Code
B1348
ALFA ROMEO
B — Body
Heated rear window relay open circuit
Views:
UK: 1
EN: 4
RU: 2
AI status
Completed
Completed
100%
Causes
- Blown fuse for the rear window heater or relay coil circuit
- Defective rear window/heater relay (open internal coil or contact)
- Damaged, corroded or disconnected wiring or connectors in relay control or power feed
- Poor or missing ground at relay or rear window heater
- Faulty body control module / relay driver output
- Failed rear window heating grid (open circuit in the grid) or connector fault
Symptoms
- Heated rear window does not turn on
- Rear window heater indicator lamp may not illuminate
- No clicking sound from relay when the heater switch is operated
- Diagnostic trouble code B1348 stored in the body control module
What to check
- Verify accessory/battery voltage at the relay power terminal with ignition on
- Check for fuse continuity for the rear window heater and related circuits
- Listen for relay click when defogger is commanded; if absent, check coil control voltage
- Inspect relay and socket for corrosion, burning, or loose terminals
- Measure continuity between relay output and rear window heater connector
- Scan modules for additional related DTCs and relevant freeze frame data
Signal parameters
- Battery voltage at relay supply terminal: ~12–14 V when ignition/accessory power is on
- Relay coil control: either battery voltage or ground drive depending on chassis design; active state should change coil terminal to near 0 V (ground‑switch) or near battery voltage (positive‑switch)
- Typical relay coil resistance: ~50–200 ohms (coil current ≈ 60–240 mA) — varies by relay
- Closed relay contact voltage drop:
- Rear window heater current draw: typically several amps (commonly 5–20 A depending on vehicle); open circuit will show very low or infinite resistance at the heater connector
Diagnostic algorithm
- Read and record freeze frame data and any other stored DTCs with an OBD scanner.
- Visually inspect relay, relay socket, related fuses, and wiring for obvious damage, corrosion, or loose connections.
- Check fuse(s) for continuity and replace if blown. Retest function.
- With ignition on, measure battery voltage at the relay power terminal. If no power, trace upstream fuse/junction for loss of supply.
- Command the rear window heater on while monitoring the relay coil terminals: verify the control terminal changes state (to ground or to +12 V depending on design). If control signal is present but relay does not click, substitute a known-good relay and retest.
- If relay clicks but heater still inoperative, measure voltage at the relay output terminal while activated. If voltage is present at relay output but not at the rear window connector, perform continuity check of harness between relay and heater.
- Measure resistance of the rear window heating grid (with power removed). Infinite or very high resistance indicates an open grid or broken connector.
- Check ground continuity from the heater ground to chassis; repair any poor grounds.
- If control signal from module is absent, test the module driver output and associated wiring; consult wiring diagrams and service manual for pinouts. Replace or repair module only after confirming wiring and grounds are good.
- After repairs, clear codes and perform a function test; confirm no reoccurrence of B1348.
Likely causes
- Corroded or loose relay socket pins or connector
- Blown fuse protecting the defogger circuit
- Defective relay (open coil or contact)
- Open circuit in the harness between relay and heater grid
Fault status
Status
Heated rear window relay - open circuit detected
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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Code
B1348
FIAT
B — Body
Heated rear window relay open circuit
Views:
UK: 1
EN: 7
RU: 2
AI status
Completed
Completed
100%
Causes
- Blown fuse for the rear window heater or relay coil circuit
- Defective rear window/heater relay (open internal coil or contact)
- Damaged, corroded or disconnected wiring or connectors in relay control or power feed
- Poor or missing ground at relay or rear window heater
- Faulty body control module / relay driver output
- Failed rear window heating grid (open circuit in the grid) or connector fault
Symptoms
- Heated rear window does not turn on
- Rear window heater indicator lamp may not illuminate
- No clicking sound from relay when the heater switch is operated
- Diagnostic trouble code B1348 stored in the body control module
What to check
- Verify accessory/battery voltage at the relay power terminal with ignition on
- Check for fuse continuity for the rear window heater and related circuits
- Listen for relay click when defogger is commanded; if absent, check coil control voltage
- Inspect relay and socket for corrosion, burning, or loose terminals
- Measure continuity between relay output and rear window heater connector
- Scan modules for additional related DTCs and relevant freeze frame data
Signal parameters
- Battery voltage at relay supply terminal: ~12–14 V when ignition/accessory power is on
- Relay coil control: either battery voltage or ground drive depending on chassis design; active state should change coil terminal to near 0 V (ground‑switch) or near battery voltage (positive‑switch)
- Typical relay coil resistance: ~50–200 ohms (coil current ≈ 60–240 mA) — varies by relay
- Closed relay contact voltage drop:
- Rear window heater current draw: typically several amps (commonly 5–20 A depending on vehicle); open circuit will show very low or infinite resistance at the heater connector
Diagnostic algorithm
- Read and record freeze frame data and any other stored DTCs with an OBD scanner.
- Visually inspect relay, relay socket, related fuses, and wiring for obvious damage, corrosion, or loose connections.
- Check fuse(s) for continuity and replace if blown. Retest function.
- With ignition on, measure battery voltage at the relay power terminal. If no power, trace upstream fuse/junction for loss of supply.
- Command the rear window heater on while monitoring the relay coil terminals: verify the control terminal changes state (to ground or to +12 V depending on design). If control signal is present but relay does not click, substitute a known-good relay and retest.
- If relay clicks but heater still inoperative, measure voltage at the relay output terminal while activated. If voltage is present at relay output but not at the rear window connector, perform continuity check of harness between relay and heater.
- Measure resistance of the rear window heating grid (with power removed). Infinite or very high resistance indicates an open grid or broken connector.
- Check ground continuity from the heater ground to chassis; repair any poor grounds.
- If control signal from module is absent, test the module driver output and associated wiring; consult wiring diagrams and service manual for pinouts. Replace or repair module only after confirming wiring and grounds are good.
- After repairs, clear codes and perform a function test; confirm no reoccurrence of B1348.
Likely causes
- Corroded or loose relay socket pins or connector
- Blown fuse protecting the defogger circuit
- Defective relay (open coil or contact)
- Open circuit in the harness between relay and heater grid
Fault status
Status
Heated rear window relay - open circuit detected
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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Code
B1348
HUMMER
B — Body
Very Low A/C Refrigerant Pressure
Views:
UK: 3
EN: 10
RU: 7
AI status
Completed
Completed
100%
Causes
- Blown fuse for the rear window heater or relay coil circuit
- Defective rear window/heater relay (open internal coil or contact)
- Damaged, corroded or disconnected wiring or connectors in relay control or power feed
- Poor or missing ground at relay or rear window heater
- Faulty body control module / relay driver output
- Failed rear window heating grid (open circuit in the grid) or connector fault
Symptoms
- Heated rear window does not turn on
- Rear window heater indicator lamp may not illuminate
- No clicking sound from relay when the heater switch is operated
- Diagnostic trouble code B1348 stored in the body control module
What to check
- Verify accessory/battery voltage at the relay power terminal with ignition on
- Check for fuse continuity for the rear window heater and related circuits
- Listen for relay click when defogger is commanded; if absent, check coil control voltage
- Inspect relay and socket for corrosion, burning, or loose terminals
- Measure continuity between relay output and rear window heater connector
- Scan modules for additional related DTCs and relevant freeze frame data
Signal parameters
- Battery voltage at relay supply terminal: ~12–14 V when ignition/accessory power is on
- Relay coil control: either battery voltage or ground drive depending on chassis design; active state should change coil terminal to near 0 V (ground‑switch) or near battery voltage (positive‑switch)
- Typical relay coil resistance: ~50–200 ohms (coil current ≈ 60–240 mA) — varies by relay
- Closed relay contact voltage drop:
- Rear window heater current draw: typically several amps (commonly 5–20 A depending on vehicle); open circuit will show very low or infinite resistance at the heater connector
Diagnostic algorithm
- Read and record freeze frame data and any other stored DTCs with an OBD scanner.
- Visually inspect relay, relay socket, related fuses, and wiring for obvious damage, corrosion, or loose connections.
- Check fuse(s) for continuity and replace if blown. Retest function.
- With ignition on, measure battery voltage at the relay power terminal. If no power, trace upstream fuse/junction for loss of supply.
- Command the rear window heater on while monitoring the relay coil terminals: verify the control terminal changes state (to ground or to +12 V depending on design). If control signal is present but relay does not click, substitute a known-good relay and retest.
- If relay clicks but heater still inoperative, measure voltage at the relay output terminal while activated. If voltage is present at relay output but not at the rear window connector, perform continuity check of harness between relay and heater.
- Measure resistance of the rear window heating grid (with power removed). Infinite or very high resistance indicates an open grid or broken connector.
- Check ground continuity from the heater ground to chassis; repair any poor grounds.
- If control signal from module is absent, test the module driver output and associated wiring; consult wiring diagrams and service manual for pinouts. Replace or repair module only after confirming wiring and grounds are good.
- After repairs, clear codes and perform a function test; confirm no reoccurrence of B1348.
Likely causes
- Corroded or loose relay socket pins or connector
- Blown fuse protecting the defogger circuit
- Defective relay (open coil or contact)
- Open circuit in the harness between relay and heater grid
Fault status
Status
Heated rear window relay - open circuit detected
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
Similar codes
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Code
B1348
Other
B — Body
Heated Backlite Relay Circuit Open
Views:
UK: 18
EN: 16
RU: 17
AI status
Completed
Completed
100%
Causes
- Blown fuse for the rear window heater or relay coil circuit
- Defective rear window/heater relay (open internal coil or contact)
- Damaged, corroded or disconnected wiring or connectors in relay control or power feed
- Poor or missing ground at relay or rear window heater
- Faulty body control module / relay driver output
- Failed rear window heating grid (open circuit in the grid) or connector fault
Symptoms
- Heated rear window does not turn on
- Rear window heater indicator lamp may not illuminate
- No clicking sound from relay when the heater switch is operated
- Diagnostic trouble code B1348 stored in the body control module
What to check
- Verify accessory/battery voltage at the relay power terminal with ignition on
- Check for fuse continuity for the rear window heater and related circuits
- Listen for relay click when defogger is commanded; if absent, check coil control voltage
- Inspect relay and socket for corrosion, burning, or loose terminals
- Measure continuity between relay output and rear window heater connector
- Scan modules for additional related DTCs and relevant freeze frame data
Signal parameters
- Battery voltage at relay supply terminal: ~12–14 V when ignition/accessory power is on
- Relay coil control: either battery voltage or ground drive depending on chassis design; active state should change coil terminal to near 0 V (ground‑switch) or near battery voltage (positive‑switch)
- Typical relay coil resistance: ~50–200 ohms (coil current ≈ 60–240 mA) — varies by relay
- Closed relay contact voltage drop:
- Rear window heater current draw: typically several amps (commonly 5–20 A depending on vehicle); open circuit will show very low or infinite resistance at the heater connector
Diagnostic algorithm
- Read and record freeze frame data and any other stored DTCs with an OBD scanner.
- Visually inspect relay, relay socket, related fuses, and wiring for obvious damage, corrosion, or loose connections.
- Check fuse(s) for continuity and replace if blown. Retest function.
- With ignition on, measure battery voltage at the relay power terminal. If no power, trace upstream fuse/junction for loss of supply.
- Command the rear window heater on while monitoring the relay coil terminals: verify the control terminal changes state (to ground or to +12 V depending on design). If control signal is present but relay does not click, substitute a known-good relay and retest.
- If relay clicks but heater still inoperative, measure voltage at the relay output terminal while activated. If voltage is present at relay output but not at the rear window connector, perform continuity check of harness between relay and heater.
- Measure resistance of the rear window heating grid (with power removed). Infinite or very high resistance indicates an open grid or broken connector.
- Check ground continuity from the heater ground to chassis; repair any poor grounds.
- If control signal from module is absent, test the module driver output and associated wiring; consult wiring diagrams and service manual for pinouts. Replace or repair module only after confirming wiring and grounds are good.
- After repairs, clear codes and perform a function test; confirm no reoccurrence of B1348.
Likely causes
- Corroded or loose relay socket pins or connector
- Blown fuse protecting the defogger circuit
- Defective relay (open coil or contact)
- Open circuit in the harness between relay and heater grid
Fault status
Status
Heated rear window relay - open circuit detected
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 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
0
👎 Dislike
0
Send to email