Used MQB car check with OBDeleven

Check for clocked mileage indications, excessive wear symptoms, common mechanical faults, maintenance negligence in MQB-platform based and other VAG vehicles.

This writeup is based on my experience with Audi S3 (8V) and VW Golf MK7 (5G), but those methods should apply to other vehicles as well, depending on vehicle equipment and stored data.

Basic Faults Scan

As you expect - star with a simple full scan. This will bring fault codes from all the modules in the vehicle.

Do not clear found fault codes just yet!

B201A SVM Check

Some amount of fault codes is nothing unusual. For example fault code B201A - SVM check. in 0x5F - Infotainment is expected if someone installed Toolbox, updated navigation maps, flashed newer firmware of the infotainment unit.

Uxxxx fault codes

Uxxxx code can indicate that the module received a fault information from another module, that it relays on. So for that module it's a remote fault code. For example if there's an issue with one of the wheel speed sensors connected to the ABS module, the ABS module will have the "master" fault code, and all other modules that relay on vehicle speed data provided by ABS module, will have Uxxxx fault code stored.

Another thing that can trigger Uxxxx code is not properly configured module. If coding/adaptation was altered, module was replaced, or other module is no longer present in the car, it can cause a "missing message" fault code. It simply means that module is expecting some information from other module but it's not getting it.

Mileage Confirmation

Freeze Frames

When a fault code is triggered, there might be a related freeze frame stored with conditions details from the moment that fault code appeared. Although this data is intended to help troubleshoot the fault, it might also contain vehicle mileage information.

DSG mileage vs Engine mileage

DSG / S-Tronic / PDK gearbox mileage details can be found in TCU Live Data. Compare ECU and TCU mileage.

Module 0x02-Transmission → Live Data → Current vehicle odometer reading

Module 0x02-Transmission → Live Data → Transmission mileage

EA888.3 TSI/TFSI Timing Chain Stretch

1.8TSI/TFSI and 2.0TSI/TFSI engines that you know from VW Golf MK7 (5G) Alltrack, GTI, R, Audi A3/S3 (8V), Skoda Octavia MK3 (5E) RS, and many other VAG vehicles have a timing chain which wear can be estimated from engine live data. Actually, ECU is estimating it itself, most likely based on the readouts from crankshaft and camshaft sensors.

Module 0x01-Engine → Live Data → Camshaft adjustment intake bank1, phase position

Module 0x01-Engine → Live Data → Camshaft adjustment exhaust bank 1, phase position

from 0.00 to -1.00 = perfect readout
from -1.00 to -4.00 = expected in a used vehicle
from -4.00 = chain most likely stretched and should be replaced/

Freshly replaced timing chain should report value between 0.00 and -1.00.

Based on user reports, every ~20k miles / 30kkm adds -1.00 to the camshaft phase position. For example: value -2.75 would indicated asdf of mileage 55k miles / 82kkm.

Chain that's stretched beyound a single tooth (jumped a tooth) will show value beyond -5.86.

There's much more reliable way of checking the stretch, by looking at the chain tensioner. TODO

0x5F display operating hours

It's safe to assume that the infotainment display is on pretty much all the time when the engine is on. Display Unit stores its operating hours counter, which can be view in Live Data of the Infotainment System.

Module 0x5F-Infotainment → Live Data → Multimedia display unit 1 → Operating hour counter

Based on that readout we can estimate a rough mileage of the vehicle. For example, readout of 1500h can be multiplied by an average speed of 40mph / 60km/h. This would give an estimated mileage of 60k miles / 90kkm.

Notice: 40mph / 60km/h is an average speed in mixed conditions. For urban conditions I use 20mph / 30km/h, and for highway conditions 60mph / 90km/h.

Notice: if at some point display unit was replaced with new one (warranty repair) or used one (MIB retrofit), this calculation will not be valid.

Common Faults

EA888.3 TSI/TFSI Camshaft Adjustment Actuators

Camshaft adjuster is driven by oil pressure and and controlled with an magnetic actuator. Both intake and exhaust actuators are the same, and can suffer from the same issue, which is slow reaction causing idle RPM fluctuations, misfires, or even engine stall.

In ECU live data you can find specified and actual positions for both camshafts. By comparing specified and actual position, you can check if the adjuster is working correctly or not. You can check the difference on various RPM, but on idle it will be visible the most.

Exhaust side

Module 0x01-Engine → Live Data → Camshaft adjustment, exhaust, bank 1, specified value

Module 0x01-Engine → Live Data → Camshaft adjustment, exhaust, bank 1, actual value

Intake side

Module 0x01-Engine → Live Data → Camshaft adjustment, intake, bank 1, specified value

Module 0x01-Engine → Live Data → Camshaft adjustment, intake, bank 1, actual value

In a correctly working engine, the difference between specified and actual should be ±1.00°. If the difference is reaching ±5.0° or higher, it will indicate failing actuator or failing adjuster oil valve.

EA888.3 TSI/TFSI Thermostat Actuator

TODO

EA288 Diesel water pump shutter

TODO

Front Radar (ACC, PreSense, FrontAssist) misalignment

TODO

Heavy Usage and Neglected Maintenance Indicators

ECU and TCU Flash Counter

TODO

Over-rev and Over-temp memory

TODO

Misfires counter

TODO

DSG drive strategies

TODO

Gateway drive modes counter

TODO

Launch Control counter

TODO