New to P5 Auto Tranny

It is the same ECU. It's only the wiring harness and instrument cluster that are auto specific.



I didn't know the cluster was automatic specific.


, and then wire the clutch pedal switch directly to the starter switch.


Don't forget, there are two clutch switches.




All I have left to do is try and make some resistor packets to match the resistances of the solenoids to get the CEL to go off.


Do you think that a cluster from a manual would avoid the resistor trick ?


I can post a complete re-wiring guide here if you all think that would be beneficial to anyone.



I would certainly be interested.

Maybe talk to Antoine and he can put it in the how-to section?

(there's still a few of us holding on to our old cars.)
 
"I didn't know the cluster was automatic specific."

Yes, it has the LCD on the left that shows the gear you are in. This is also a 2003 with the shifter mode transmission.



"Don't forget, there are two clutch switches."



Yeah, I meant to say the two wires. I think the second switch is tied to the same circuit as the neutral switch? It should be the same as far as I know.



"Do you think that a cluster from a manual would avoid the resistor trick ?"

Yes, it probably would, but the odometer is cluster specific and there is a 130k like discrepancy between the two I have.




"I would certainly be interested.

Maybe talk to Antoine and he can put it in the how-to section?

(there's still a few of us holding on to our old cars.)"

I'll write something up and PM him.
 
Yeah, I meant to say the two wires. I think the second switch is tied to the same circuit as the neutral switch? It should be the same as far as I know.



I think they might be separate?

The starter interlock is more of a power wire, while the other might be more of a signal wire?

There are two separate switches.
It might be for a reason?
 
I think they might be separate?

The starter interlock is more of a power wire, while the other might be more of a signal wire?

There are two separate switches.
It might be for a reason?


I'll certainly investigate more before posting anything. I think you're right.
 
I think they might be separate?

The starter interlock is more of a power wire, while the other might be more of a signal wire?

There are two separate switches.
It might be for a reason?

There are three switches in manual trans boxes; Clutch-starter interlock, Neutral switch -tells the ECM that car is in neutral and adjusts engine operation accordingly- and IF it has cruise control, a CC disconnect switch. All three are separate circuits.
 
There are three switches in manual trans boxes;...

I meant that there is two separate switches on the clutch pedal itself.

One is the starter interlock and the other runs to ECU as well as the CC module.

There is also a reverse switch in the transmission but I'm pretty sure that just turns the reverse lights on and off.
 
I meant that there is two separate switches on the clutch pedal itself.

One is the starter interlock and the other runs to ECU as well as the CC module.

There is also a reverse switch in the transmission but I'm pretty sure that just turns the reverse lights on and off.


I had wired the "Neutral switch" incorrectly at first and it caused some issues, so I cut the wires. Now I can't seem to detect any difference in the car's drive-ability with the wires to the neutral switch cut. I need to test it out with CC before I ignore it. It may be 100% CC related.
 
You're probably gonna pop a code.











And it's probably not a good idea anyway.

The ECU needs to know if you're engaged and in gear.



When you push the clutch, the ECU needs to know to go to idle.
 
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You're probably gonna pop a code.











And it's probably not a good idea anyway.

The ECU needs to know if you're engaged and in gear.



When you push the clutch, the ECU needs to know to go to idle.

Yeah, I plan to fully wire it correctly. I was just giving some information about what I noticed.

Before I get it inspected (apparently there is a 30-day wait due to COVID-19 for some reason) I plan to correctly wire the neutral switch and then install some resistors to turn off the CEL for the auto solenoids.
 
I have a manual trans gauge cluster if you're interested in it....Not sure what mileage is on it...bought it as a spare or project or something because I have sportronic. I have no use for it.
 
On a 20-year-old car, the mileage is almost irrelevant.

If it lived to be twenty, it must have been properly maintained.

Our cars can go over 300,000 miles even on the original clutch.
 
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"Do you think that a cluster from a manual would avoid the resistor trick ?"

Yes, it probably would, but the odometer is cluster specific and there is a 130k like discrepancy between the two I have.

It sounds like he already has a manual cluster. He's going to install resistors to make the automatic cluster work.

I think he should just install the manual cluster. He says he's going to give the car away anyway.
 
It sounds like he already has a manual cluster. He's going to install resistors to make the automatic cluster work.

I think he should just install the manual cluster. He says he's going to give the car away anyway.

Correct. I have a manual cluster. I just wanted to try and keep the original odo reading since it only has 130k miles on it.

But it is proving to be a pain in the butt to get it to work 100%, so I'll probably throw in the towel and use my old manual cluster.
 
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So I ended up swapping out my old manual ECU with the auto one as well as the instrument cluster, based on a good P5 expert friend's advice (the ECUs are in fact different).

Now I'm seeing an odd issue where the engine jumps up to an idle of 2k rpm on a cold engine and about 1500 on a warm engine only when the clutch is in AND the car is in gear (e.g. neutral switch related).

Image below of the rewire I made:

trannywire.PNG


I'm gonna dive into it some more after the holiday, but I'm pretty sure some additional rewiring needs to be done with the harnesses...
 
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So sorry to bump this thread. I just wanted to give a final follow-up to the project.


Don't be sorry, in fact, its almost a requirement. It helps us all learn.

Is your car running now?
What did you do to get it running?

Do you have any advice for this guy?


 
Don't be sorry, in fact, its almost a requirement. It helps us all learn.

Is your car running now?
What did you do to get it running?

Do you have any advice for this guy?




So as mentioned in my past posts I ended up swapping theamual transmission into the car along with the manual ECU and cluster, all from a 2002 P5. It took a good bit of wire harness rerouting, but it finally works fine! I tested the dog snot out of it after fixing the 2k idle issue (which was happened because I forgot to rewire the neutral switch to the correct, new ECU pin) and actually got it inspected for rebuild, titled and sold! So she's gone and I'm on to new projects (threads coming soon).

Before I call this thread done though, I will do my best to put a reasonably detailed list of wires that needed to be spliced in order to get a manny swap working. It may take me a bit, since my buddy across town owns the car now, but I will get it done.

As far as the automatic issues are concerned, the problems I had ended up being a mix between clogged up valve body and worn transmission clutch plates. The transmission specialist said it would likely need a total rebuild but he could take off the valve body and deep clean it for cheaper. Since I had the manual (and wanted to try it "for fun") I went that route instead.
 
Do you happen to know if only certain ECUs work with an automatic transmission with Tiptronic?
 
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