B1737
Mirror Driver Horizontal Switch Circuit Failure
Body Chassis/Safety Mirror Control 🟢 Low — Fix at next service
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What This Actually Means
In plain language — no jargon

The side mirror's horizontal adjustment motor or its control switch isn't communicating properly with the vehicle's control module. It's like a broken remote control—the command is sent, but the mirror doesn't respond.

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Symptoms You May Notice
3 known symptoms for this code
Driver side mirror won't move left/right or moves erratically
Mirror adjustment buttons unresponsive or stuck
Warning light or message displayed on dashboard
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors the voltage signal from the mirror switch circuit when the horizontal adjustment button is pressed. It expects a valid signal within a specific voltage range; if the signal is absent, shorted, or out of range for too long, a fault is logged.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Switch Signal Voltage 0.5V to 4.5V (varies by position) Open circuit (5V+) or short to ground (0V sustained)
Motor Current Draw 1-5 amps during movement No current or excessive current (>8A)
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Mirror switch connector
Disconnect and reconnect the mirror switch harness to clean contacts and reseat the connector.
2
Mirror switch assembly
Replace the faulty horizontal adjustment switch if contacts are corroded or stuck.
3
Mirror motor and gearbox
Replace the entire mirror motor assembly if the switch tests good but motor still won't respond.