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ECM replacement?

Tiny
JOE WRIGHT2
  • MEMBER
  • 2010 CADILLAC CTS
  • 3.6L
  • V6
  • 2WD
  • AUTOMATIC
  • 175,000 MILES
I can’t find the ECM, it is not next to the fuse box, under the hood. Your diagram, says that the v-6 is on the left rear engine compartment, but I still don’t see it. I’m not an idiot, I just can’t find the darn thing. Is it under the air box?
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Wednesday, March 17th, 2021 AT 9:16 AM

90 Replies

Tiny
AL514
  • MECHANIC
  • 4,108 POSTS
Hello, this is 2010 Cadillac cts sedan 2wd, 3.6liter engine. The ECM is located in the left front of the engine compartment. This diagram should help. Sorry for the 3 diagrams, I'm having trouble erasing 2 of them. But they're all the same.
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Wednesday, March 17th, 2021 AT 11:42 AM
Tiny
JOE WRIGHT2
  • MEMBER
  • 80 POSTS
So what does this say that you sent a few days ago, because the ECM is not next to the fuse box. As I have stated several times before. I highlighted the statement from your email.
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Wednesday, March 17th, 2021 AT 12:05 PM
Tiny
JOE WRIGHT2
  • MEMBER
  • 80 POSTS
Is not left front, the drivers side?
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Wednesday, March 17th, 2021 AT 12:07 PM
Tiny
AL514
  • MECHANIC
  • 4,108 POSTS
If you look at the lower picture, notice the arrow, that's pointing forward on the vehicle. So if you're looking at the engine compartment it will be on your left side (passenger side). It's probably under the fuse block. I understand your frustration, we go through the same thing trying to find modules some times. Try following the wire harness, that might help as well. Is there something wrong with the ECM?
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Wednesday, March 17th, 2021 AT 1:00 PM
Tiny
JOE WRIGHT2
  • MEMBER
  • 80 POSTS
Read my previous question as far as what’s wrong, maybe you have a different opinion.
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Wednesday, March 17th, 2021 AT 1:18 PM
Tiny
AL514
  • MECHANIC
  • 4,108 POSTS
Here is a picture of the ECM:
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Wednesday, March 17th, 2021 AT 1:19 PM
Tiny
AL514
  • MECHANIC
  • 4,108 POSTS
I don't have any previous questions from you. Did you chat with a different Technician?
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+1
Wednesday, March 17th, 2021 AT 1:21 PM
Tiny
JOE WRIGHT2
  • MEMBER
  • 80 POSTS
Yes, my A/C is intermittent, not the relay, but intermittent ground from the ECM.
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Wednesday, March 17th, 2021 AT 1:25 PM
Tiny
AL514
  • MECHANIC
  • 4,108 POSTS
So is it the compressor that stops running intermittently? You've checked that compressor is actually losing power at the plug on the compressor itself? Do you have auto A/C? Where you can change temperatures on either side differently?
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Wednesday, March 17th, 2021 AT 1:28 PM
Tiny
JOE WRIGHT2
  • MEMBER
  • 80 POSTS
https://www.2carpros.com/questions/ac-intermittent-5421860
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Wednesday, March 17th, 2021 AT 1:28 PM
Tiny
JOE WRIGHT2
  • MEMBER
  • 80 POSTS
The terminal at the relay has no ground. Pos to 86 reads 10.40 volts, then after driving the A/C works or sometimes doesn’t, did you get the link?
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Wednesday, March 17th, 2021 AT 1:31 PM
Tiny
JOE WRIGHT2
  • MEMBER
  • 80 POSTS
Yes, I have auto A/C, that’s not the problem.
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Wednesday, March 17th, 2021 AT 1:32 PM
Tiny
JOE WRIGHT2
  • MEMBER
  • 80 POSTS
86 to ground is 3.30 volts, and 10.40 vdc to positive.
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Wednesday, March 17th, 2021 AT 1:33 PM
Tiny
JOE WRIGHT2
  • MEMBER
  • 80 POSTS
The compressor and associated parts are okay, the relay coil just doesn’t get a signal, every time from the ECM. Usually once the A/C works, it’s good for the day, but the next day it won’t work again.
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Wednesday, March 17th, 2021 AT 1:35 PM
Tiny
AL514
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Okay, I see what's going on, you're saying that pin 86 isn't going to ground. That's the pin the ECM grounds to engage the A/C relay. I'm just catching up on what's going on. So you are reading 3v on pin 86?
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Wednesday, March 17th, 2021 AT 1:37 PM
Tiny
JOE WRIGHT2
  • MEMBER
  • 80 POSTS
3 vdc to ground.
10.40 vdc to positive terminal.
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Wednesday, March 17th, 2021 AT 1:40 PM
Tiny
AL514
  • MECHANIC
  • 4,108 POSTS
If you're reading 3v and using the battery as ground, then you're reading voltage drop on that circuit. I see pin 44 dark green/white wire is the ECM pin for the relay. So I'm assuming you're trying to check that pin at the ECM. You're getting only 10volts at pin 85?
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Wednesday, March 17th, 2021 AT 1:41 PM
Tiny
JOE WRIGHT2
  • MEMBER
  • 80 POSTS
Yesterday I drove 100 miles nonstop, no A/C. Got out, engine off. 10 minutes later started car and A/C worked the rest of the day, starting and stopping car several times throughout.
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Wednesday, March 17th, 2021 AT 1:44 PM
Tiny
AL514
  • MECHANIC
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From my experience, I'd take a look to the under side of that fuse block in the engine compartment. I bet there's some corroded wires underneath the fuse block. I've seen that many times. Any green corrosion is going to be an issue.
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Wednesday, March 17th, 2021 AT 1:46 PM
Tiny
JOE WRIGHT2
  • MEMBER
  • 80 POSTS
Lol, I would check it at the ECM, if I could find it. No, I get 14 vdc at 85, but no ground on 86.
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Wednesday, March 17th, 2021 AT 1:46 PM

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