Wiring harness chafed or shorted to a live feed between the transmission control unit and the gearbox, often where it passes the gearbox connector; Faulty pressure control solenoid 3 with an internal short; Damaged, corroded or oil-contaminated gearbox internal harness or connector; Fault inside the transmission control unit (mechatronic unit on some gearboxes) driver circuit; Water or fluid ingress into the connector or control unit; Outdated control unit software where a known fault exists for that gearbox.

P1825

Pressure Control Solenoid 3 Short To B+.

Volkswagen
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
8: AreaTransmission
25: FaultThe specific fault in that area

What it means

On Volkswagen, P1825 means the transmission control unit has detected that the circuit for pressure control solenoid 3 in the automatic gearbox is shorted to battery positive (B+). The control unit sees a voltage on the solenoid circuit that should not be there, or cannot drive the solenoid as commanded. The gearbox will usually go into a fallback (limp) mode to protect itself.

Symptoms

Gearbox warning light or malfunction indicator lamp on
Gearbox stuck in one gear or limp mode
Harsh, delayed or flared gear changes
Loss of certain gears or no manual shift control
Reduced performance and poor economy

Possible causes

Wiring harness chafed or shorted to a live feed between the transmission control unit and the gearbox, often where it passes the gearbox connectorlikely
Faulty pressure control solenoid 3 with an internal shortlikely
Damaged, corroded or oil-contaminated gearbox internal harness or connectorlikely
Fault inside the transmission control unit (mechatronic unit on some gearboxes) driver circuitpossible
Water or fluid ingress into the connector or control unitpossible
Outdated control unit software where a known fault exists for that gearboxrare

How to diagnose

Read all stored codes and freeze frame data, noting whether the fault is current or intermittent and whether other solenoid or supply voltage codes are present
Check the gearbox fluid level and condition as the procedure for the specific gearbox requires, as some have a set check procedure and temperature
Visually inspect the wiring and connectors between the gearbox and control unit for chafing, pin damage, corrosion and fluid contamination
Check battery condition and charging voltage, as low or unstable voltage can cause misleading faults
With the connector disconnected, test the solenoid 3 circuit for a short to positive and measure solenoid resistance against the manufacturer's specification
Check the live feed and earth to the control unit and gearbox unit
Check for applicable software updates or technical bulletins for the specific model and gearbox type
Clear the code and road test to see whether it returns, monitoring live data for solenoid operation

How to fix

Repair or replace the damaged wiring section or connector, using proper sealed repairs
Replace the faulty pressure control solenoid, or the mechatronic or valve body unit if the solenoid is not available separately on that gearbox
Replace the internal gearbox harness or connector if it is damaged or contaminated
Replace or repair the transmission control unit if the driver circuit is confirmed faulty, then adapt it as required
Update the control unit software if a relevant update is available for that gearbox
Correct the fluid level or change the fluid if it is found to be contaminated or incorrect

Can I keep driving?

Medium severity

The car can usually be driven carefully in limp mode for a short distance to a workshop, but it should be fixed soon. Continued driving with harsh or incorrect pressure control may damage the gearbox.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.