Nanocom Fault Codes and Faults

**steve_a** · 5th April 2018, 05:09 PM

I've never been able to made head nor tail of the shift speed values, I've seen all empty bar one, a few more filled in and mixes of stuff. Unless someone has a guide on them then I've consigned them to the non-informative, non-interesting area of nanocom.

**sierrafery** · 5th April 2018, 08:13 PM

For that P0721 see the MAF reading at your full boost and if it's well above 600 you better wind up the boost a bit IMO cos at so high MAF reading(if it's accurate) the rpm should be high too and you should get at least 1.3 bar, better 1.35 with well set wastegate... unless you have a slight boos leak... the EAT ECU considers that the engine speed is high enough at that point and prevents downshift to not create an engine overspeed so it sends it to limp mode... let's hope you dont have a slipping clutch in the box or something... if this happens with fresh oil and filter too maybe you should run a stall test on the box... i helped a friend with this fault code once and the problem was that the aftermarket crank sensor he fitted gave higher than normal reading, took ages to figure this out but IMO that's not something common

from ZF4HP22EH troubleshooting manual

here are the ambient conditions too as to help in the troubleshooting

**John_D4** · 6th April 2018, 12:18 AM

Thanks Sierrafery. I had to read your post 2 or 3 times for it to make sense. I get it now. That would certainly explain the limp home mode.

Sounds like 1st check is to run it up the expressway Hill at full boost and make note of boost pressure and MAF reading (probably coolant also while I’m there). I might do that and report back before I fiddle with the turbo. I have never done that before so I’d rather make sure I’m understanding things before I adjust.

I’m kinda hoping that that will ‘fix’ the issue. Although it is a LR...nothing is ever that simple!

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