Damaged, corroded or loose connector or wiring to the ADR control module, including its power and earth supplies; Fault on the powertrain CAN bus wiring, such as an open circuit, short or chafed twisted pair; Low battery voltage or poor battery terminal or earth connections causing modules to drop out; Failed ADR control module that has stopped transmitting; Water ingress into the module or connector, for example from a leaking seal or a wet footwell; Software or coding mismatch after a module replacement or update; Fault in the gateway or another bus participant disrupting communication.

P1864

Data Bus Powertrain Missing Message From ADR Control Module.

Volkswagen
Powertrain
Manufacturer code
Medium severity

How this code is built

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

What it means

P1864 on a Volkswagen means the engine control unit stopped receiving an expected message from the control module labelled 'ADR' on the powertrain CAN data bus. The engine control unit logs the fault when messages from that module are missing or time out. Which unit 'ADR' refers to depends on the model and equipment level, so confirm it from the model-specific wiring diagram and module list.

Symptoms

Engine management warning light on
Other warning lights or messages in the dash cluster, depending on the module involved
Loss of the function controlled by the ADR module
Reduced performance or limp-home behaviour on some vehicles
Several modules reporting communication faults at the same time
Intermittent fault that appears after starting or when driving over bumps

Possible causes

Damaged, corroded or loose connector or wiring to the ADR control module, including its power and earth supplieslikely
Fault on the powertrain CAN bus wiring, such as an open circuit, short or chafed twisted pairlikely
Low battery voltage or poor battery terminal or earth connections causing modules to drop outpossible
Failed ADR control module that has stopped transmittingpossible
Water ingress into the module or connector, for example from a leaking seal or a wet footwellpossible
Software or coding mismatch after a module replacement or updaterare
Fault in the gateway or another bus participant disrupting communicationrare

How to diagnose

Read all stored codes from every control module and note the freeze frame data, checking whether the fault is current or stored
Check for other communication or bus codes in other modules, which point to a bus-wide problem rather than one module
Check battery condition and charging voltage, then inspect battery terminals and main earth points
Identify the ADR module for this model and engine from the wiring diagram, then inspect its connectors for damage, corrosion, moisture or pushed-back pins
Check the module's fuses, power supplies and earths with a multimeter
Wiggle-test the harness while monitoring live data to find intermittent faults
Measure the CAN high and CAN low wiring for continuity, shorts and correct terminating resistance as per the wiring diagram
Check for the correct part number, coding and software version for the module and compare with the manufacturer's data

How to fix

Repair or replace damaged wiring, connectors or terminals found on the module or CAN bus harness
Restore good power and earth connections, and charge or replace a weak battery
Dry out and repair any water ingress, fix the leak source, and replace corroded connectors
Replace the ADR control module if it is confirmed faulty, then code and adapt it to the vehicle as required
Update or correct the module software and coding if a mismatch or known software fault is confirmed

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but book it in soon because the lost function or reduced performance may get worse. If other warning lights come on, or the car goes into limp mode or handles unusually, stop driving and have it checked.

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