I recently had my 2007 G35 coupe 5AT get a new engine (nasty rod knock). After the shop finished the swap everything on the car worked perfectly except the OBD2 port has no power. The guy at the shop said he was able to power it up externally but never mentioned how. I have been trying to figure out the issue for about a month now and haven't found any information. I can't even find which fuse is responsible for the OBD2 port. My cig lighter works (which I heard runs on the same fuse as the OBD2). I'm going to need to get the car smogged soon so any help will be amazing.

 

No it's not tapped off the cigarette lighter, that is it's own circuit. I think it's fuse 89 in the IPDM, 10 amp.

 

That fuse is labeled as "Data Link Connect, Starter Relay". My car starts up ok, is it still worth checking that fuse?

 

Fuse 89 only supplies power to part of the starting circuit on the 6MT equipped vehicles (it's also the power for the clutch interlock circuit). On the 5AT it doesn't affect starting, I would check that fuse.

 

Sorry for such a delayed reply, I got caught up with work. I tired to swap that fuse out with one that I knew worked, still no power to the OBD2 port. Is there anything else I should check?

 

Fortunately it's a very simple system, here is the wiring schematic. I would probe the pins listed with a DMM to see if you are missing power on one or both of the power leads to it. Also probe for continuity to ground on the other two ground pins.

Looks like there is also another fuse #34 that powers it, I thought it was just fuse 89 but you should check fuse 34 also. Pretty sure that fuse would be coming from the IPDM as well.

 

Nope looks like I was wrong, fuse 34 is on the fusible link and it's only purpose is to supply power to the diagnostic port, that's probably the one that blew.

 

Fuse 34 appears to supply power (unswitched) to the DLC as well, but it's also for the ECM, so if that fuse was blown I'd imagine your car wouldn't be running. I think you have a bad wire or connection somewhere.

I'm curious about a couple of things - does your SES light work (illuminate during bulb check at start up)? How exactly are you verifying that the DLC port does not have power?

 

Cleric, I didn't see your last post yesterday while I was working on mine. Otherwise I would have added more info.


This is why I don't think fuse 34 is blown and also why I asked OP about their SES light (MIL). It's worth checking anyway.

 

Ahh yeah I was looking at mine with the 6MT and that's why it didn't show up.

 

here to revive this post because I am having the exact same problems as OP. So I did a non rev up swap on a 2006 g35 6mt(revup chassis). And now obd2 port is not working and my car is in some sort of seudo limp mode. Where it feels like it’s missing a lot of horsepower. And flashing check engine light(doesn’t sound like a misfire). Anyways. I need obd2 port to work to diagnose the engine problems. Anyways I’ve replaced both of the fuses you stated. Atleast I think I did(I suck at reading these diagrams so I might’ve replaced the wrong fuse that’s under the obd2 port. But anyways I’ve never used a multimeter but seems like it would be worth a shot for me to buy one. Anyone able to help me pin point what pins would mean what on the obd2 port?
Ps cleric like a year ago I made a post about my old car being stuck in limp mode after another engine swap I did a while ago and I think you’re the one who told me to check the three connectors next to the battery. Well. One of those connectors had a mf little pebble in it. Cleaned it out and instantly the car ran perfect again.

 

Any update on this post? Im having same issues but its only when i swapped to the engine, my obd only has power when the key is turned. I’m trying to get key fobs programmed, but the key has to be off for the program it with their scanner. The fuses are good. I don’t get 12v at pin 16 without the key turned into accessories or on, im lost

 

so pin 16 is your battery pin meaning it should have constant power without the key in the ignition. You can clip the wire behind the plug and For pin 16 just run a wire from the battery to it (fused of course) aka jumper wire. I personally haven’t fixed my obd port yet but this is what I was told by someone else when I was first looking into my problems, I honestly haven’t even taken a multi meter to mine yet so I’ll have to see if I’m running into the same issues with power

 

So i some what figured it after looking at the full service manuals the obd port power wire goes into a super junction box labeled F102 and its a red wire the same as the power wire i had a water leak that got on top of that junction box and corroded that pin and broke off, then snipped that power from the top and bottom off were they would originally connect and bam the obd port works again like normal. The only thing is now i dont have any CAN communication when the ignition is off. I cant do any key programming because the car has to be turn off and on and CAN communication has to work. Ive dug all through the service manual and trace the CAN LINES to the obd port to the junction box F102 and to the ecm and makes continuity so it makes it, and now im at a lost now. Anyone ever had no communication when the car is off? I cant read codes or do anything with the obd port.