What Does B1402 Mean?
This code indicates the Body Control Module (BCM) has detected an electrical fault in the driver's side power window down switch circuit. The BCM monitors the switch input signal and has identified either an open circuit, short to ground, short to power, or abnormal resistance in the switch or its wiring. This prevents the BCM from receiving proper input signals when the driver attempts to lower the window using the down position of the switch.
Common Causes
45%
Faulty driver door master power window switch assembly with internal contact wear or corrosion
30%
Damaged or corroded wiring between BCM and driver window switch, often in door jamb flex area
15%
Corroded or loose electrical connector at driver window switch or BCM
10%
Failed Body Control Module with internal circuit damage
Diagnostic Steps
1
Step 1: Perform visual inspection of driver door master window switch for physical damage, burnt contacts, or moisture intrusion. Remove switch assembly and inspect connector terminals for corrosion, pushed-back pins, or damage
2
Step 2: Using a digital multimeter, check for proper voltage supply at window switch connector (typically 12V on power feed) and verify ground circuit has less than 0.1 ohms resistance to chassis ground
3
Step 3: With switch disconnected, use multimeter in resistance mode to test switch continuity through down position. Should show continuity when pressed down, open circuit when released. Compare readings to manufacturer specifications
4
Step 4: Inspect door jamb wiring harness for broken wires, chafing, or pinched conductors. Flex harness while monitoring circuit continuity to identify intermittent faults
5
Step 5: Back-probe the BCM connector at the window down switch input circuit and verify proper signal voltage changes when manually operating the switch (if accessible). Should see voltage change between 0V and 12V or appropriate signal range
6
Step 6: If all wiring and switch test good, substitute known-good master window switch assembly to confirm diagnosis. Clear codes and cycle window switch through all positions to verify repair
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an electrical fault in the driver's side power window down switch circuit. The BCM monitors the switch input signal and has identified either an open circuit, short to ground, short to power, or abnormal resistance in the switch or its w...
The most common cause of B1402 (Driver Power Window Down Switch Circuit Failure) is: Faulty driver door master power window switch assembly with internal contact wear or corrosion
Typical repair costs for B1402 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as this does not affect vehicle operation or safety systems. Window may still function in up position or via other switch positions, though complete window control may be lost until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1402 to identify the root cause.
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Quick Info
Category
Body
System
Body Electrical System
Difficulty
Type
Manufacturer
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