cyl #3 coil is not getting a pulse. -UPDATE FIXED-

[Elkman]

I have a 2003 X5 3.0i After ruling out all other possibilities on the Cyl #3 misfire, I have concluded cyl #3 coil is not getting a pulse. I measured the resistance on all 3 wires from the DME connector to the coil connector and got minus point 2 (-.2) on all 3 wires. Would this indicate a bad DME or a bad wire harness?

[crystalworks]

You'd have to check for continuity to eliminate the harness. Not fun, but with some alligator clips and extra wire should be easy enough. Make sure to disconnect the battery as a precaution. It's good practice anytime unplugging an ecu, bcm, or lkm.

[oldskewel]

Originally Posted by Elkman

... I measured the resistance on all 3 wires from the DME connector to the coil connector and got minus point 2 (-.2) on all 3 wires. Would this indicate a bad DME or a bad wire harness?.[/COLOR]

If you're getting negative resistance, I will tell you, you are really on to something there. It could solve a lot of problems if you can scale that up.

[oldskewel]

OK, more seriously, there's something wrong with your test if you think you're getting negative resistance. With coils, even accurate resistance measurements may not tell the story.

Have you tried swapping two coils? Swapping two plugs? What makes you suspect #3 other than those measurements?

And for those Physics fans, negative resistance is not possible according to our present understanding of Physics. Last guy I met that even got zero resistance had a Nobel prize for the effort. Negative resistance would be an even bigger deal. But BTW, "they" probably thought zero was impossible too, before they found it was not.

[Elkman]

Have you tried swapping two coils? Swapping two plugs? What makes you suspect #3 other than those measurements?

Yes I have, it is not the coil, plugs or fuel injector or a vacuum leak. I have thoroughly tested all of that.
The -.2 resistance reading is about the same if I touch the 2 multimeter leads together. so the - reading might me the meter.


Thanks for your help

[cn90]

Or get an extra spark plug, attach to the coil, ground the coil, ask someone to crank the engine for 5 sec, you should see some spark.

If not, then either bad coil or bad wiring.

[kmm111]

Originally Posted by Elkman

I have a 2003 X5 3.0i After ruling out all other possibilities on the Cyl #3 misfire, I have concluded cyl #3 coil is not getting a pulse. I measured the resistance on all 3 wires from the DME connector to the coil connector and got minus point 2 (-.2) on all 3 wires. Would this indicate a bad DME or a bad wire harness?

Let’s back up. As this is your first post, how exactly did you “rule out all other possibilities”. The more information we have, the better we can help. As for your measurements. Was the DME unplugged? What kind of meter & leads did you use? Did you measure the lead resistance first & subtract it from your readings? What codes did &/or do you have?

[bcredliner]

I suggest reading for error codes before trying anything else.

[Elkman]

I used a grounded plug tester light as well as moving coils and plugs around, all coils were good. I tested the pulse to all the fuel injectors as well as the operation of all fuel injectors all were good. I did a smoke test to check for vacuum leaks. all was good. I check cylinder compression and fuel pressure. all were OK. I have concluded cyl #3 coil is not getting a pulse.

I need to check for continuity to eliminate the harness as suggested, I need to find out the best way to do that?


Thanks for the help Guys.

[Elkman]

Originally Posted by bcredliner

I suggest reading for error codes before trying anything else.

Misfire cyl #3 is the only code that comes up.
I do have 02 sensors that are acting up, Not active during live streaming, i think they were the post cat ones. but no o2 sensors codes come up.