2006 E320 Cdi 7G- What is the Auxiliary battery's function?

[jon_viola]

As it says. Wondering what systems rely on the auxiliary battery.

Thanks

Jon

 

[whitenemesis]

The auxiliary battery supplies electrical energy for a limited time if the systems battery voltage is low.

Have read of this MB training doc

 

[jon_viola]

Thanks, does it have anything to do with the gearbox control?

 

[Merc Owner 2B]

The auxiliary battery supplies electrical energy for a limited time if the systems battery voltage is low.

Have read of this MB training doc

I guess these training docs are hard to come by whitenemesis?

 

[whitenemesis]

Thanks, does it have anything to do with the gearbox control?

Not directly but as part of the vehicle's electrical supply low or unstable voltages can affect the TCU. Probably less common with dual battery vehicles as one has the extra support afforded by this set-up.

 

[whitenemesis]

I guess these training docs are hard to come by whitenemesis?

MBUSA allow quite free access to a lot of info

MBUSA Technical Training PDF files

 

[GordonTarling]

Jon - if your car is a 7G, then it's probably a facelift model and thus won't have the auxiliary battery. It's mainly there to ensure the SBC is powered reliably.

 

[jon_viola]

Thanks for your help guys. It is the middle model with the 7g and V6 but the non facelift. When I did a scan of the fault codes it came up with an error saying battery fully discharged. So I guess it's got one as the car starts fine and there are no warnings on the dash.

My reason for asking is that my gearbox has stopped working at the same time. It will select but has little forward drive although oddly reverse is fine.

Today I will change the aux battery/tranny fluid and filter and also an O2 sensor which between them hopefully will sort it out!

Thanks again

Jon