obd2 wiring question

[EvanD]

I am trying to match these wires up to an aftermarket gauge.


How do I tell which wire goes to what pin on other end of the plug??? Without a little disassembly???

 

[Donald]

What do the directions on the gauge say? Or directions that came with that plug. I do not think all the wires are used. Maybe 4 or 6.

 

[clinebarger]

Ohm them out with a DVOM.

 

[Trav]

http://pinoutguide.com/CarElectronics/car_obd2_pinout.shtml

 

[Chris142]

Originally Posted By: clinebarger
Ohm them out with a DVOM.
x2. Harbor freight gives them away! They are fine for this kind of work.

 

[EvanD]

Originally Posted By: Chris142
Originally Posted By: clinebarger
Ohm them out with a DVOM.
x2. Harbor freight gives them away! They are fine for this kind of work.



duh. I never thought of that. Thank you

 

[i_hate_autofraud]

Caution !!

A DVOM is good for finding ground and +12V. But other wires are data lines from the car's computers. If you use a DVOM in Ohms mode, you're applying voltage to OBDII connector pins that may not tolerate it and blow back into the computers. Figure $$$$$$

Use DVOM in DC Volts mode only and check for +12V. Data pins will read like 0V but are not the same as ground. Get more info from the maker of the gauge. Don't guess!

Good luck!

 

[Johnny2Bad]

The phrase Digital Volt-Ohm Meter (DVOM) doesn't really refer to anything. The two types of meters are Volt-Ohm Meter (VOM) and Digital MultiMeter (DMM). It is a mistake to use the phrase DVOM as it refers to both types, and therein lies a danger.

The reason you don't want to refer to a DVOM is because a VOM, which is an analog device with a meter movement, will definitely kill your car's digital management computer(s). Never use one on a modern automobile.

A DMM (where the readout is via the familiar multiple 7+ segment number display) is OK to use on your car and with automotive computers. The proper procedure is to disconnect the negative terminal of the battery and wait a certain amount of time ... hard to say if it's 10 minutes or 30, but if you sit down and drink a beer before picking up the meter, you are probably good to go.

And the way these devices are manufactured, the required chipset is inexpensive; the $10 DMM is a perfectly capable device used within it's voltage and current limits.

I have a number of DMMs ... one benchtop model costs $4500. I have a good portable handheld (FLUKE 87-V), two or three middling handheld DMMs (about $50 each) and a couple of dirt cheap units. Sometimes I use four or five at the same time, if I'm measuring a project I'm building. I used my 87-V just this afternoon, fixing my fancy electronically controlled stove. Saved me $200 in parts and who knows what for a service call.

 

[Vikas]

What exactly are you trying to do with the OBD-2 wires? Remember that it uses different protocols and thus different wires depending upon the manufacturer and the age of the vehicle.

I think you have misunderstood the gauge if you think it is asking you to hack in to OBD-2 wiring. The only thing it might ask you to do is to get the constant 12V power source from the OBD connector.

 

[HerrStig]

I'd use an 11 megaohm meter or an O'Scope and avoid using the ohms scale or continuity tester to avoid putting the internal meter voltage on something fragile. This is not a place for a DYI to be using an inexpensive meter unless he/she has some electronics training. Measure all the voltages present on the the wires connected to the plug with the high impedance meter first to avoid creating a low ohms path to ground for a lead to an input or device which won't tolerate that condition.

 

[Vikas]

I would advise to just NOT do anything on that OBD-2 connector unless you really know what you are doing. Your asking this question means you don't know what you are doing.

 

[zzyzzx]

Originally Posted By: Vikas
I would advise to just NOT do anything on that OBD-2 connector unless you really know what you are doing. Your asking this question means you don't know what you are doing.


I agree. I want more information on the aftermarket gauge.

 

[Vikas]

I love it when everybody else tells him to buy $350 fluke dvmm so that he can destroy his car's computer correctly

 

[nthach]

My advice - unless you're connecting a scan gauge or anything that is a datalogger or OBD-II code reader/dongle - don't. There might be interfaces that can extrapolate the data over the OBD-II databuses and convert them to analog signals for gauges. If you're trying to install a remote start, you will need a interface for both the immobilizer and tach signal.

 

[SHOZ]

There are no analog signals coming out of the ODBII connector except for battery voltage. All the scan gauges look to the CAN bus and get their info in digital form. There are no single separate signals for gauges.

 

[clinebarger]

You guys need to work on your reading comprehension skills, His question was......."How do I tell which wire goes to what pin on other end of the plug??? Without a little disassembly???" He said NOTHING about probing the OBD port!

 

[Vikas]

The person who can not answer that question on his own has absolutely no reason ever to hook up that contraption to car. If you can not think of a way to find which wire goes from one end to the other, you have no business even touching that thing.

 

[JetStar]

I'm really curious what this aftermarket gauge is.

 

[eljefino]

You guys are overthinking this!

Don't touch the car with the DVOM!

Just touch the pins on the dongle presented to us in the pictures, as well as the other end the wiring, to establish continuity on the foot of cable in the picture.

You can find OBDII pin numbers on google images.

It depends on if you use VPW, CAN, or a couple other protocols, which pin exactly you want.

I assume this is for a scangauge or what have you.

I don't see why said gauge doesn't come with appropriate wiring, though.

Don't plug your finished product into your car unless you're confident you did it right, though.