Code
B1402
Other
B — Body
Driver Power Window Down Switch Circuit Failure
AI status
Completed
Completed
100%
Causes
- Faulty driver power window DOWN switch
- Open, short to ground, or short to battery in the switch harness
- Poor or corroded connector pins at switch or body control module (BCM)
- Blown fuse or lost ignition/switched power feed to switch circuit
- Water intrusion or contamination in switch assembly
- Faulty body control module / window control module input
Symptoms
- Driver window will not move down (or does not respond to DOWN command)
- Window may work intermittently or only from passenger switches
- No sound of window motor when holding DOWN switch
- Other power window functions may work normally
- Fault indicator or stored DTC present in vehicle data
What to check
- Retrieve freeze-frame and live data with a scan tool; confirm B1402 and any related codes
- Visually inspect driver door switch assembly and harness for damage or water
- Check related fuses and ignition/switched power feed to the switch
- Backprobe switch connector and measure voltages while operating DOWN switch
- Measure continuity and resistance between switch and BCM connector pins
- Wiggle test harness with probe attached to reproduce intermittent behavior
Signal parameters
- Reference/supply voltage: typically 5 V logic reference or 12 V switched (design dependent)
- Expected switch output: either pulled to ground or to reference voltage when DOWN is pressed
- Open/inactive: open circuit or high impedance (infinite ohms)
- Actuated: near 0 Ω to ground or near reference voltage (verify with vehicle-specific wiring)
- Intermittent faults: unstable voltage or bouncing between expected states
Diagnostic algorithm
- Verify symptoms and confirm code with scan tool. Record any other related codes (BCM, LIN/CAN).
- Visually inspect driver door switch, connector, and door harness (look at wiring near hinge/door jamb).
- Check fuses and verify switch supply voltage with ignition ON. Repair power feed if missing.
- Backprobe switch connector. With key ON, measure reference/supply voltage and ground. Operate DOWN switch and observe voltage change.
- If no change at switch, test continuity from switch connector to BCM input pin. Repair any open/short.
- If switch signals correctly but window does not move, test window motor and related relays/outputs (separate circuit).
- If wiring and motor are good, remove switch and bench-test or replace with a known-good switch. Re-test.
- If replaced switch still shows fault and wiring checks good, inspect BCM connector and grounds. Consider module input failure and consult manufacturer procedures before replacing BCM.
- After repair, clear codes and perform functional test; verify no recurrence and that live data shows correct switch states.
Likely causes
- Switch internal contact failure or contamination
- Broken wire or chafed insulation in door harness near hinge
- Corroded switch connector terminals
- Connector not fully seated or bent pins
- Intermittent BCM input due to poor ground or internal module fault
Fault status
Status
Driver power window DOWN switch circuit open/short/intermittent — input not within expected range.
Repair difficulty: Medium
Diagnostic time: 0.5 - 1.5 hours
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