Hello

I found some old Threads about testing the Ignition coils with an ohm meter but could not find out exactly how to use the test Meter with the coils. I've been getting the PO300 code for a while and got the PO302 for one day, so I want to test the coils to get a better idea before I go out and spend money. Here are some pictures I found that might give you a better idea visually of what I mean.

I can't figure out where to connect the +/- probe on the coil.. I'm not very savvy when it comes to electrical meters. Can someone point me in the right direction?

Cheers,

 

So, I just had a coil go out on me in the past month or so. Luckily it thew a code and I know I needed a tuneup anyway, so I just replaced the coil on the dead cylinder and did all the plugs and the miss went away.

But for the sake of argument, I went and grabbed the dead coil from my garage and tested it.

This is the image from the thread where you got the other photo's:



First off, the multi-meter should be on 20kΩ so it shows you your figure in (x.xx) format. Ω is Ohm's, and it means you'll be checking resistance within a circuit.

http://en.wikipedia.org/wiki/Ohm

(example: '+1,-2' = Red test lead on first prong, Black on 2nd)

Now...

I don't think this test will ever be definitive since the 'Bad' Coil at the top left of the image (which I guess happens to be coil 2 since it isn't tested in the examples below it) seems to be giving a fairly close resistance reading on all counts except for being a smidge higher.

HOWEVER:

Upon testing my dead coil these were the results I got:

+1,-2: 1.54
+1,-3: i
-1,+2: 1.53
-1,+3: i
-2,+3: i
+2,-3: i

So basically, this tells me that if you get an infinite reading for one or more tests, where as every other good working coil gives you a reading (ie. the +1,-3 and +2,-3 tests) You probably have a problem somewhere.

While I can't tell you why or what the problem entails exactly, your figures should be somewhat similar to every other coil, if you run across a combination that doesn't give you a result (like a blank screen) it is probably your culprit.

Hope that helped clarify.

 

very nice, so what do you do with the 3rd prong or "pin" on the coil when testing, nothing?

 

If you're doing (+1,-2) than yes, you just leave #3 alone.
If you're doing (+1,-3) than the black test lead will be testing 3, and #2 pin will be left alone.

 

nice, thank you

 

Been awhile since I took a class in electronics but I thought when measuring resistance the polarity doesn't matter. (-1,+2) should be the same as (+1,-2). This looks like the case above but in the chart why would (-2,+3) be different than (+2,-3)? On second thought I guess there could be a difference if there were a diode in the system.

 

 

I just tested the 3 front coils.. I tested them at 200kΩ because 20kΩ would not show any results. These were the results:

Cylinder #2 Coil : -1,+2 = 190.0
Cylinder #4 Coil : -1,+2 = 191.8
Cylinder #6 Coil : -1,+2 = 188.5

Does this mean Coil # 6 is going bad and that could possibly be part of my Random multiple misfire code PO300?

Also can the coils can be tested while they are completely out or does it have to be pluged into the spark plug for accurate reading?