I was called to a shop to do a post-repair scan on a 2019 VW Golf (Figure 1) that was all finished and ready for delivery. This shop is a high-volume shop, and they move many cars in and out of the door and they make it their own policy to scan all cars when they are done just to get peace of mind knowing that vehicles are safe and free of any issues prior to releasing the car to the customer. The shop may not always get paid by certain insurance companies for doing post-repair scans, but it is to their benefit to prevent a comeback and an inconvenienced customer that may give bad feedback on the shop’s services.
When I arrived at the shop, the car started up fine and the only warning light that I noticed on was the yellow triangle caution sign (Figure 2). This was because I did not have my seatbelt latched while I was sitting in the driver seat. This caution triangle is commonly used by manufacturers to alert the driver to view the instrument cluster to look for issues with the vehicle prior to driving off down the road.
As I performed the vehicle scan, I came across 10 control modules with about 32 faults combined (Figure 3). Most of these faults were no longer present and were generated from the accident or during the repair of the vehicle. It is highly important to record all of these faults in your post scan prior to clearing the entire vehicle. It is equally important to put the vehicle through three key cycles to see if any of these codes return. After another full vehicle scan, there were four control modules with active “U” codes in memory for a module not responding on the network. It is not uncommon for other controllers within the network to not report an issue such as this because they may not rely on the missing controller for network data for them to function.
The Gateway Control Module is the main control module that overseas network communications and this was the only module of the four control modules that actually specified the module at fault. The Gateway Control Module stored an active code U104500 that failed the Lane Change Assistance module for not responding on the network. This was odd because there was nothing reported to the instrument cluster to alert the driver of the vehicle at start up. This is very important to know because if there is a control module that is low on the totem pole, the network doesn’t have to report a failure of the module back to the instrument cluster. Therefore, many onboard issues may go unnoticed until a customer comes back with an operating issue. A lot of vehicles will use a tier-rated priority to qualify if the instrument cluster needs to report a failure in the network. So as a quick check of the Lane Change or Side Obstacle System, shops need to view both warning lights on the side-view mirrors at start up. If the LEDs do not light up or both go on and stay on, then there is a problem with the system. At this point, I went ahead and started the vehicle and sure enough the Lane Change icons in both mirrors were inoperative (Figure 4).
This definitely indicated to me that the system was not operating at all. I now instructed the shop to pull the rear bumper so I could examine both rear Lane Change modules and the harness for issues. The left rear module was the master module and controlled the slave module on the right side of the vehicle so I was more concerned with checking the left rear module first.
The shop quickly pulled the bumper assembly off of the vehicle (Figure 5). I visually inspected the connector on the left side and verified the wiring identifications using a diagram from my information system. There were seven wires of which two were power abd ground feed, one LED control to the left side mirror, two CAN lines for the network and two dedicated CAN lines routed to the right Lane Change module to communicate with the left Lane Change module (Figure 6).
I went to remove the connector from the left module and it basically slid off very easily without pressing in the connector lock. The connector was never fully seated and locked in place, and this was the whole problem. I pulled off the connector and closely inspected the lock to make sure it was not damaged. This was a newly installed harness and it was the spring action of the new grommet in the connector that made it hard to click in place (Figure 7).
I reinstalled the connector and started the vehicle and now you could see the indicator on the side view mirror was now working (Figure 8). But I had a new problem. The LED in both side view mirrors were staying on constant without shutting off.
It seemed odd that this vehicle would have a second problem when I had already found the problem. I instructed the shop to leave the bumper off until I scanned the vehicle again to check for further issues. I went back to my scan tool and scanned the entire vehicle again and was able to pull two codes out of the Lane Change control module. The codes stored were 1310721 and 1572868, but there were no code definitions for these codes other than “Unknown Error” (Figure 9). The code number is always stored in the vehicle, but it is the job of the scan tool that provides the definition of it. This fault basically was unidentified because the code library in the tool was not updated yet with the 2019 code list, so it could not properly tag a definition to the code number.
Luckily for me, I have the dealer tool and made the investment to register myself with VW/Audi as an aftermarket dealer tech and I am registered through their security professional database. I placed my VW/Audi ODIS System on the vehicle and pulled codes out of the Lane Change module. These codes were for a control module not programmed and parameterized (Figure 10). These were two separate procedures that had to be done with my dealer level tool. The shop had replaced the left rear Lane Change module with a new one and thought it was just s plug and play module and they were unaware if there were post procedures to be performed on the new module. So I now I had to perform the task of setting up the new control module to finish this vehicle and get it delivered once and for all.
There are many lessons to be learned with this post-syndrome vehicle. There is no guarantee that any vehicle is in perfect order just because there are no lights on the dash. You may want to think twice about post-repair scanning your vehicles for your own investment whether you get paid or not, because there may be many unforeseen issues that may not arise until the vehicle is in the owner’s hands. A lot of control modules on these vehicles today may be plug and play, but it is your duty to find out for sure before the vehicle is released. Some of these replaced modules may just need post procedures performed without programming software once they are changed, and this can be solely done with a scan tool through simple set ups such as calibrations.
Last and most importantly you need to really use your five-sense diagnostics and just make sure things are properly put back in place. Use your eyes, for visual inspections, use your hands to feel things as they slide in place for binding, use your ears to listen for clicks when things lock in place, use your nose to smell for burnt components or fluids leaking, taste is an option at this point. This may help you to prevent unnecessary comebacks down the road. Don’t be that guy plugged into a smartphone with a headset while working on a vehicle because you will lose all of these human sensors at your own disposal. Hope this story has enhanced what you know or didn’t know and possibly hit home with a lot of the readers out there.
