: Coil Questions

01-08-07, 08:05 PM
I have a 99 sts with a bad miss. 140K miles. I'm getting a P0300 code. The SES light is blinking. I hooked up my Sunpro Engine Whatchamacallit to all of my plug wires. It appears that #2 and #5 are both firing sporadically. They are both on the same coil, so I am thinking the coil is the problem. So, my question is, can that coil be replaced seperately, or do I have to get the whole "pack" (all 4 of them)??

Thanks in advance.


01-08-07, 08:49 PM
You can replace it seperately. One small bolt on each side and lift it off. Swap it with a known good one from another car and see if that cures the problem. If so, buy a new one. You could also check them with a DVM. I think Clark just posted the proceedure and acceptable resistence readings in another post.

01-09-07, 10:09 AM
Using an ohmmeter, check the resistance between the primary terminals on the underside of the coil. The resistance should be 0.50-0.90 ohms.
Check the resistance between the secondary terminals. It should be 5000-10,000 ohms.
If the coil failed either test, replace the coil.

01-12-07, 12:52 AM
Thanks Clark. I pulled the suspect coil and put the ohmmeter on it. The primaries checked ok but I couldn't get any reading for the spark plug wire terminals. Put a new coil on it today and it seems to be running fine. The SES light is still on though, I wonder if it will go out on its own?

Hey I really appreciate folks like you who post on these sites. You guys have saved me alot of $$ and troubleshooting over the years.


01-12-07, 04:57 AM
Glad we could help.

01-14-07, 01:19 PM
Follow the instructions on the technical forum on how to read and reset codes. I got some use out of that. My car was also having spark issues randomly and it turned out to be 3 cracked(split open) coil packs, I just replaced them all.

01-18-07, 01:24 PM
Before you buy the parts, swap out your suspected coil etc. with another bank. Then clear all codes.

If you generate new codes on the cylinder(s) that got the suspected part, you know your hunch is correct and the part was in fact bad.

It's a cheap trick that I've used to confirm that injectors, wires, coils etc. are in fact the culprit before spending a dime.