2010 35i sudden loss of power, code 5A53

[enzed4]

I'm starting this thread to document a problem I had today and hopefully any fix that might be applied.
A bit of info:
2010 35i, 84500km, MHD tune stage 1+, 5" FMIC, BMS POD filters (I know, I know - they were on the car when I bought it ).
Cool day today - 14C so no issues with temps (oil temp was around 110C).
I was following another vehicle at around 90km/h, I put the transmission shift lever into the manual mode (I usually just have the button selector set for Sport, but today it was in 'Normal') pulled out and put the foot down about 90%, not flat to the floor.
Almost immediately power seemed to cut dramatically, it felt worse than no turbo boost, but that could just be my imagination, so at this stage I'll just assume no boost. I 'think' I heard a warning 'bong', looked down at the dash and saw what I think was a 'sprocket' symbol (a quick look online tonight and the closest match I can find indicated a transmission fault). I pulled back into traffic and carried on until I could pull over. I then tried several runs from stopped, or rolling slowly, to full boost and had no problems at all - I couldn't reproduce the fault.
When I got home I did a DME scan with the MHD software (I have Carly as well but haven't checked it yet - I don't think it would show anything different) and it showed NO current fault, and nothing in the history that I didn't already know about or have fixed.
So - any ideas what this might have been? Troubleshooting steps? I could flash it back to stock, but if it's a trans problem this won't help. I would like to identify the cause before throwing any fixes at it.
Apologies for the long-winded post, but usually people give little info to go on so maybe this will be more helpful.
Thanks.

[Chippie]

This may not be of any help but could it have been the traction control killing the power, as there was no fault code stored then perhaps there isn’t a fault?

[Smartbear]

Could the clutches have started to slip & the car cut power to protect them?
Rob

[enzed4]

This may not be of any help but could it have been the traction control killing the power, as there was no fault code stored then perhaps there isn’t a fault?

I have seen the DSC/Traction control symbol flashing before and it definitely wasn't that. I was also in too high a gear to lose traction just by putting the foot down - the road was dry and had good grip. I also believe the traction control just tells you there's loss of traction, while trying to apply very minimal braking to get grip back to the driving wheels - it doesn't cut power as far as I'm aware. Thanks for the suggestion.

[enzed4]

Could the clutches have started to slip & the car cut power to protect them?
Rob

This is what I'm worried about. If the DCT is starting to fail, what are my options? Would a flush/service fix this or could it be more serious (expensive), ie failing components?

[Smartbear]

Could the clutches have started to slip & the car cut power to protect them?
Rob

This is what I'm worried about. If the DCT is starting to fail, what are my options? Would a flush/service fix this or could it be more serious (expensive), ie failing components?

They might only be slipping because of the additional power going through them, i think there’s a software patch that increases the clamping force on the clutch packs?
Rob

[enzed4]

Could the clutches have started to slip & the car cut power to protect them?
Rob

This is what I'm worried about. If the DCT is starting to fail, what are my options? Would a flush/service fix this or could it be more serious (expensive), ie failing components?

They might only be slipping because of the additional power going through them, i think there’s a software patch that increases the clamping force on the clutch packs?
Rob

I wonder where one would get that patch?

[enuff_zed]

Worth trying to repeat it, with the lever pushed over, then again but leave the lever lone and select Sport.
May help to isolate the issue a little. Possibly an electrical gremlin instigated by moving the lever?

[Smartbear]

This is what I'm worried about. If the DCT is starting to fail, what are my options? Would a flush/service fix this or could it be more serious (expensive), ie failing components?

They might only be slipping because of the additional power going through them, i think there’s a software patch that increases the clamping force on the clutch packs?
Rob

I wonder where one would get that patch?

I think some remaps incorporate higher clamping force on the clutch packs, an n54 expert will be along soon (R.E92)
Rob

[mcbutler]

This may not be of any help but could it have been the traction control killing the power, as there was no fault code stored then perhaps there isn’t a fault?

If traction control is activated you get an error code and the dash light will flash as its engaging. Like many codes generated though it is not an ERROR code in itself

[mcbutler]

Could the clutches have started to slip & the car cut power to protect them?
Rob

This is what I'm worried about. If the DCT is starting to fail, what are my options? Would a flush/service fix this or could it be more serious (expensive), ie failing components?

New clutch pack if they are slipping, a slipping wet clutch burns the oil as well - if this is the case i hope you have a good warranty.............

[Zforbes]

Are you sure it's gearbox related?

The reason I ask is a friend had a similar problem, loss of power when a accelerating hard shortly after a remap. It turned out that the fuel injectors couldn't provide the amount of fuel the remap was asking for. His choice was either to upgrade the injectors or downgrade the map. It took a while to find it as it didn't happen every time, took it back to the remap garage and never had a problem since.

Wasn't a z4 but one to bare in mind.

[R.E92]

Sprocket symbol is a transmission fault.

Sounds like an over temperature fault but you would need to scan the gearbox for codes. You can do that with something like INPA or ISTA on a laptop or using the Pro Tool app.

An over temperature fault is often triggered by clutch slip which in turn is usually a result of low transmission fluid. I'd check the trans for any leaks.

Clutch slip from too much torque is also a cause but you're nowhere near the limits with MHD stage 1. The DCT can hold about 600nm in standard form and over 700nm with an xHP transmission tune.

[enzed4]

Sprocket symbol is a transmission fault.

Sounds like an over temperature fault but you would need to scan the gearbox for codes. You can do that with something like INPA or ISTA on a laptop or using the Pro Tool app.

An over temperature fault is often triggered by clutch slip which in turn is usually a result of low transmission fluid. I'd check the trans for any leaks.

Clutch slip from too much torque is also a cause but you're nowhere near the limits with MHD stage 1. The DCT can hold about 600nm in standard form and over 700nm with an xHP transmission tune.

Thanks, I have INPA but its setup for the e85. I have the e89 daten files but never got around to getting it working. Looks like this may be a good reason to. I assume it will store shadow codes for the trans same as other modules? I'll also see about checking for any leaks underneath.
Edit: Sorry, just realised I was confusing INPA with NCS. I don't need daten files for INPA so should be able to check as it is setup currently - can't remember if there's any additional setup for the e89, it's been a while since I've used it.

[enzed4]

Are you sure it's gearbox related?

The reason I ask is a friend had a similar problem, loss of power when a accelerating hard shortly after a remap. It turned out that the fuel injectors couldn't provide the amount of fuel the remap was asking for. His choice was either to upgrade the injectors or downgrade the map. It took a while to find it as it didn't happen every time, took it back to the remap garage and never had a problem since.

Wasn't a z4 but one to bare in mind.

This could actually be easy to troubleshoot - if I can get it to repeat the issue 'on demand', remap to stage 0 and see if it goes away. It would be just typical if it was the injectors, those and the coil packs are about all I haven't replaced in around 3 years of ownership
I am leaning towards a trans issue at this stage though.