Engine miss and cannot communicate with ECU

SKED

MEMBER
2000 FORD EXCURSION
6.8L
V10
4WD
AUTOMATIC
107,000 MILES

Recently, and quite suddenly developed miss, dead miss. Engine service light not lit while running, but does light with key on prior to starting. Code reader lights up and it's other functions work, but I get "error communicating with ECU" message and it won't connect or read. I was, and still am thinking a bad plug or coil and was hoping the code reader would point out the problem cylinder. Any clue on what to look for with the ECU communication problem? Will disconnecting battery reset ECU to fix communication problem? (I assume it will likely erase error codes) Any help appreciated.

3 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning,

First, erasing codes does nothing. You need to leave it alone and need to find out why there is no communication. It could be your code reader. Try it on another car to be sure.

If you want to check the misfire manually, disconnect one coil at a time while the engine is running until the one that makes no change. That is the cylinder. I would replace all the plugs and coil boots anyway. The coils do not need to be replaced, just the rubber ends. You can get them at a parts store.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Roy

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Sunday, March 10th, 2019 AT 7:48 AM

SKED

MEMBER
2 POSTS

Thanks for the response. I have plugs but will also get the boots.
My code reader works on both a 2013 Hyundai and 2010 Dodge truck, but I haven't tested it on another Ford. I have a different reader ordered and hope that's the issue with not being able to communicate with the ECU.
To clarify, my purpose for disconnecting the battery wasn't to erase the codes. I only mentioned that as a side effect of disconnecting the battery.
My hope was that by disconnecting the battery it would reset the ECU and fix the communication problem with the reader. I would still like to get a code reading just to make sure there are no other issues such as EGR, MAF or other sensors.
Again, thanks for the advice.

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Sunday, March 10th, 2019 AT 12:23 PM

ASEMASTER6371

MECHANIC
52,797 POSTS

You are welcome.

Against what most people say, disconnecting the battery does not reset the ECM. All it does is make the ECM forget the code and does not change any other information. The codes that will or went away will reappear when the system fails the internal tests the ECM runs when it is running.

Roy

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Sunday, March 10th, 2019 AT 12:28 PM