M-Box into my H-Box without RECODE = What happens?

**klhbeetle** · 08-19-2009 02:09 PM

I've got an M-box ECU I want to swap in for my H-Box. Can I run this in my car without cluster recode? What happens? I plan to cluster recode soon, but I'm waiting on hardware and I want to test out the ECU without recoding. I searched and it seems the car will run, just wondering about negative side effects.

Is this unwise?

**mholme** · 08-19-2009 02:13 PM

You'll get a CEL and some powertrain codes.

**RedRocketS4** · 08-19-2009 03:11 PM

i changed my h-box out for a chipped m-box without recoding. I had a code, but no CEL. you should be good.

**NOTORIOUS VR** · 08-19-2009 03:20 PM

H + M boxes should work without the need to recode anything... since both cars had ESP and Hitachi MAFs... BUT... if you swapped the H box into your car and it was a Hitachi conversion and your car does NOT have ESP then you will need to recode the "new" M-box to no ESP.

That's about it.

**mholme** · 08-19-2009 03:29 PM

The clusters expect different values, H to M. H should see "0" where M wants "1025", so there's where the data bus code comes from. I may have been mistaken about it throwing a CEL.

**klhbeetle** · 08-19-2009 05:07 PM

I've heard you need to recode your cluster going h-box to m-box. But no CELs? I'll give it a try, just don't want to do damage. I have ESP, don't know if the previous car had ESP, does it matter going the other way?

**mholme** · 08-19-2009 05:39 PM

Originally Posted by klhbeetle

I've heard you need to recode your cluster going h-box to m-box. But no CELs? I'll give it a try, just don't want to do damage. I have ESP, don't know if the previous car had ESP, does it matter going the other way?

Need to, no you don't really need to, but you WILL have powertrain data bus codes, probably not a CEL. I think a lot of people realize they have this code when the CEL pops up for another reason and they scan the car. If you're putting in a true M box ECU, it's from an ESP eqipped car and no further coding needs to be done outside of the channel 60 "1025" coding.

**klhbeetle** · 08-30-2009 10:02 AM

Update:
Nothing happens. Not yet anyways. I swapped in the M-Box MTM stg II ECU along with the 5 bar FPR and everything runs great. No CELs, I don't know if there are any codes, but I'll check once I get a PC to VAG it.

**NOTORIOUS VR** · 08-30-2009 10:53 AM

^^^ The only code you'll have is the Power Supply code...

Like I said, H, M and T boxes are all from ESP & Hitachi equipped cars, so unless they were recoded by someone else to be used in a non ESP car, they will work no problem and you will get no codes.

I've been though this many a times.