Electrical system restricted

christinescoms said:

Hello everyone.

We have a bit of an odd intermittent warning. Now and then (which seems to happen more often in the cold), we get this alert message. It remains until the next start when often it disappears.

I can drive hundreds of miles between it occurring and then sometimes it happens almost every morning for a few days then is gone again.

The dealer took it for a week and gave us a loan q4 and it didn’t do anything for them. Not could they see anything in the log. This morning it pinged again and I took it to them.

They plugged in straight away and eventually came back with an error: “Communication issue with front motor”. It’s a 40, so doesn’t have a front motor!! https://alzaabiautocare.com/blogs/crucial-regular-car-maintenance-for-your-electrical-system/

Click to expand...

thanks in advance for any help

Reading between the lines, I assume that it's a fault on a car. However, it would be good if you could confirm that and say what car it is, and what type of engine (and gearbox if applicable) it has.

How do you expect us to analyze so little evidence, when the Audi dealership was stumped. There seems to be something in your over-night environment that is driving it nuts. Charger? Wifi ? Security log? Moisture? Sensor glitch?

"No communication to a non-existent front engine" is just illogical.
Do you have any other concerns or info?

Audi offers the 2024 Q4 e-tron in two versions: Q4 40 e-tron and Q4 50 e-tron. Each uses an 82-kWh battery pack. The Q4 40 e-tron employs a 201-horsepower electric motor powering the EV's rear wheels. It offers an EPA-estimated 265 miles of driving range. The Q4 50 e-tron adds another electric motor to provide all-wheel drive and a more robust 295 horsepower.

It might be worth checking the state of the 12 V battery.

When the car's not in use, the DC-DC converter isn't on, and the 12 V battery is the only thing keeping the 12 V system going. At the point where the car turns on, lots of electrical devices start taking power and if the 12 V battery voltage drops, one or more of them can be slow to turn on. Then you get other devices raise DTCs for communication issues for the signals that were expected but were missing.

Of course, the DTCs for low battery take longer to register, and the DC-DC converter is on before that can happen

I've had faults on an EV when starting up that pointed to brake errors. It was only because I had a non-standard logging system on the 12 V battery that I realised that the 12 V battery was weak. When I realised that the 12 V battery was weak, I didn't bother looking deeper into exactly what had happened, but I changed the battery and the faults went away.

I've even had brake warnings come up as the first indication on an IC car when the alternator died.

We've all got years of experience of IC cars having 12V batteries go flat, and the symptoms flat batteries cause. EVs have completely different symptoms when the 12 V batteries die and we're only starting to recognise those symptoms.

The Electronic Control Unit (ECU) might have a bug or require a reset. The dealer should be able to reflash or update the ECU firmware.