21 Jun 2024
The voice of the independent garage sector

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

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.

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 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?”

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 network so it could not talk back and forth. Alternatively, we had a short to ground pulling both circuits low causing the lack of signals. This could be quickly proven with one of my favourite tools, a test lamp. If I connect my test lamp to battery positive and connect to each pin one at a time and they are indeed shorted to ground my test lamp will light as the ground will complete the circuit. If they don’t, I most likely have a wiring issue which can then be tested with the multimeter.Using a test lamp is a safe way to do this as the bulb limits the amount of current flow allowed to flow in the circuit. Connecting my test lamp up to pin 16 on the breakout box and one at a time to pins 6 and 14 lit the bulb showing I did indeed have a short to ground and the cause of all the issues the vehicle was experiencing. Pin 16 is battery positive, which makes a handy testing spot saving running cables out to the battery itself.

With this information I had now confirmed the network fault and could then set about tracking down the cause. This is where having the network topology and wiring diagram connectors was a must as I could split the circuit into chunks and test a piece at a time to narrow down the fault. Studying the diagrams showed several connectors inside and outside the vehicle. I decided to start with one near the front which would eliminate the wiring and modules under the bonnet. Leaving my test lamp connected allowed a good visual indicator if I removed the short from the circuit. I just had to be careful I didn’t unknowingly open circuit the wiring to the DLC which would also put the light out and lead me on a wild goose chase.

Diagrams again
Splitting the circuit at each test point one by one did not make any difference so it was back to studying the diagrams again. I then found a point in the diagram labelled license lamp. Like me, I am sure you are thinking what has a license lamp got to do with the CAN bus system? I decided to look into this and upon opening the connector information it showed the rear view camera in the tailgate used the high speed network. Why it was labelled license lamp I do not know. I guess that is a question for Hyundai. The technical information showed a connector at the rear of the roof lining very close to the rear interior lamp. After looking at what was involved to gain access to the camera itself, it was quicker and easier to drop the roof lining and disconnect the multi plug there. Upon gaining access and removing the connector my test lamp had now gone out. Please refer to Fig.2. Bingo! I had found my short.

Restarting the car and checking my breakout box I now had flashing lights on pins 6 and 14. Connecting up the scan tool and attempting a global fault scan, I now had full communication with the entire vehicle, which allowed all the fault codes to be deleted and cleared the dash of all the warning lights. Trying the handbrake, it now released and it was decided to drive the vehicle back to the workshop to access tools to remove the interior tailgate panel to carry out the final tests to confirm the camera was indeed at fault and it was not a wiring issue. Upon removing the tailgate panel and exterior plinth to access the camera itself, it transpired that the camera was badly corroded and wet having suffered water ingress. Please refer to Fig.3.

Reconnecting the wiring loom and disconnecting at the camera connector showed communication was still present, I then checked wiring at the connector and found everything to be as it should proving the fault was within the camera itself.

In the end it was the rear camera shutting down the car, preventing it from driving. Interestingly, the engine started and ran so this must be due to the way Hyundai have configured the network as with some manufacturers this does not happen. I have also noticed that other manufacturers run the camera on a lower speed network so if this happened the vehicle would still be usable. It would just display different symptoms such as blank reversing screen or a fault message on the dash.

This job shows that a seemingly complex fault can be simplified down in to bite-size chunks with a solid process, test plan, manufacturer technical and wiring information, and then quickly and accurately diagnosed.