins corroded, bent or pushed out allowing grounding
- Water or condensation has entered the switch assembly
- Previous repair or splice created an unintended ground connection
Fault status
Status
Heated rear window switch input short to ground detected by Body Control Module — circuit voltage lower than expected. Fault stored; rear window heater may not operate correctly.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
B1345
FIAT
B — Body
Heated rear window switch input short to ground
Views:
UK: 5
EN: 4
RU: 3
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring shorted to chassis ground
- Faulty heated rear window switch (internal short)
- Corroded or loose connector at switch or BCM
- Water ingress or debris causing a short at the switch
- Aftermarket accessory or modification incorrectly wired
- Faulty BCM/input driver (less common)
Symptoms
- Rear window defogger does not activate
- Defogger indicator lamp does not illuminate or behaves intermittently
- Defogger may operate only intermittently or stuck off
- Possible blown fuse for defogger circuit
- Diagnostic trouble code B1345 stored in BCM
What to check
- Read and record DTCs and freeze-frame data with a diagnostic scanner
- Visually inspect switch, connector, and wiring for damage, corrosion, or moisture
- Check related fuses and relays for continuity and correct operation
- Backprobe switch connector with ignition ON and observe signal voltage while operating switch
- Measure continuity/resistance between switch input wire and chassis ground with connector disconnected
- Inspect for aftermarket wiring or splices in the rear window/defogger circuit
Signal parameters
- With ignition ON and switch in the OFF position: switch input typically at pull-up voltage (~battery voltage, ~11–14 V) depending on design
- With switch activated (depending on design): input may be pulled to ground (~0 V) to signal activation
- Resistance of a closed switch often near 0 Ω between its switched terminals; open switch shows very high/OL
- Continuity to chassis ground on the switch input wire with connector disconnected should read OL (no continuity) unless the switch is commanded to ground
Diagnostic algorithm
- Connect a capable diagnostic scanner. Read and record stored codes and any related UID or freeze-frame data.
- Visually inspect the rear window switch, bezel, and harness for physical damage, corrosion, or moisture. Remove switch from panel if necessary.
- Check fuses and relays for the defogger/heated rear window circuit; replace any blown fuses and retest.
- With ignition ON, backprobe the switch connector. Observe the signal/wiring voltage with switch OFF and ON. Note whether the input is always at or near 0 V (indicates short to ground).
- Disconnect the switch from the harness. Measure resistance/continuity between the switch input wire (harness side) and chassis ground. If there is continuity to ground with switch disconnected, trace wiring for a short to chassis.
- If harness shows short, visually and physically trace harness routing, looking for chafing at body openings, connectors, or contact points. Repair damaged insulation and replace or splice wiring as required.
- If harness is open/clean but short appears at the switch, bench-test or replace the switch and recheck circuit.
- If wiring and switch check good, test the BCM input: check for correct pull-up reference voltage at the BCM connector and inspect BCM grounds. Replace BCM only after confirming wiring/switch faults are resolved.
- Clear codes and perform functional test of rear window defogger. Re-scan after test to confirm no recurrence.
Likely causes
- Wiring harness chafed where it passes through body panels, contacting ground
- Switch contacts internally shorted or short to ground at switch housing
- Connector pins corroded, bent or pushed out allowing grounding
- Water or condensation has entered the switch assembly
- Previous repair or splice created an unintended ground connection
Fault status
Status
Heated rear window switch input short to ground detected by Body Control Module — circuit voltage lower than expected. Fault stored; rear window heater may not operate correctly.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
B1345
Other
B — Body
Heated Backlite Input Circuit Short To Ground
Views:
UK: 13
EN: 25
RU: 20
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring shorted to chassis ground
- Faulty heated rear window switch (internal short)
- Corroded or loose connector at switch or BCM
- Water ingress or debris causing a short at the switch
- Aftermarket accessory or modification incorrectly wired
- Faulty BCM/input driver (less common)
Symptoms
- Rear window defogger does not activate
- Defogger indicator lamp does not illuminate or behaves intermittently
- Defogger may operate only intermittently or stuck off
- Possible blown fuse for defogger circuit
- Diagnostic trouble code B1345 stored in BCM
What to check
- Read and record DTCs and freeze-frame data with a diagnostic scanner
- Visually inspect switch, connector, and wiring for damage, corrosion, or moisture
- Check related fuses and relays for continuity and correct operation
- Backprobe switch connector with ignition ON and observe signal voltage while operating switch
- Measure continuity/resistance between switch input wire and chassis ground with connector disconnected
- Inspect for aftermarket wiring or splices in the rear window/defogger circuit
Signal parameters
- With ignition ON and switch in the OFF position: switch input typically at pull-up voltage (~battery voltage, ~11–14 V) depending on design
- With switch activated (depending on design): input may be pulled to ground (~0 V) to signal activation
- Resistance of a closed switch often near 0 Ω between its switched terminals; open switch shows very high/OL
- Continuity to chassis ground on the switch input wire with connector disconnected should read OL (no continuity) unless the switch is commanded to ground
Diagnostic algorithm
- Connect a capable diagnostic scanner. Read and record stored codes and any related UID or freeze-frame data.
- Visually inspect the rear window switch, bezel, and harness for physical damage, corrosion, or moisture. Remove switch from panel if necessary.
- Check fuses and relays for the defogger/heated rear window circuit; replace any blown fuses and retest.
- With ignition ON, backprobe the switch connector. Observe the signal/wiring voltage with switch OFF and ON. Note whether the input is always at or near 0 V (indicates short to ground).
- Disconnect the switch from the harness. Measure resistance/continuity between the switch input wire (harness side) and chassis ground. If there is continuity to ground with switch disconnected, trace wiring for a short to chassis.
- If harness shows short, visually and physically trace harness routing, looking for chafing at body openings, connectors, or contact points. Repair damaged insulation and replace or splice wiring as required.
- If harness is open/clean but short appears at the switch, bench-test or replace the switch and recheck circuit.
- If wiring and switch check good, test the BCM input: check for correct pull-up reference voltage at the BCM connector and inspect BCM grounds. Replace BCM only after confirming wiring/switch faults are resolved.
- Clear codes and perform functional test of rear window defogger. Re-scan after test to confirm no recurrence.
Likely causes
- Wiring harness chafed where it passes through body panels, contacting ground
- Switch contacts internally shorted or short to ground at switch housing
- Connector pins corroded, bent or pushed out allowing grounding
- Water or condensation has entered the switch assembly
- Previous repair or splice created an unintended ground connection
Fault status
Status
Heated rear window switch input short to ground detected by Body Control Module — circuit voltage lower than expected. Fault stored; rear window heater may not operate correctly.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
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0
Send to email