Code
B1439
ALFA ROMEO
B — Body
Wiper mode selection switch open circuit
Views:
UK: 6
EN: 6
RU: 6
AI status
Completed
Completed
100%
Causes
- Broken or disconnected wiring between wiper mode switch and BCM
- Corroded, bent or loose connector pins at switch or BCM
- Failed wiper mode selector switch (mechanical/electrical failure)
- Open fuse or poor power/ground for switch or BCM
- Intermittent or lost communication on vehicle network (CAN LIN)
- Faulty BCM or input circuit failure
Symptoms
- Wipers do not change speed or mode when switch is operated
- Intermittent or complete loss of wiper functions (wash, intermittent, low, high)
- Instrument cluster or message indicating service required for wipers
- Related switch controls (e.g., wash) unresponsive while motor may still run in some modes
- DTC B1439 stored and possibly other body network communication DTCs
What to check
- Scan vehicle for B1439 and any related DTCs; note freeze-frame and event counts
- Visually inspect the wiper mode switch, stalk, connectors and wiring for damage or corrosion
- Check fuses and power/ground feeding the switch and BCM
- Operate the switch while monitoring live data or communication messages for the wiper selector input
- Perform continuity and resistance checks from the switch pins to the BCM connector pins with ignition OFF
- Backprobe the switch connector with ignition ON to measure expected voltages or switching voltages
Signal parameters
- Switch output: normally toggles between 0 V (ground) and battery voltage (~12 V) or between defined resistance steps — OEM values required
- Expected continuity: closed circuits in selected positions, open in others — consult wiring diagram for pin-to-pin mapping
- Live data: wiper mode selection parameter should change when stalk is moved
- CAN/LIN: wiper switch message should be present on bus; loss of message indicates wiring/network or module fault
- Resistance: some multi-position switches present characteristic resistances per position — compare to factory specs
Diagnostic algorithm
- Read and record all stored DTCs and freeze-frame data. Clear codes and re-test to confirm reproducibility.
- Inspect fuses and the power/ground at the switch and control module. Repair any blown fuses or poor grounds.
- Visually inspect switch, connectors and harness (steering column area) for damage, corrosion or loose terminals. Repair as necessary.
- With ignition ON, backprobe the switch connector and operate the stalk. Measure voltage on signal pins — verify toggling between expected states (0 V/12 V or specified levels).
- With ignition OFF, disconnect battery if required by service manual, then check continuity and resistance between switch terminals and BCM input terminals to identify open circuits or high resistance.
- If wiring and connectors are good, bench-test or substitute a known-good switch (if available) to verify switch operation.
- If switch and wiring verify OK but input not seen at BCM, check for CAN/LIN messages and communication errors. Use scope or CAN tool to confirm.
- If communication is present but BCM input is dead, consider BCM input driver fault and consult manufacturer procedures for BCM testing or replacement.
- After repairs, clear codes and verify correct operation of all wiper modes through full function test and road test.
Likely causes
- Worn or contaminated switch contacts inside the stalk/switch
- Damaged wiring harness (chafed, pinched, or broken wires)
- Connector corrosion or pushed-out terminal at steering column or BCM
- Blown fuse supplying switch or control module
- Fault in BCM input driver if wiring and switch test good
Fault status
Status
Wiper mode selection switch open circuit detected. Check switch, wiring, connectors, fuses and module communication before replacement.
Repair difficulty: Medium
Diagnostic time: 0.5 - 1.5 hours
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