Code
B1345
FIAT
B — Body
Heated rear window switch input short to ground
Views:
UK: 4
EN: 4
RU: 3
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring harness making contact with chassis ground
- Corroded or bent connector pins at the switch or control module
- Failed or internally shorted heated rear window switch
- Aftermarket equipment or recent repairs that disturbed the wiring
- Faulty body control module (BCM) or internal input driver failure
Symptoms
- Heated rear window may not turn on or respond to switch
- Intermittent or no function of the defogger circuit
- Related body electrical warnings or multiple body codes stored
- Illumination/indicator lamp on switch may be dim, stuck on, or off
- Possible blown fuse if short current is high
What to check
- Read and record all stored codes and freeze-frame data with a scan tool
- Visually inspect switch, connector, and harness for damage, corrosion, or pin push-out
- Backprobe switch connector and measure voltage with ignition ON
- Disconnect the heated rear window switch and see if the code clears or changes
- Check for continuity between the signal wire and chassis ground (should not be continuous)
- Wiggle harness while observing live data or monitoring voltage to reproduce fault
Signal parameters
- With ignition ON, reference/feeding voltage at switch connector: typically battery voltage (~11–14 V) or module reference (often 5 V) depending on design — consult wiring diagram
- Short condition: signal wire near 0 V (ground) when it should be high or float
- Switch closed state: expected change from reference to ground or logic-level change — observe with scan tool or meter
- Resistance from signal wire to chassis ground should be high (kΩ to open); near 0 Ω indicates short
- Monitor for changes when actuating switch: live data should toggle per design
Diagnostic algorithm
- Use a scan tool to confirm B1345 and note any related codes and freeze frame data.
- Visually inspect switch, bezel, and wiring route behind dash and in trim for damage, corrosion, or pinching.
- Unplug the heated rear window switch. Clear codes, then cycle ignition and see if B1345 returns. If it does not, suspect switch or harness near switch.
- With connector unplugged, measure continuity between the switch signal pin and chassis ground. Near zero ohms indicates a short in the harness or connector.
- Backprobe the harness at the switch connector with ignition ON. Verify reference voltage and signal behavior when actuating the switch. Compare to expected values from service manual.
- If short is present with connector unplugged, trace the harness toward the BCM: inspect clips, grommets, door sills, and firewall for chafing. Disconnect intermediate connectors to isolate section with the short.
- If harness checks good, backprobe at the BCM input pin. If the short persists only at the module, suspect BCM internal fault.
- Repair or replace the damaged wiring or connector. If replacing switch, retest. If BCM replacement is required, verify all harness and connector integrity first.
- After repair, clear codes and test operation through multiple cycles and a short road/usage test to confirm repair.
Likely causes
- Short to ground in the switch harness between switch and BCM (most common)
- Contaminated/corroded switch connector causing low-resistance path to ground
- Switch itself internally shorted when removed or pressed
- Harness rubbed through near hinge, firewall or behind trim and contacting metal
- BCM input driver damaged (less common, after wiring checks)
Fault status
Status
Heated rear window switch input — short to ground detected (B1345)
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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