dalathegreat

Hi,
I run a small EV repair shop, and a Q5 owner contacted me. This vehicle got this error message:
Hybrid drive: system fault. Power steering and brake servo possible failure.

The service center tried to find the issue, and recommended these replacements after 16.7h of diagnosing
- Both 12V batteries 690 €.- Hybrid battery for around 12,000 €.

The fault codes:

• 042A6 [17062] P0A1F00 Akkuenergiahallinnon ohjainlaite X
• 03054 [12372] P0A1B00 Tehoelektroniikan ohjainlaite, sähkökäyttö X
• 035D9 [13785] P0AB900 Hybridikomponentit järjestelmävika X
• 0358E [13710] P0B3C00 Hybridi-/suurjänniteakun jännite, anturijohdin 1, Epäuskottava signaali X
• 03590 [13712] P0B4100 Hybridi-/suurjänniteakun jännite, anturijohdin 2, Epäuskottava signaali X
• 03592 [13714] P0B4600 Hybridi-/suurjänniteakun jännite, anturijohdin 3, Epäuskottava signaali X
• 03594 [13716] P0B4B00 Hybridi-/suurjänniteakun jännite, anturijohdin 4, Epäuskottava signaali X

Google doesn't help much here, but can it really be so that a battery replacement is the way to go?

apoelistas

Hybrid battery for around 12,000 €.???

Is there a mistake?

I think Toyota and probably few other Man. only replace the cell that fails. Does Audi replace the whole unit?? Isn't that excessive?

A question. What is the value of the car?

MP4.2+6.0

Given cost/benefit, look at age of the "regular" batteries. There are two for hybrids, as noted in passing in first post. One is a very generic Audi/auto conventional size/fitment. The other (small) one is more specialized--sort of like a big motorcycle battery. If they are more than 5 years old, I would replace both. They will eventually fail anyway and are relatively simple to replace. My 2013 was starting to fail per routine dealer service check in early 2020. You do have to take apart some of load floor to get to the larger relatively standard one.

On battery hybrid pack, way more talked/worried about than ever done. In USA there is a very long warranty on them. Check the local country warranty coverage specific to hybrid battery pack if you still think this is the issue. I doubt it.

Koura

No mistake here. Car was worth ~22000€ before this system fault, 120000 km driven.
Both 12 V batteries were tried (replaced) but it didn't help. They would be about 700€.
So next fix would be replacing whole hybrid battery which would cost about 12000€.
And yet we wouldn't be sure if everything is ok. If not Audi's official service suggested that after that we know if we should also replace power and control electronics of the electric drive.
If that too has to be replaced, it will cost around another 12,000 €. So maybe 26000 € fix to 22000 € car. Sounds reasonable, uh?

apoelistas

Can you disable the hybrid drive?? in case it is an option and you are certain it is not a relay or a fuse or a cut wire or a faulty control module or a solenoid ...

if you want to give a shot of fixing it start with low cost parts, control modules etc . The hybrid battery has 8 years manufacturer warranty. Is it not covered?? I would assume that with your mileage it will last longer. Is there a charge reconditioning procedure for hybrid batteries???

If you assume battery is good what are you left with?? Sometimes one reason arises because there is anothe fault.

i would have tried to see what vcds recommends for these two first. Click on them and see recommended actions.
03054 [12372] P0A1B00 Power electronics control unit, electric drive X
035D9 [13785] P0AB900 Hybrid Components System Fault X

VCDs gives recommendations right??

Steppenaudi

The first four errors are Battery Energy Control Module, Drive Motor A Control Module, Hybrid System Performance, and Hybrid / EV Battery Voltage Sense "A" Circuit Range / Performance static. I can't find definitions for the last three from Google or a 2013 Q5 Hybrid repair manual. By the way, VCDS doesn't give service recommendations.

As far as I know (and I own a 2013 Q5 Hybrid) there is only one 12 V battery. I can't find any mention of another 12V battery in my vehicle in the service manual.

I haven't had any problems with my Audi Q5 Hybrid 12V battery, but I'm up to 7.5 years on that battery. I would expect it to start being a problem just because lead-acid batteries don't last forever.

I would recommend getting the 12V battery replaced with an Audi-sourced battery, including coding the new battery to the vehicle. I've had some years of experience with a Prius, and that vehicle will start acting badly & show reduced mileage if the 12V battery starts to die. Clear all the error codes after replacing the battery and see what happens. If the error codes reappear, then further work may be needed.

Also, I would ask if the gas engine is working OK? No mis-behavior like missing/misfires? I've found that on my Q5 Hybrid, if the gas engine develops a misfire and starts running rough, the Hybrid System Performance warning light comes on on the dash display. Nothing is wrong with the hybrid system, but it seems to be very sensitive to the gas engine's running condition.

apoelistas

• A reminder
• After replacing batteries you have to code them. Then battery power management resets it self as mentioned above.

MP4.2+6.0

There are two, as I stated. I have replaced them first person. 2013 model. Added battery is mentioned in perhaps the old Hybrid drive/intro SSP.

First one--the conventional auto type--is under the floor in back, buried under a bunch of main (lithium) battery pack cooling HVAC ducting stuff. Hard to even see it until you take off a few plastic duct pieces. To access, you remove the four tie down brackets, pull the safety kill switch on the main hybrid battery pack, and then remove that whole load floor panel in one simple move. The other motorcycle looking small one is behind the fender trim in the back cargo area on the (USA/Continental Europe) driver's side. Remove that left side cover and look toward the fender slightly forward and you will see it. That one is the one that first generated a code on mine during routine service. I changed both.

Steppenaudi

Well, I had a journey of discovery this afternoon. I took the rear cargo area floor off my Q5 Hybrid and started hunting for the extra 12V battery you described. I finally found it (its ground lug at least) buried under the Battery Cooling Module. The battery itself is not visible from above. Up to now, I thought the 12V battery in the left cargo compartment wall was the only 12V battery, like in a Prius. So, if one wants to work on the vehicle without the "battery" connected, one has to remove the Battery Cooling Module to get to what the Audi repair manual refers to as Battery -A-. Battery -A1- is the left side battery, and Battery -A2- is the Li-Ion (Traction) battery for the hybrid.

I'm mystified now about why Audi put two 12V batteries in this vehicle. In a Prius, the 12V battery starts the electronics, which pull in the contactor for the traction battery, which starts the vehicle. The battery doesn't have to be very big. One regular 12V battery should be sufficient for both electronics start-up and engine start in my vehicle.

From the Audi shop manual I have, it seems to be relatively easy to remove the Battery Cooling Module, though it at first glance it doesn't look easy to remove. Disconnect the clip-on ducts, remove four nuts and supposedly lift the unit out and set it on top of the traction battery, The manual says to put a drape or towel across the traction battery before resting the module on it.

Component layout under Q5 Hybrid cargo floor looking forward.

Looking down along green arrow in previous picture. Neg battery terminal is slightly out of focus.

I didn't actually try it. There are freon lines and wiring bundles running to the Battery Cooling Module. They make me skeptical about how easily one can move the module aside.

Also, there's an engine starter motor. I had thought that the Q5 hybrid system electric motor (replaces the torque converter) started the engine (like on a Prius). That would help explain the existence of Battery -A-.

Steppenaudi

Just for the hell of it, I went out and checked the quiescent "12V" battery voltage at the jump stud under the hood. I see 12.2V, which isn't great. I drove the vehicle earlier today, so the batteries should be > 12.5V when healthy. So it goes.