ECM replacement ?

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.

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.

Is not left front, the drivers side?

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?

Read my previous question as far as what’s wrong, maybe you have a different opinion.

Here is a picture of the ECM:

I don't have any previous questions from you. Did you chat with a different Technician?

Yes, my A/C is intermittent, not the relay, but intermittent ground from the ECM.

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?

https://www.2carpros.com/questions/ac-intermittent-5421860

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?

Yes, I have auto A/C, that’s not the problem.

86 to ground is 3.30 volts, and 10.40 vdc to positive.

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.

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?

3 vdc to ground.
10.40 vdc to positive terminal.

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?

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.

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.

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.

Check that EMIS 2 15amp fuse as well. Make sure it looks okay, has no signs of heat which would indicate resistance in that area. That fuse feeds the fan relays as well.

That's not good because I’m red/green colorblind, lol. but I do know enough (40 years HVAC ) not cars though, (different animal) The car is old but in excellent condition, like new...

I’ll pull the fuse box, and check it out.. maybe at least I’ll find the ECM. thanks for your input.
By the way, my relay terminals are different than your schematic, 37 goes to clutch coil, 87 is hot all the time.. I know it’s irrelevant but I just wanted you to know. I realize you can’t put the relay in wrong by design..

I only have one fan on the condenser.

https://www.2carpros.com/images/question_images/377149/large.jpg

I don’t think emis2 is a problem, because the voltage there is good, while the other side of relay is not a constant ground when A/C is on.

I’ll check it out as you say though. thanks

Then yes on pin 86, if you're reading 3v, that's voltage drop on the ground circuit to the ECM, or one of the ECM grounds is corroded. The ECM grounds are going to the top right of the engine block. But if you can follow the dark green/white wire from the fuse block and see if you find any contact points where it might have rubbed threw and got corroded inside. But that ECM is in the left front of the engine compartment. Probably under the fuse block. It's got 2 bulk connectors going to it.

Left front facing the car?

That's odd about the pins being backwards. I'm going to check if it's different on another model. But these diagrams are from All Data. It says pin 30 comes from A/C clutch fuse and 87 goes to compressor.

Yes, facing the engine, left front is ECM.

Help. I’ve loosened the two screws and 5 plastic tabs, but the rear of the fuse box won’t release.

Here's the instructions for pulling the top off. They can be tricky.

If you can pull the box up enough just to see underneath, maybe try a mirror. You just need to inspect the connections. Check any engine and body grounds as well. They need to be clean and tight. Here's a technical service bulletin that might help.

My box has 5 tabs, when i pull up.. the rear of the box is saying no.
Also the connection underneath wants to come with the box, is that normal? The rear connection is staying down, loose from the box.

Can you just unbolt the whole box? all you need is look underneath. You don't really need to pull the whole box apart. You should be able to see underneath by unbolting it from the body. In the picture also, there's your ECM.

Does this vehicle have a battery in the back as well?

Yes, battery in back. I got the box out, back hidden tabs total of 7 fyi.

I like the service bulletin.

There's a bulk connector in back near the battery too. It's behind the trunk inside panel incase you need to check back there too. And yes that's a good service bulletin for this issue.