OBD2 Strangness
Thread Starter
Newbie
Joined: Aug 2018
Posts: 2
Likes: 0
2007 ML320 CDI, 2012 Audi TT-S, 2003 Porsche Boxster
OBD2 Strangness
Hi All,
I'm new here but a regular on a few other car forums. For the most part, my 2007 ML320 CDI has been flawless and the few little questions I've had the search feature has solved everything for me perfectly! This one, I've tried google and searching every Mercedes and Jeep CRD forum I can find. Nothing yet! So here's my question to you guys: Up until a few weeks ago, I could put the key in the ignition position (engine off) and use my OBD2 scanner. Recently, I had an error that my device couldn't connect. That's odd. I turned on the engine and instantly I could connect. Turn off the engine, back into the ignition position and suddenly no connection again. Engine on, no issues.
What on earth could be causing this? I'm planning to do a tune on the car soon and there's no way I can tune with the engine running. Any thoughts would be greatly appreciated.
Thanks All,
RonJo
I'm new here but a regular on a few other car forums. For the most part, my 2007 ML320 CDI has been flawless and the few little questions I've had the search feature has solved everything for me perfectly! This one, I've tried google and searching every Mercedes and Jeep CRD forum I can find. Nothing yet! So here's my question to you guys: Up until a few weeks ago, I could put the key in the ignition position (engine off) and use my OBD2 scanner. Recently, I had an error that my device couldn't connect. That's odd. I turned on the engine and instantly I could connect. Turn off the engine, back into the ignition position and suddenly no connection again. Engine on, no issues.
What on earth could be causing this? I'm planning to do a tune on the car soon and there's no way I can tune with the engine running. Any thoughts would be greatly appreciated.
Thanks All,
RonJo
Member
Joined: Dec 2015
Posts: 110
Likes: 10
From: Northen California
2012 e350 bluetec
I can't explain why it worked with the key completely out. The OBD2 protocol calls for power to be supplied to the scanner. Usually you turn the ignition to the "accessory" position to connect so the scanner can begin identifying the specific protocol the vehicle is using and begin downloading information. If you start the car, it can then read "real time" data from the vehicle.
Without turning the key to a "power on" position (ie-position 2 or accessory) I can't understand how it ever connected unless your ignition is supplying power to something as soon as the key is inserted. Some vehicles supply power as soon as the key is inserted to power the anti-theft system. I know Porsche does that. Maybe you have a fuse blown or something.
Try turning the ignition to accessory mode without starting the engine and see what happens.
Without turning the key to a "power on" position (ie-position 2 or accessory) I can't understand how it ever connected unless your ignition is supplying power to something as soon as the key is inserted. Some vehicles supply power as soon as the key is inserted to power the anti-theft system. I know Porsche does that. Maybe you have a fuse blown or something.
Try turning the ignition to accessory mode without starting the engine and see what happens.
Thread Starter
Newbie
Joined: Aug 2018
Posts: 2
Likes: 0
2007 ML320 CDI, 2012 Audi TT-S, 2003 Porsche Boxster
I can't explain why it worked with the key completely out. The OBD2 protocol calls for power to be supplied to the scanner. Usually you turn the ignition to the "accessory" position to connect so the scanner can begin identifying the specific protocol the vehicle is using and begin downloading information. If you start the car, it can then read "real time" data from the vehicle.
Without turning the key to a "power on" position (ie-position 2 or accessory) I can't understand how it ever connected unless your ignition is supplying power to something as soon as the key is inserted. Some vehicles supply power as soon as the key is inserted to power the anti-theft system. I know Porsche does that. Maybe you have a fuse blown or something.
Try turning the ignition to accessory mode without starting the engine and see what happens.
Without turning the key to a "power on" position (ie-position 2 or accessory) I can't understand how it ever connected unless your ignition is supplying power to something as soon as the key is inserted. Some vehicles supply power as soon as the key is inserted to power the anti-theft system. I know Porsche does that. Maybe you have a fuse blown or something.
Try turning the ignition to accessory mode without starting the engine and see what happens.
I tried it in my Audi TT-S and it works in the accessory position and the engine on. I also tried it on the Volvo XC60 that I have access to and it works in both the accessory position and the engine running.
Member
Joined: Dec 2015
Posts: 110
Likes: 10
From: Northen California
2012 e350 bluetec
Check your battery to make sure you have 12V with the engine off. Some scan tools won't operate with much less than 12v at the connector port. Also, let the vehicle cycle through its start up and chime process before you plug in the scan tool.
The connector port can be checked for 12v by a knowledgeable person. If you have no voltage at the connector you may have a blown accessory fuse somewhere.
The connector port can be checked for 12v by a knowledgeable person. If you have no voltage at the connector you may have a blown accessory fuse somewhere.
Senior Member
Joined: Jan 2011
Posts: 422
Likes: 52
From: McDade, Texas
W211 e320 CDI
My Audi does this sometimes with the non KWP2000 series canbus languauge. If set to generic OBDII sometimes it connects to the first thing/language with a remotely correct “handshake”. Make sure specific language is set in scanner. I just bought a second icarsoft for Audi VW protocol to 100% eliminate issue there. Have correct VCDS cables and programs to ****** stock map and some definition files for editing. With the Benz I’ve had the same issue with several of the more generic code scanners, also with my Jeep CRD. Just a thought?
Member
Joined: Dec 2015
Posts: 110
Likes: 10
From: Northen California
2012 e350 bluetec
If you're comfortable using a multimeter you can test for 12v at the OBDii port. Pin #4 is a chassis ground and pin#16 is 12v positive.
The pins are numbered as follows:
Top row, left to right are pin #'s 1-8
Bottom row, left to right are pin #';s 9-16
You should see 12v when testing between ground pin #4 and the positive pin #16.
Caution: Make sure you test the correct pins and don't short anything in the process. Don't test if you're not comfortable.
Do a Google of the OBD port pin locations as a guide.
Note: Pin #5 is called a ground but it is used as a communication ground. Use the chassis ground, pin #4
The pins are numbered as follows:
Top row, left to right are pin #'s 1-8
Bottom row, left to right are pin #';s 9-16
You should see 12v when testing between ground pin #4 and the positive pin #16.
Caution: Make sure you test the correct pins and don't short anything in the process. Don't test if you're not comfortable.
Do a Google of the OBD port pin locations as a guide.
Note: Pin #5 is called a ground but it is used as a communication ground. Use the chassis ground, pin #4
