Recently, I got the check engine light and the truck started stalling intermittantly. I went to diagnose it with my AutoTap software only to find out the OBDII port was dead. The circuit is tied ot the interior light circuit. The fuse was blown and I checked everything I could for a short to no avail. I took the truck to a dealer and they said they replaced the fuse and fixed the engine light with a cam positioning sensor. The fuse blew right after I left the dealer and I was wondering how they got the port to power up for ashort time - Thank you for your help!
I don’t know how they may have made it work but I would take it back and tell them to fix it with no additional charge. I do believe they have some kind of warranty on their work, don’t they?
They made a point of stating they only put a fuse in and it magically worked. So there is no recourse on the repair of the short. They charged me $450 to put in a Cam Positioning Sensor. I have some major reservations about that. My fears of dealership ripoff have been realized. I am just wondering what they did in order to get the OBDII port working long enough to diagnose the problem.
The trouble may not be a dead short but something may be drawing a sufficient amount of current to cause a delay in the fuse to go out or there is an intermittent shorting problem. An intermittent problem could be hard to find.
The trouble may be in the light circuit but it could be elsewhere. I would get the service data for the wiring and find out all the areas the fused circuit ties to and then check suspected trouble spots for a problem. You may have to disconnect some non-critical areas one at a time to see if that eliminates the short.
I started searching for the short by inserting a 30 amp fuse - blew immediately. I used a VOM to check ohms while I unplugged everything in the circuit. I found nothing wrong. I am leaning towards the junction block or the management box in the kickpad. What I was wondering is - how did the dealership get the port to power up for a short while? The fuse blows immediately again and the dealer won’t tell me what they did to get the port to work. There is some sort of trick involved. I dont care about the short so much in the interior lights, I care about using the OBDII port to diagnose the engine light problems if they occur again. Thank you!
Maybe they used a self-powered scanner?
I dont know if there is such a thing - but they did have the interior lights working for about an hour after I left the dealership. So they did something to temporarily correct the circuit problem so they could use the OBDII port.
I assume that the 30 amp fuse that is blowing out supplies power to both the OBD2 port, the interior lights, and other things. You stated you checked the circuit and found nothing wrong with it but yet it blew the fuse instantly before you did the testing. If all this is correct I would have to say the trouble is intermittent since the lights worked for a while after you picked up the vehicle. You are going to have to isolate the power to suspected trouble areas that the fuse ties to and see if the trouble goes away. If you don’t have a wiring diagram and are you are going to work on this yourself I suggest you get one since it will be a big help in showing you where to look for the trouble.
If the fuse still blows out when you replace it after your testing then something in your testing proceedure isn’t right.
I did get my hands on the wiring diagram and I can’t seem to find the source of the short. The dealer did something to allow the interior lights to work for a short period of time. I am trying to find out what they actually did. There is some sort of workaround to allow the OBD port to power up. Thanks for your input.