Bosch and other throttle bodies

[DonWillson]

Hi gang,

Since the very first discovery of the Volvo MM ETM problem there have been questions about using a Bosch unit or replacing the throttle position potentiometer strips. Let me summarize.

As far as I can tell Volvo is the only car that has a 'smart' ETM. Others have a throttle body with a potentiometer sensor but it is just a dumb sensor. The MM ETM recieves a signal fromt he accelerator pedal and the internal computer on the ETM drives the throttle to the appropriate position. Other cars, that use a Bosch, have external circuits that drive the throttle plate. Even my Ford Freestyle has a potentiometer TPS but it is held on by 4 screws and can be replaced in 10 minutes for a cost of about $140.

As far as repairing the ETM yourself; it could be done, and has been done in the UK with little success. To do it you would have to break solder joints, remove potting compound, replace the resistance film, replace the wiper without bending the feelers, etc and etc. Resolder the connections and reseal the soldered area with moisture proof material.

[Gimpster]

You just answered a couple of the questions from the other thread. I had a feeling the MM ETM was too "smart" for its own good.

The other DBW systems I've looked at/worked with had external modules like your Ford. The TB itself was pretty dumb, just the usual rotary pot and a motor.

That all being said, the electronics package seems pretty robust as you noted on your site. The pot design was just miserable