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2G Diagnosing the diagnostic port

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dgdsm

10+ Year Contributor
173
4
Aug 24, 2008
Tarzana, California
I think there's something funny going on with my OBDII diagnostic port. About a week ago, my 10 year old code scanner stopped working. It looks like there's not enough power from the port to light the LED screen. But my bluetooth ELM327 adapter is working. I was thinking that the code scanner went bad, but today I took it to a smog test shop for a test and he said his machine couldn't read the RPMs through that port. My bluetooth adapter reads this just fine.

A YT video I found says that in some cars the OBDII port shares a circuit with the cigarette lighter, which has actually never worked in my car since I've owned it. I'm wondering why my BT ELM327 device would work but not a direct connection. I learned a bit about the OBDII commands that devices use to talk to the ECU and sent some simple commands a few times, but I don't see how that could have hurt anything.

Does the ECU have a low-power mode? Also, there's no VIN or other identification information in my ECU, so I don't know if it's actually the original one.

Any suggestions would be helpful.
 
The cig lighter has nothing to do with it. Check the "Door Lock" 10A fuse in inside fuse box which supplies power to the Data Link Connector port pin 16.

Is this the same for GST/GSX models? I've had issues with my scanner having issues "staying connected" to the port even though it's firmly attached. If I wiggle the port a little, it'll usually connect, but the last time it took a little more time. I figured maybe wiring is getting interfered or something.
 
Yes same for GST/GSX. Check the diagnostic port (aka data link connector) and your scanner connectors for pins that are dirty, corroded, bent, loose, not locked in place, etc. Push/wriggle each pin separately. Although possible, it's unlikely the factory wiring (unless someone made a mess of it of course). But if you suspect it, look behind the connector and wiggle each wire to check their connection, especially while the scanner is plugged in and on.
 
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This fuse is fine and the power door lock system is working.
The door ajar lamp isn't lighting though on the driver's side door, only on the passenger side door.
Maybe a bad ground or a drain somewhere?

There may be something going on with pins and connectors. The direct connection from the scantool cable seems a little sticky.

And it's clearly the port and not the 10-yo scanner. The scanner works and reads fine on another car.
 
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Well I reached behind the OBDII port and moved the wires around a bit and the 10-yo scantool works again (images attached). Could use some electrical contacts cleaner. The other (white) port is I guess the Mitsubishi MUT port ?
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When I got the Actron scanner back up, the ELM327/bluetooth scanner stopped working. I have now both the Actron and ELM327 scanners powering up and reading through the port.

I've pretty much confirmed at this point that it's the wire to OBD port pin #5 (Signal/ECU ground). I also sprayed some electronics cleaner thorugh pin #5. What I don't know is why moving and twisting that one wire makes a difference, or how one scanner device can connect and the other not.
 
I actually had an issue with obd2 devices staying physically connected. I popped out the ob2 port (just clipped into the bracket), and wrapped a couple layers of electrical tape around it. Trimmed up what ever was in the way of the pins. And everything is staying comnected.
Use to be i couldnt get 3 mins down the road with out my data logging cable losing connection. Even on a smooth road. 4 days later, havent lost connection at all.
 
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