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George H.
George H., Hyundai Technician
Category: Hyundai
Satisfied Customers: 2075
Experience:  Hyundai Gold certified, ASE Master tech 15+ years
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Low voltage on pin 7 of DLC, K-Line unable to communicate

Customer Question

Low voltage on pin 7 of DLC, K-Line unable to communicate with scan tool and pass smog in CA
JA: What is the model/year of your Hyundai?
Customer: 2000 Elantra
JA: Are you fixing your Elantra yourself? What have you tried so far?
Customer: Checked voltage on all DLC Pins
JA: Anything else you want the mechanic to know before I connect you?
Customer: Vehicle has theft prevention key thing (immobilizer?) Might be preventing DLC communication
JA: Is the key stripped or worn?
Customer: No, but I have no problems with the key, just the OBD II scan tool
Submitted: 10 months ago.
Category: Hyundai
Expert:  Cary York replied 10 months ago.

Hi, I’m Cary and I’ll be helping you today.
Please understand that I can't smell, hear, or touch the vehicle, so patience is appreciated. Before leaving the site make sure and leave me a rating. You can still reply to me as many times as needed, even after the rating..

Have you checked fuses? I will look at a wiring diagram. Be right back.

Customer: replied 10 months ago.
Yeah, checked fuses. And I have some votlage on pin 7, 6.5-6.8v but it's supposed to be around 10-11v. I'd like to wire pin 7 straight to the ECU and bypass everything but I can't figure out what color wire to tap into
Expert:  Cary York replied 10 months ago.

Here are the 2 diagrams for the data connector.

Expert:  Cary York replied 10 months ago.

Do not see a wire going into pin 7. Let me look at the connector pinout.

Customer: replied 10 months ago.
Yeah I saw these and was confused too. I've got a black/blue white out of pin 7 and I'm assuming going somewhere before getting to the ECU
Customer: replied 10 months ago.
wire*
Expert:  Cary York replied 10 months ago.

I found this link. Still looking. Is the scanner you are using self powered or powered from the data connector?

http://pinoutsguide.com/CarElectronics/hyundai_obd_2_pinout.shtml

Customer: replied 10 months ago.
Powered from the data connector, but it fails at the smog stations too using any scanner, (tried 4 diff shops) Something is keeping the K-Line from communicating with the ECU
Expert:  Cary York replied 10 months ago.

Here is a diagram of the ECM and data connector wiring.

Expert:  Cary York replied 10 months ago.

When you plug the scanner up does it power up?

Customer: replied 10 months ago.
they all do. I've got 12 volts at pin 16 to power it.
Expert:  Cary York replied 10 months ago.

Good.

Expert:  Cary York replied 10 months ago.

Are you sure you are looking at the data connector correctly in order to identify pin 7? Here is a picture.

Customer: replied 10 months ago.
Yeah, positive. Mine has little numbers under it to tell you which pin is which, too.
Customer: replied 10 months ago.
But mine is black and blue coming out of pin 7
Expert:  Cary York replied 10 months ago.

I will opt out so another expert can help that has a better source of factory wiring diagrams.

Customer: replied 10 months ago.
Thank you, that's kind of you. I will give you a good review.
Expert:  david craig replied 10 months ago.

Hi Im David. first of all the voltage on k line should be 3.5vdc. that the first issue.

Customer: replied 10 months ago.
Oh, everywhere else I read said 10v on Pin 7.. I have 6.5 on pin 7 and 3.5 on pin 15.. What would cause that?
Customer: replied 10 months ago.
Also does Pin 2 do anything? I think that pin is empty on mine
Expert:  david craig replied 10 months ago.

sorry but i had to get some sleep last night.......... ill send you some info on the dlc

Expert:  david craig replied 10 months ago.

7 of the diagnostic connector with the ignition and radio turned ON. If it's under 9V, your K-line is fine. If it's over 9V, the results are inconclusive. pin 7(k line) interfaces with the abs,tcm,sas modules. with key off voltage must 3.5. if any different then the interfacing modules should be disconnected one at a time until the deisired voltage is obtained. this way you will be able to tell what module is causing the problem. note, that these results depend on the protocol that is being used on a particular vehicle make. variances in readings and pin outs depend on the protocol.

Customer: replied 10 months ago.
I have 6.5v at the K-Line with the key on engine off. I have 0 volts anywhere but pin 16 when the key is off. Are you saying Pin 7 with key off is supposed to have 3.5v? Please confirm.
My readings are with Key ON: 6.5v pin 7, 3.9v pin 15, 12v Pin 16, with pins 4 and 5 being a ground. I do notice a high reading on pin 1 when I switch to measure Ohms, but I don't think 1 is even used.
The problem is when we go to smog it anywhere here in California, they're saying they cannot communicate with the Computer which is a requirement here, and I can't communicate with any scan tool either.
Expert:  david craig replied 10 months ago.

with key off pin7 should read 3.5 with key on it should read somewhere around 7 volts. Do this, turn the key to the on position ...does the check engine light come on?

Customer: replied 10 months ago.
Yeah I've got nothing with key off but I figured that was normal since no data transfer with the key off. With key in on position I do have a check engine light on.
Expert:  david craig replied 10 months ago.

its definitely a problem with no voltage with the key off on pin 7.

Expert:  david craig replied 10 months ago.

you need to start disconnecting things the are on the k line. ie abs module, steering angle sensor and transmission control module. something is holding the voltage down

Expert:  david craig replied 10 months ago.

just checking in to see how its going