VCDS: Adjusting Glow Plug Timer on VAG TDIs (Articles)

When is it actually sensible to change the preheating time of the glow plugs?

Normally not, because in 'standard operation', starting problems or white smoke in TDIs usually have their cause in engine errors that must be addressed first. Examples include a misadjusted static injection timing, faulty glow plugs, or a defective coolant temperature sensor.

However, there are cases where extending the preheating time makes sense: when operating a TDI engine with vegetable oil (rapeseed oil) or, possibly, also with biodiesel. Depending on the engine and fuel, the standard preheating may not be sufficient to achieve an acceptable cold start. The following instructions are intended for these cases.

To change the preheating time, the following steps are necessary:

• The engine coolant temperature must be low enough for the glow plugs to activate, e.g., 5°C. Otherwise, no changes will be observed.
Turn on the vehicle's ignition.
Connect to the engine control unit (01) using VCDS.
Perform a login with the code 12233.
Go to adaptation group 12 via "control unit adaptation".
Change the default value (32768), e.g., to 32700, and save the new value.
Disconnect from the engine control unit.
Turn off the ignition and wait a few seconds.
Go back into the engine control unit and perform the same steps as above. Of course, a new value does not need to be saved every time. In field 2 of group 12, you will now see the preheating time that was active after the last "ignition on".