B1439 Wiper Mode Switch Circuit Open
The B1439 code indicates an open circuit in the windshield wiper mode selector switch, typically found in Toyota and Lexus vehicles. This code is triggered when the Body Control Module (BCM) or wiper control module detects a break in the electrical circuit that allows the driver to select wiper modes (intermittent, low, high). The expected voltage signal does not reach the control module due to a wiring break or component failure.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty or worn wiper mode selector switch
- Open or cut wiring between the switch and control module
- Corroded, oxidized, or damaged connector pins at the switch
- Internal failure in the Body Control Module (BCM) input circuit
- Blown wiper circuit fuse
- Poor ground connection in the switch circuit
3. Symptoms You Will Notice
- Wiper modes not working or intermittent operation
- Wipers stuck in one mode (e.g., only high speed)
- No wiper operation at all
4. Step-by-Step Diagnosis
Check the wiper circuit fuse and replace if blown.
Inspect the wiper mode switch connector for corrosion, damage, or loose pins.
Test continuity of the wiring between the switch and BCM using a multimeter.
Verify the switch itself by measuring resistance across its terminals in each mode.
If all else passes, test the BCM input circuit or consider BCM replacement.
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive, but wiper functionality may be limited or absent, which can be hazardous in rain or snow. Repair is recommended soon.
How much does it cost to fix?▼
Typical repair costs range from $100 to $300, depending on whether the switch, wiring, or BCM needs replacement. Diagnostic fees may add $50–$100.