How is fault code B1858 fixed?

Measure the supply at the sensor, then decide which side is loading it. - Measure the sensor supply voltage at the motor connector with the ignition on - Unplug the sensor and remeasure, a recovery points to a shorted sensor - With the module unplugged, ohm the supply wire to ground to find an external short - Do a voltage drop test on the supply wire to expose high resistance - Inspect the door interior, vapour barrier and drain holes for moisture - Clean or renew corroded terminals and repair the boot wiring - Replace the window motor with its integrated sensor, then perform the window relearn

Climate Control A/C Pressure Switch Circuit Failure

Jump to the fix

Severity

Medium

Can I keep driving?

Usually drivable, but get it diagnosed without delay.

First step

Measure the supply at the sensor, then decide which side is loading it.

BBody
1Manufacturer-specific
8Body
58Sequence number

What does it mean?

B1858 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Driver Window Position Sensor Power Supply Low .

Symptoms

Auto up and auto down stop working and the window only moves while the switch is held
Anti-pinch protection disabled, or the window bounces back near the top
Window position has to be relearned repeatedly
Position or pulse count values missing on the scan tool
Driver window responds more slowly than the other windows

Likely causes

Sensor supply wire shorted to ground
Position sensor inside the window motor shorted and loading its own supply
Corroded connector at the window motor after water intrusion in the door
Chafed conductors inside the door hinge boot
High resistance in the supply wire from a poor terminal or a corroded splice
Module voltage regulator for the sensor supply failing under load
Aftermarket accessory tapped into the sensor supply circuit

How to fix it

Measure the sensor supply voltage at the motor connector with the ignition on
Unplug the sensor and remeasure, a recovery points to a shorted sensor
With the module unplugged, ohm the supply wire to ground to find an external short
Do a voltage drop test on the supply wire to expose high resistance
Inspect the door interior, vapour barrier and drain holes for moisture
Clean or renew corroded terminals and repair the boot wiring
Replace the window motor with its integrated sensor, then perform the window relearn

Codes From the Same System

All Fault Codes

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This information follows the generic OBD-II definition and does not replace a vehicle-specific diagnosis. The severity rating is rule-based; an authorised diagnostic reading is required for a definitive answer.