BY Neil Currie It has been a while since I last sat down and wrote an article for the magazine but an interesting job came along recently so I decided to write about it. As always with every article I write, it highlights the importance of a solid process and test plan which is a must to fix complex vehicle faults on modern vehicles. This, along with access to manufacturer technical information meant the vehicle was soon diagnosed and back on the road for the customer to use. The vehicle in question was a 2016 Hyundai Santa Fe diesel which another garage had asked me to take a look at. The vehicle would start. However, nearly every single possible warning light on the dash was illuminated and an active bonnet warning message was displayed. In addition, when attempting to release the electronic parking brake to drive nothing happened. The garage then explained the vehicle was stuck at the customer’s house. It was parked awkwardly in their courtyard and could not be easily recovered. The customer had parked it up after arriving home one evening and then the next morning came out to go to work to find it would not move. Now as someone who loves a challenge I was intrigued and agreed to take a look at the vehicle. Although it would not be in the workshop, it was possible to gain full access to the vehicle and as long as it stayed dry all would be well. The garage had taken a look at it and carried out a global fault code scan. Only three control modules talked, which were the immobilizer unit, the A/C module and what Hyundai refer to as a CODE module. The fault codes that were stored all reported CAN faults so it looked very likely that we have a CAN bus fault with the vehicle. I got the registration number from them and did some homework before visiting the vehicle to be as best prepared as I could by studying the network topology and possible test points. Information A few days later I arrived at the vehicle armed with my information and test plan and set to work. The first step of my plan was to connect a break out box to the data link connector (DLC) of the vehicle. See Fig.1. This allowed me to have a test point to individually test all 16 pins on the connector and use a scan tool at the same time which made testing quicker and easier. My model also has lights which flash when activity is present, providing another good visual indicator of what is going on. For the scan tool to talk to the vehicle it needs to access the different networks on the vehicle or on its own diagnostic network bus so it makes a great first test point to see if we do indeed have a CAN bus fault. As I have mentioned in a previous article, some modern 26 AFTERMARKET NOVEMBER 2023 TECHNICAL www.aftermarketonline.net TAKE THE SANTA FE – DIAGNOSTIC – TRAIL A baffling issue with a Hyundai shows why sticking to a solid process is the route to diagnostic success vehicles now use a gateway module to connect all the different networks on the vehicle to each other which then is wired to the DLC so communication must be done via the gateway unit first. When looking at the CAN bus signals at the DLC you will only see a diagnostic bus which is only the scan tool and the gateway talking to each other. To access the relevant network, you would have to go to a module or accessible wiring section. Some manufacturers now use a gateway wired in parallel with the other control units and not a direct link to the DLC so you can test at the 16 pin port. This is why it is important to study the network topology as this will show how the system is laid out. On my vehicle no gateway was used so I could access the different networks from my breakout box and test there as a starting point. Upon connecting the breakout box and starting the vehicle to confirm the customer complaint straight away I could see a problem. On pins 6 and 14 we should see flashing lights and activity as this is the high speed network and is used for communication between the engine control module, ABS, SRS and on this particular vehicle nearly every other module fitted. In this case though, neither of the lights did anything. Confirming with a multimeter showed no voltage on both pins so now we had direction. The next question was “why?” Possibilities There are only a few possibilities as to why there was no voltage present. Either we had a wiring issue between the DLC and the rest of the network which may have split the
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