Computer or Electrical Issue

None of these wires add up. There's way more wires at the ECM than shown. And they aren't numbered either, I'm getting confused.

Correct. This wiring diagram is only going to show wires that are part of this system.

So hopefully this connector view of the ECM will help with this.

These wires are on EM83 connector. Then they are numbers 15, 24, 16, 25.

On wires 15 and 24 on the EM83 connector I get 1volt. Unplugging modules didn't change this except unplugging the instrument cluster, which brought it down to 0.2 volts. On wires 16 and 25 I can't get any voltage. But I'm not sure if there is some operator error here. Also the transmission computer has some corrosion. But nowhere near the level as that of the dlc connector. I attached photos.

Okay. First any corrosion on these pins will cause shorts so that needs to be addressed. Was this vehicle in a flood? This is a lot of corrosion. If it was then we are going to have all sorts of connectors that look just like this.

As for the voltage readings. Those are not close to being correct. However, I just want to make sure you are checking these correctly. Are you checking the voltage from pin 15 to 24 and then 16 to 25? Or are you checking the voltage on pin 15 and the other lead on ground? Then 24 and ground, 16 and ground, 25 and ground?

I have to stick a small wire into the connectors so I get get my leads on it. Have one lead on 16 (-) and one lead on 25 (+) and same for the others.

Okay. Sorry for the confusion. We need to check each of those wires to ground. So do the exact same thing except but the black lead of your meter on a good ground and leave it there, and then switch the red lead between each of those 4 wires.

Okay, so I have new information then. For my ground I used the strut tower nut/stud next to the ECM.

These are all voltages at the EM83 connector with the key ON.

EM83 connector, everything plugged in normally:
#16: 2.05V
#25: 3.04V
#15: 1.68V
#24: 3.28V

EM83 connector, Instrument cluster unplugged:
#16: 2.58V
#25: 2.35V
#15: 1.68V
#24: 3.29V

EM83 connector, transmission module unplugged:
#16: 2.06V
#25: 3.13V
#15: 0V
#24: 0V

Okay. Let me try and breakdown what is happening. It will help if you look at the wiring diagram of this network while reading through this.

This CAN network is what we call daisy chain network. That means starting at the DLC the wires run to the cluster. Then from there they go to the gear selector, then the adaptive speed control and so on down the line.

So with everything connected, you have incorrect voltage on the entire network. You checked this at the ECM so before the ECM (modules above the ECM on the diagram) your voltages were close but not correct. This would indicate an issue in one of these modules or wiring.

However, when you unplug the cluster, which is at the end of this part of the chain, your voltage on these pins (16 and 25) return to perfectly normal.

However, the modules that are part of the chain below the ECM still have incorrect voltage. This means you still have an issue there. Removing the TCM breaks the chain and causes this to have no voltage on that portion.

This is very odd behavior. So I think I am getting more convinced that this was a flood vehicle and you are going to find corrosion in a lot of connectors.

In other words, I don't think you are going to find one thing, replace it and fix all these issues.

You already found a lot of corrosion on the DLC which I have not seen on vehicles that were not submerged in water but you now have multiple places that have considerable amounts of corrosion.

At this point, I would suggest starting with inspecting connectors related to all these modules and any corrosion you find, fix it by replacing connectors or modules and then retest the system. If it is not fixed, check the voltage again to see if is closer to the 2.3 and 2.7 as I suspect the more you find and fix it will slowly change that voltage.

If unhooking the cluster gets that portion of the voltage to return to normal the we have an issue with the cluster as well.

The only thing I haven't checked is the adaptive speed control module and the module on the top that says "programming" for the trans. I can't find these. But I've only seen corrosion at the TCM and at the harness for the transmission range sensor, so far. So at least we know the cluster has an issue.

So I decided to plug everything back in and test the TCM connector. Here's what I found:

#82: 2.48V
#83: 2.48V
#85: 2.38V
#86: 2.62V

You said the voltage should be the same throughout the system. So if the voltage looks correct here and wrong when it's connected to the TCM, is the TCM an issue? And being later in the chain than the cluster, possibly both the cluster and the TCM have an issue?

Sorry. Maybe I misunderstood. If this was the voltage with everything hooked up except for the TCM then you are correct that the TCM appears to be the issue.

Great job doing that. We would have gone down the wrong path if you would not have done that.

Yes that's the voltage with everything hooked up, except the TCM. That is the voltage at the TCM connector. So then, would that mean both the instrument cluster and TCM are bad?

It does not mean that the cluster is faulty as well. If everything is hooked up and you have correct voltage then what is unhooked is all that is wrong.

The only thing that gives me pause is that when your two voltages are exactly the same it points to the fact that the wires are shorted together.

So try unplugging the cluster as well as the TCM and see if the two voltages that are 2.48 split a little more and that will point to a cluster issue.

If not, I would go with the TCM or a wiring issue with the TCM connector but this acts like a module.

I went to double check the TCM connector. Maybe I did something wrong previously. Here are the values right now:

#86: 2.61V
#85: 2.38V
#83: 3.11V
#82: 1.90V

Okay. Just to confirm, you have everything except the TCM plugged in and these are your voltage?

If that is the case, your TCM is an issue. What is not clear on this vehicle is if the 3.11 and 1.90 volts is close enough for it to communicated.

What I would do at this point, is replace the TCM and then plug everything back in and see if you get the P1642 code to return. I suspect all that will be repaired which will fix the majority of these issues if not all of them.

My assumption is that the 3.11 and 1.90 will be corrected once the system is all connected with a functional module.

That is possible. However, the way this system works is these modules send coded messages across these two wires. The way that it has to do this is by having this voltage spread by the half voltage.

So if the spread is too much or two little the message comes in corrupted so that module doesn't know what it was.

So this amount could be just fine but I agree, we know that TCM is an issue so we need to start with that.

Let us know what happens. Thanks

Sorry for the delay. Had to wait for the part and do some other unrelated repairs. The 17 codes so far have gone away. And the car does drive now and no failsafe engine mode. So far so good. I'm patting myself on the back on this one.

Pat yourself on the back again because you deserve it. Thanks for the update and sticking with us to let us know what happens.

Thanks again for using 2CarPros.