Severity Medium
B1540

Driver Mirror Switch Circuit Open

📅 Last reviewed: July 2026
What does the B1540 code mean?

The Driver Door Module (DDM) has detected an open circuit in the driver's side mirror switch assembly. This prevents the adjustment signals (up/down, left/right) from reaching the control module, disabling the power mirror adjustment function.

Medium
Severity
Variable
Typical Cost
Medium
Frequency

1. Commonly Affected Makes

FordLincolnMercury

2. Most Common Causes

3. Symptoms You Will Notice

4. Step-by-Step Diagnosis

1

Check for power and ground at the mirror switch connector using a multimeter

2

Inspect the switch and door harness connectors for corrosion, damage, or loose pins

3

Test continuity of the signal wires between the switch and DDM

4

If wiring and switch are good, test the DDM by swapping with a known good module or using a scan tool

5. Frequently Asked Questions

Is it safe to drive?

Yes, it is safe to drive. The fault only affects the power mirror adjustment; the mirror itself remains in its last position and does not impact vehicle safety.

How much does it cost to fix?

Repair costs typically range from $100 to $400, depending on whether the switch, wiring, or DDM needs replacement and the labor rates in your area.

6. Related Codes

Need an OBD2 Scanner for the B1540? Compare the best scanners compatible with all vehicles
🛒 View OBD2 Scanners →