help Error Code - P029900 - A3 8V Saloon 135kw

[CerberusA3]

Have been getting this fault code for a little over 3 weeks, the car started by going into limp mode while doing motorway speeds (120km/h) you could turn it off and back on and it would fix it self. Then it started to do it on nation road speeds (100km/h) turning off an on again was a solution but was guaranteed to fix the fault, yesterday the car went into limp mode doing 30km/h and now is completely dead on power, I have changed the MAF sensor and no improvement, I’m told the code relates to a Turbo actuator fault but just checking if anyone else has had a similar issue before i pursue fixing the turbo. Thanks 🙂

[Steve Q]

I'd definitely say it's a turbo issue. Don't buy cheap Chinese turbos as they'll probs last just out of warranty. Go for a good quality one. 

[Sid2020]

I work on lots of different manufacturers so can’t say for sure about your exact model but the diverter valve is a common failing and usually the diaphragm inside it that fails and they throw fault codes typically to do with low boost or map/mad out of correlation, worth removing and doing a visual inspection

[Sid2020]

Map/Maf

just read my error 

[CerberusA3]

On 1/1/2025 at 4:14 PM, Sid2020 said:

I work on lots of different manufacturers so can’t say for sure about your exact model but the diverter valve is a common failing and usually the diaphragm inside it that fails and they throw fault codes typically to do with low boost or map/mad out of correlation, worth removing and doing a visual inspection

Checked the diaphragm in the turbo actuator and it was holding vacuum, i ran a turbo wastegate test and it only worked 2/10 times so possible the rod in the turbo actuator is broken? she's booked into Audi for a diagnosis next week (i know they'll tell me i need a new everything) i'll post once i know more 😀

[CerberusA3]

1 hour ago, Sid2020 said:

Map/Maf

just read my error 

Well i've changed both now so atleast i know it's not them 

[CerberusA3]

On 12/31/2024 at 6:04 PM, Steve Q said:

I'd definitely say it's a turbo issue. Don't buy cheap Chinese turbos as they'll probs last just out of warranty. Go for a good quality one. 

definitely agree, the cheaper you go the more problems your going to create for yourself 

[Sid2020]

Have you removed and inspected the diverter valve as different to a turbo actuator

[CerberusA3]

2 hours ago, Sid2020 said:

Have you removed and inspected the diverter valve as different to a turbo actuator

i was under the impression Diesels don't have diverter valves, could be wrong 

[Sid2020]

My apologies, for some reason I thought you had a petrol