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2005 Cadillac CTS
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33 Posts
Discussion Starter #1
Ok so the car has been misfiring for some time and pulled the codes off and it says injector circuit 2 open. So I replaced the injector. Started the car it ran fine for couple of miles and started misfiring again with same code. So I thought ok maybe fuel injector wiring hareness is bad so I replaced that it ran fine for 10 seconds then misfired with original code injector circuit 2 open no other codes just that injector. I'm at a loss on where to go from here. I've read from some other post that the next problem would be the ecu/ecm but the symptoms they were saying would be a tell sign for a bad ecm aren't present with my ecm so I have no suspicion that the ecm would be the problem but I could be wrong. If you have any advice it would be appreciated.
 

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I had an injector circuit 5 open code. A new ecm solved the problem. These cars are known for the ecm going bad. If you come to the conclusion to replace the ecm ,know that a new one is very expensive. I was able to get a refurbished one from Blue Streak electronics who are affiliated with Autozone. They frequently do not have a ready unit though. The other options will be one of the vendors that sale preprogrammed units. Good luck.
 

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2005 Cadillac CTS
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Discussion Starter #3
I had an injector circuit 5 open code. A new ecm solved the problem. These cars are known for the ecm going bad. If you come to the conclusion to replace the ecm ,know that a new one is very expensive. I was able to get a refurbished one from Blue Streak electronics who are affiliated with Autozone. They frequently do not have a ready unit though. The other options will be one of the vendors that sale preprogrammed units. Good luck.
Did the unit come preprogramed and how did you come to the conclusion of the ecm being bad?
 

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2005 Cadillac CTS
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Discussion Starter #4
I had an injector circuit 5 open code. A new ecm solved the problem. These cars are known for the ecm going bad. If you come to the conclusion to replace the ecm ,know that a new one is very expensive. I was able to get a refurbished one from Blue Streak electronics who are affiliated with Autozone. They frequently do not have a ready unit though. The other options will be one of the vendors that sale preprogrammed units. Good luck.
Could you also provide link to the one you bought there site doesn't have purchase option.
 

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2014 ELR
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191 Posts
Ok.
Long time GM development tech here..
Read this slowly and carefully.
The. ECM. Is. Not. The. Problem.
Keep that in mind.
I have worked on these cars since before they had ECMs.
In my 30+ years I have replaced exactly 0 bad ECMs and 1 bad BCM.

Here's the thing.
What do you have to do to replace the ECM?
Remove the connectors!
Where are you most likely to have a bad, corroded terminal that will show up as an open circuit?
In a connector!
What happens to a corroded connection if you unplug it and plug it back in?
It often times "fixes" itself.
There is also at least one other connector between the ECM and the injector. It might have a problem as well.
Inspect all the connections and follow the diagnostic procedure in the service manual.
And don't just look at the procedure, actually take the time to follow all the steps and do it correctly. That last part is important and why 90% of ECMs replaced at dealerships are found to be working just fine when they are returned after they are replaced.
Now, if you follow all the procedures and check all the wiring you may find out it is the ECM. They are not perfect and we are talking about a 15 year old piece of electronics. But you really need to start with the idea that..
The. ECM. Is. Not. The. Problem.
First off they rarely fail.
Second, its never a good idea to go into a troubleshooting process have already determined that the most expensive part is bad. Not good economics and not good troubleshooting period.
Ok, I'll get off of my soapbox now.
🙂
 

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2005 Cadillac CTS
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Discussion Starter #6
Ok.
Long time GM development tech here..
Read this slowly and carefully.
The. ECM. Is. Not. The. Problem.
Keep that in mind.
I have worked on these cars since before they had ECMs.
In my 30+ years I have replaced exactly 0 bad ECMs and 1 bad BCM.

Here's the thing.
What do you have to do to replace the ECM?
Remove the connectors!
Where are you most likely to have a bad, corroded terminal that will show up as an open circuit?
In a connector!
What happens to a corroded connection if you unplug it and plug it back in?
It often times "fixes" itself.
There is also at least one other connector between the ECM and the injector. It might have a problem as well.
Inspect all the connections and follow the diagnostic procedure in the service manual.
And don't just look at the procedure, actually take the time to follow all the steps and do it correctly. That last part is important and why 90% of ECMs replaced at dealerships are found to be working just fine when they are returned after they are replaced.
Now, if you follow all the procedures and check all the wiring you may find out it is the ECM. They are not perfect and we are talking about a 15 year old piece of electronics. But you really need to start with the idea that..
The. ECM. Is. Not. The. Problem.
First off they rarely fail.
Second, its never a good idea to go into a troubleshooting process have already determined that the most expensive part is bad. Not good economics and not good troubleshooting period.
Ok, I'll get off of my soapbox now.
🙂
I agree with what you said expensive first is bad as for testing connection I changed the wiring harness connected to the injector and injector where changed so the only thing I think that is between harness and ecm is a think wire harness with other wires also I unfortunately don't have troubleshooting manual so not sure how to trace the harness to the ecm and when you mention connector corrosion are you refering to the connector that connects to the ecm or injector.
 

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2014 ELR
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I agree with what you said expensive first is bad as for testing connection I changed the wiring harness connected to the injector and injector where changed so the only thing I think that is between harness and ecm is a think wire harness with other wires also I unfortunately don't have troubleshooting manual so not sure how to trace the harness to the ecm and when you mention connector corrosion are you refering to the connector that connects to the ecm or injector.
Yes, that is the first place I would look bu it could be in C120 or C121 as well.

584630
584631
584632
584633
584634
584635
 

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2014 ELR
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191 Posts
I agree with what you said expensive first is bad as for testing connection I changed the wiring harness connected to the injector and injector where changed so the only thing I think that is between harness and ecm is a think wire harness with other wires also I unfortunately don't have troubleshooting manual so not sure how to trace the harness to the ecm and when you mention connector corrosion are you refering to the connector that connects to the ecm or injector.
Notice on the diagnostic guide what it takes for the code to clear, 4 consecutive ignition cycles without a failure.
 

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2014 ELR
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191 Posts
Here a few other things you will need.
The ECM C1 connector (The black one)
584643

The overall schematic of the fuel injectors.
584644

C121 The Engine harness to the fuel injector harness, in the engine compartment, on top of the engine at the right front of the intake manifold
584645

C120 The Engine harness to the POA engine harness, in the engine compartment, on top of the engine at the front of the right valve cover
584646

Let me know if you need anything else.
 

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Kudos to a very good and detailed diagnostic procedure that was given to you. I agree that every thing should be ruled out in any job before going to the most expensive item. Having said that there are multiple post about the ecm going bad , go into the search feature to read some of the situations. I hope that you are not facing replacement, a new ecm is what fixed my problem. As I stated in my post Blue Streak often times will not have a replacement. You can pull up the Auto Zone online store site and put your car info in to see if they have a replacement. They did not have my ecm at first, I kept putting the info in on different days and got lucky when one showed , I quickly purchased it. Once again I hope replacement will be your last option if at all. Good luck.
 
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