Case study by Gareth Davies AAE FIMI, Euro Performance

A mystery involving a remap history

Vehicle: 2017 Audi A6 All road 3.0 TDi Quattro CRTD engine code

Problem: Lack of power, poor running, no warning lights on the dashboard

Being a brand specialist can make life somewhat easier in the workshop. It’s only natural you will see a higher repetition of cars presenting the same faults and you can often go through periods saying, “it looks like it’s another one of those”. These are not born out of complacency and applying the correct process will always apply. However, on the other hand, there are an increasing number of occasions where you are sought out by the consumer because no one else has been able to help. No, we don’t survive as soldiers of fortune because we escaped from a high security military stockade for crimes we didn’t commit… We exist because of our backgrounds, our chosen brand specialism or, maybe, just because we have a reputation for being able to help, when seemingly others can’t.

In this case study, the vehicle in question was a 2017 Audi A6 All road 3.0 TDi Quattro, CRTD engine code. It was booked in with us after a visit to the local Audi dealership. At the point of enquiring, I was asked by a front of house colleague if we were able to help. The dealer had advised the customer because the car had been re-mapped (a process whereby the engine ECU software is modified to improve various factors such as performance and fuel efficiency) they would not be able to help. I agreed this would be something we could help with, and he was duly booked in. Ten days later the vehicle came in and the customer completed the fault assessment questionnaire. The notes described a lack of power, poor running, but no warning lights on the dashboard.

I began with busting out the big and shinier laptop than other independents (ODIS) – after all, that’s usually why they end up with us specialists, purely for a better laptop… Whilst it was loading up the vehicle ID and carrying out a fault code scan of the car, the customer had kindly left some documentation with his questionnaire from his dealer visit. The logs showed communication between a technician and the mother land (Milton Keynes, the halfway house to full blown mother land). They had requested technical help as they were unable to shed light on the issue. The technician was advised the engine ECU software was modified and as a result, this would need to be corrected before proceeding further. It’s likely that a commercial decision was made by the dealer not to move forward, which is fair enough. If it’s not their type of work, that’s understandable.

We had completed the scan and as far as fault code entries went, there wasn’t much to go on. There was a sporadic entry in air suspension for ‘compressor shut off’, the type and nature of fault is what is left behind after jacking/wheel change mode, and there were no issues visually with the air suspension set up. It was apparent quite quickly that the car was very unhappy. The technician who had kindly brought the vehicle around into the workshop for me whilst I had been finishing talking to a customer, reported in good old fashioned Welsh terms ‘that car is proper unhappy butt’. I found this interesting, given at this point I hadn’t run the engine, merely connected a battery support unit and was using ignition only. I started the engine. It was apparent very quickly, he wasn’t lying. The vehicle would start, it took a little longer than normal to catch, and when it did, it ran very badly and cut out almost immediately. If you persevered a few times, and then introduced some throttle whilst running, it would begin to improve to a steady(ish) idle.

Rarely would you expect such a dramatic and obvious presented symptom, without any fault code entries, of any kind. Most importantly, ones that may indicate as to why the engine was so grossly unhappy and cuts out. Basic live data checks revealed nothing concerning; fuel pressure was a plenty and a relative compression check was also acceptable. Before getting too deep, I consulted technical service bulletins. There were a lot, but none that directly fitted my symptoms, particularly with no DTC entries.

Now, I suspect some of you are reading this, and like the pantomime ‘he’s behind you,’ are screaming “It’s the map, it’s the map!” Well okay, there are factors in the map that could be attributing to the issue, but some good datum points I always like to check before assuming anything would be:

The customer has owned this vehicle for a significant period and was not aware of any map on the vehicle until the dealer made him aware. He admitted the car went ‘like a top’ and whilst the 3.0 272 engine is a real delight, it may have gone very well in this customer’s case.

The Map, if bad, would have had to develop a bug, or change something that’s now critical to correct and harmonious operation, that it wasn’t doing before. This could in theory be something like the car was mapped to remove DTC entries for a faulty component, and this component wasn’t blanked or dealt with correctly and now has allowed the change of state so to speak. Yes, this is valid, but again, case in point, would be a 54k miles 6-year-old high end Audi, that overall doesn’t look like it has wanted for anything so far in life? It doesn’t really fit the suit but still could be a possibility if we remove the emotion.

So, with seemingly not a lot to go on in terms of evidence or clues, I listened to the cranking and first start procedure from the engine bay, while an assistant cranked and fired the engine. This was a useful step. I noted that the engine appeared to be a little strangled; almost like it couldn’t breathe. I’ve sometimes found the simplistic, oldish school approach to diagnostics can work wonders, before wading in too deep. I removed the air filter Assy and ran the engine again. It was notably loud, louder than this engine should be (I ran a 3.0 CRTD A6 for four years and loved it). These engines, like a lot of EU6 derivatives, suffer quite badly in terms of emissions control restrictions and blockages. It seemed worthwhile to break out the borescope camera to check the inlet tract. This may seem beyond the desired non-intrusive test methods, and what exactly is covered by the assessment, but could be achieved quite quickly by removing the charge hose to the throttle flap and sending it up the inlet tract. My rational on this occasion was that it had been to a dealer, and another independent before this, and the testing I was carrying out was unlikely to use all the 1.5 hours set aside for the assessment fee. I also wanted something to be able to go on, an angle, a clue.

The borescope inspection showed there was significant soiling to the inlet tract. I also performed an output test on the inlet throttle flap with the camera in place and was unable to reach end stops due to the fouling. Given that we strip enough of these on a regular basis for ‘in the valley’ component repairs, I stripped it for a closer look to be sure. Figure 1 shows significant carbon build-up around the inlet throttle flap, and it also showed on inspection it was not able to reach end stops or hadn’t for some time. Now the further thought at this point was, if tampering had occurred in the remap, of which there was no detail at all by whom, or to what level, as the customer was unaware, then it could be that it had, or other components had, been removed or modified to not work as expected. Figure 2 shows the gas movement around the soiled component.

At this point, I advised the customer of where I had got to and where I would need to go to move forward. I advised the best course of action was to clean the affected carbon, reevaluate the state of running and road test, if possible, to understand if a residual complaint was present or if, in fact, the issues were fixed. I also suggested that if they were not, and we need to move forward, we may need to flash the car back to standard to continue troubleshooting. Fortunately, as Authorised Avon Tuning agents, we knew we would be able to put him back in a ‘tuned’ state should he so wish, after we had concluded any other repairs that may be required.

In terms of best practice, I set our stall out early on. I advised of all likely best- and worst-case outcomes and the associated costs involved, and the customer was comfortable with the plan. I did also have the option here to bench the engine ECU and send the file off for assessment by the wizards at Avon tuning, should I need to. Then they could give me clarity on what had been done to the engine ECU software in detail, such as component modification or deletion.

With all the carbon cleaned, I reassembled the inlet Assy and started the vehicle up. I had an improved outcome, the engine would now fire willingly and run without trouble. It also sounded audibly quieter through the inlet. With VCDS on the passenger seat, and a wry look about me, I prepared to go for a post repair test. The test lasted approx. 2/3’s of a mile before the car hit a brick wall in terms of performance. Zero go whatsoever, did not want to change up the gearbox or make any kind of progress. Hmm, not so simple then. I pulled up, confirmed by restarting the experienced symptom was corrected, it was. And for another 1/10th of a mile after restarting it had a lovely amount of zest about it, followed by horrendous limp home and under 30mph all the way back to the garage.

After reevaluating the situation, there were still no DTC’s and all the important live data looked good, I needed another line of enquiry. I checked the advanced ID section of the engine ECU, Figure 3, and I couldn’t understand why the flash counter was so high. Maybe it had received software updates in a dealer and then with the tune on top at a later date… maybe? At this point I was satisfied I wanted to flash back to standard. What on earth could be making this car so underperforming, that doesn’t show up on a mod file?

Fortunately, we offer tuning, so there are various tools that can allow flashing back to standard, or RTO. I applied the software, which completed fine. I started the engine and still had no DTC’s or warning lights. I repeated the road test route and sure enough, very quickly the car limped. This time, however, I had an engine management light and a DTC to work on.

The DTC entered was P102B and this related to an engine oil temperature sensor, Figure 4; this engine variant had more than one. I located the (single wire) sensor and managed to retrieve the live data for it and found it was implausible, Figure 3, given the car had been running for a short period of time. Upon physical inspection of the loom, I noticed a small discoloration to the insulation on the harness and could get the temperature to change nominally when wiggling the tightly routed harness, Figure 5. Suspecting the discolored section of harness, I removed the insulation and it was evident that at some point the harness was shorting to ground across the front of the cylinder head. The temperature sensor in question is one that we frequently see failing, and a bit of a potch to get to.

I shared my findings with the customer, and advised on the repairs that should be carried out. This would be to repair the section of harness, reinsulate and reroute, moving away from the cylinder head bracket. To replace the oil temperature sensor, given its nominal cost, and retest the vehicle in standard software state. If all of this went to plan, he could then have stage 1 software applied afterwards. He was happy with the plan and let us carry on.

With the wiring repaired, sensor replaced, and the harness more suitably routed, faults were cleared, and I carried out a road test. I logged various data PIDs to see how the vehicle behaved. I was pleased I was able to conduct a road test without limp home mode and saw a nice uniformed and linear increase in oil temperature readings via live data from the two oil temperature sensors. They were mostly within 0.5 – 1.0 degrees Celsius of each other the whole time, Figure 6. This also served as a great pre tune safety check log evaluating boost etc. The car performed well, and I was happy we could safely apply the tuned software.

A second road test was carried out after the software upgrade. These engines respond really well to tuning, and the delivery of torque was lovely – it felt nice to drive again. The customer was very pleased and after a few weeks of using the vehicle left a super review for the garage too.

Very often, jobs come through the doors and you really don’t know how they are going to go and what they are going to be. I think it’s important to always take the same approach, whether the outcome is a simple bulb or fuse, or something more complicated such as the above. Setting out realistic outcomes versus spend, and the time required to get to those conclusions or stages is vital for the customer, and for the garage/technician. After all, it must be fair, timely, but most importantly, suitably remunerative for the skill and effort involved.

Thank you to Alldata and Avon Tuning for their assistance throughout this job.