P1847

What it means

On Volkswagen group vehicles, P1847 means the engine or transmission control unit has received a fault message from, or lost proper communication with, the brake system control unit (ABS/ESP), and is telling you to check that unit's own fault memory. The code is a pointer rather than a fault in the engine or gearbox itself. The real fault is stored in the brake control unit, and the exact signal or trigger can vary by model and year.

Symptoms

• ABS and/or ESP warning light on the dashboard
• Engine or gearbox warning light, or a stored fault with no obvious driveability problem
• Traction control or stability control not working or switched off
• Reduced engine torque or limp-style behaviour on some models
• Cruise control or hill hold unavailable
• Possible harsh or altered gearbox shifting on automatics if wheel speed data is missing

Possible causes

• Stored fault in the brake control unit, such as a wheel speed sensor signal fault or implausible signallikely
• Damaged wheel speed sensor wiring, connector or sensor, or a damaged or dirty tone ring/encoderlikely
• Low or poor battery voltage or a weak earth causing temporary brake unit faults and communication dropoutspossible
• CAN bus wiring fault or connector corrosion between the brake unit and other control unitspossible
• Brake pressure sensor, steering angle sensor or brake light switch fault feeding the brake unitpossible
• Fault inside the brake control unit or hydraulic unitrare
• Outdated software in the brake or engine control unit, where a known issue exists for that modelrare

How to diagnose

1. Read all fault codes from every control unit, especially the brake system (ABS/ESP) unit, and record them with freeze frame data
2. Note whether the fault is current or intermittent and whether the warning lights are on now
3. Check battery condition and charging voltage, and inspect battery terminals and earth connections
4. Visually inspect wheel speed sensors, their wiring and connectors at each wheel for damage, corrosion or contamination
5. Inspect tone rings or encoder surfaces for damage, rust build-up or debris
6. Check live wheel speed data on a road test and compare all four wheels for dropouts or mismatches
7. Check the steering angle sensor, brake light switch and brake pressure sensor readings for plausibility
8. Test CAN bus wiring and connectors for continuity and resistance if communication faults are stored

How to fix

• Diagnose and repair the fault actually stored in the brake control unit, as P1847 only points to it
• Replace a faulty wheel speed sensor, or repair damaged wiring or connectors
• Clean or replace a damaged tone ring or wheel bearing with integrated encoder as the model requires
• Restore good battery condition and repair poor earth or power supply connections
• Repair CAN bus wiring or connector faults
• Replace or repair the brake control unit only after other causes are ruled out, and update software if the manufacturer lists a fix for the model

Can I keep driving?

This code for other makes

• P1847Buick2-3 Shift Solenoid Circuit High Voltage
• P1847Cadillac2-3 Shift Solenoid Circuit High Voltage
• P1847Chevrolet2-3 Shift Solenoid Circuit High Voltage
• P1847GM2 3 Shift Solenoid Circuit High Voltage
• P1847GMC2 3 Shift Solenoid Circuit High Voltage
• P1847Oldsmobile2-3 Shift Solenoid Circuit High Voltage
• P1847OtherTransmission Transfer Case Contact Plate 'A' Open Circuit
• P1847Saturn2-3 Shift Solenoid Circuit High Voltage

Nearby codes

• P1844VolkswagenCheck DTC Memory Of Central Electronic Control ECU
• P1848VolkswagenCheck DTC Memory Of Engine ECU