B1747
Mirror Passenger Horizontal Switch Circuit Short To Battery
Body Chassis/Safety Mirror Control Circuit 🟢 Low — Fix at next service
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What This Actually Means
In plain language — no jargon

The passenger side mirror's horizontal adjustment switch is sending a constant 'full power' signal to the ECU, like a stuck accelerator pedal. This prevents normal mirror control because the circuit thinks the switch is permanently pressed.

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Symptoms You May Notice
3 known symptoms for this code
Passenger mirror won't move horizontally or moves erratically
Mirror control switch unresponsive or stuck in one direction
Dashboard warning light or mirror fault indicator illuminated
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors voltage levels on the mirror switch circuit, expecting variable voltage as the driver adjusts the switch position. When the circuit shorts to battery voltage (12V), the ECU detects an abnormal constant high signal instead of the normal range of 0-5V variations. This persistent high voltage indicates a wiring short or switch failure.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Mirror Switch Voltage 0-5V (variable based on switch position) >10V continuous (battery voltage)
Circuit Resistance Variable 1k-100k ohms <100 ohms (short to battery)
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Wiring harness connector
Disconnect and inspect the mirror control connector for corrosion, moisture, or damaged pins causing the short.
2
Mirror switch assembly
Replace the faulty switch if corrosion or internal damage is confirmed and connector checks pass.
3
Wiring and relay
Repair or replace damaged wiring between the switch and ECU, or the mirror control relay if shorted.