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).