Codes P0302 and P0306, test for bad wire to coil pack from PCM?

Tiny
MIKE GALLEGO
  • MEMBER
  • 2001 FORD TAURUS
  • 3.0L
  • V6
  • 2WD
  • AUTOMATIC
  • 153,000 MILES
I'm getting misfires on cylinders 2 and 6 which share the same coil. P0302 and P0306. Rough idle has gotten progressively worse over the last 3 weeks. Changed plugs, then plug wires, then coil pack. Still getting the same codes and engine is getting worse. I get weak spark with probe from cylinders 2 and 6, on both the previous coil pack as well as the new coil pack. I read to test the wires running from the coil pack to the pcm. If the wires are good, then I may have a bad PCM. I have no experience with electrical or using multimeters.

How do I test the 3 wires? I know the pin locations on the PCM connector, I just don't know how to test the wire. I assume with a multimeter, but do I disconnect the wires from both sides? Am I connecting the multimeter to both ends of the wires (one by one) simultaneously to form a loop? Please explain as if I'm a 4 year old.
Friday, August 18th, 2023 AT 11:13 AM

5 Replies

Tiny
AL514
  • MECHANIC
  • 4,632 POSTS
Hello, you can do a resistance check for each wire from the ignition coil pack to the PCM. I'll post the wiring diagrams, but yes you have the right idea, For the yellow/red wire at the coil will be the same color at the PCM, check from end to end, I'll post more info in a minute.
For Ignition coil B the yellow/red wire goes to PCM pin 52 it will be the same color at the PCM connector. With the PCM connector and Ignition coil pack unplugged, set the multimeter on Ohms setting and check the resistance from the coil end to the PCM end. If the resistance is below 5 ohms, check the wire at the Ignition coil to any ground location to make sure the wire is not shorted to ground anywhere. There should be no reading. Hopefully, that makes sense. After you check the wire to the PCM, let us know what you find. If there is a short to ground on that wire, you'll have to find that.
But start with just checking that wire for the coil in question. If you have any questions just ask.
Before replacing at PCM there are some other things to check.
The yellow/white wire is the wire for cylinders 2 and 6.
Be sure you have the Key Off when unplugging components.

https://www.2carpros.com/articles/how-to-use-a-voltmeter
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Friday, August 18th, 2023 AT 11:46 AM
Tiny
MIKE GALLEGO
  • MEMBER
  • 3 POSTS
Frustrated. I used paper clips to assure a good connection and tested all 3 wires. The multimeter just stays at one. Doesn't move. If I test my pliers it fluctuates from zero to 4 and when I test a simple wire in my toolbox it gives me zero. I don't have clips, just probes.
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Friday, August 18th, 2023 AT 1:48 PM
Tiny
AL514
  • MECHANIC
  • 4,632 POSTS
Try just touching your multimeter leads together, then wiggle the leads around while still touching and make sure you dent have any broken wires in the multimeter leads. Are you using a digital meter or old analog meter? And are you on the correct setting? Take a picture and post it here. It is always important to test meter leads before checking circuits.
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Friday, August 18th, 2023 AT 2:33 PM
Tiny
MIKE GALLEGO
  • MEMBER
  • 3 POSTS
It seems to work okay. Just can’t get a connection. Is there a trick?
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Friday, August 18th, 2023 AT 2:51 PM
Tiny
AL514
  • MECHANIC
  • 4,632 POSTS
Well, I don't think a paperclip is going to conduct very well. Are you having trouble making a connection inside the PCM connector? One thing you need to be careful of is spreading any of the female type connectors, if you try getting a connection by pushing the meter leads into a female connector it will never make good contact again with the original flat male pin on the PCM or whatever that connector plugs into.
If I don't happen to have the proper back probing pin with me, I'll use one of these T pin types, they are small enough not to spread any connectors, but also conduct enough to get a good reading.
Getting a good connection is always difficult with ECM/PCM connectors because some can be very tiny. They are not designed to be unplugged multiple times. Sometimes I will even just back probe a connector that's unplugged to avoid spreading any pins and ending up with pin fitment issues, they cause more problems than you would believe.
The 2nd diagram is an example I made up of back probing a sensor connector. Notice using the T pin on the back side of the connector where the wires enter. As long as there isn't a really tight weather pack seal on it.
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Friday, August 18th, 2023 AT 3:22 PM

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