Hi all,
I just got a 2003 C4S, and knew it "had some issues", but I didn't expect this.

I have been having intermittent fault codes and a (sometimes) poor running engine since I got it (about 3 weeks ago), things like:

P1120 Porsche fault code 117 - Throttle plate
P1122 Porsche fault code 431 - Throttle potentiometer 2
P1121 Porsche fault code 430 - Throttle position sensor 1

11:30 After a drive
P1120 Porsche fault code 117 - Throttle plate
P1122 Porsche fault code 431 - Throttle potentiometer 2
P1138 Porsche fault code 430 - Throttle position sensor 1
P1514 Porsche fault code 540 - Throttle adjuster Lower mechanical stop

At 14:30
P1514 Porsche fault code 540 - Throttle adjuster Lower mechanical stop
P1120 Porsche fault code 117 - Throttle plate
P1138 Porsche fault code 430 - Throttle position sensor 1

Next day First drive:
P0102 Porsche fault code 115 - Hot film MAF sensor
P1516 Porsche fault code 404 - DVE control range
P1502 Porsche fault code 412 - DVE fault during spring test

Cleared, drove 1 mi then:
P1518 Porsche fault code 404 - DVE control range
P1517 Porsche fault code 543 - Throttle adjuster Environmental condition not OK
P1120 Porsche fault code 117 - Throttle plate
P1122 Porsche fault code 431 - Throttle potentiometer 2
P1121 Porsche fault code 430 - Throttle position sensor 1

They are mostly "throttle" related and all of those sensors CAN'T have gone out at the same time...
And I thought "what do they have in common?"

The ECU

So I decided to look at it for visible faults, re-rack/clean the connector, and this is what I found.

What the ECU area is "supposed to look like"




and this is what the relay side looked like:




and under the relays:




I only found one chewed wire (surprisingly) and it was just the wire covering on the big brown wire that connects to the ground stud.

But I did find some blue corrosion on the back of the relay connectors (it looks like alkaline battery damage, is mouse **** alkaline?)

It looks like the vermin is getting in via the wiring harness opening that goes back on either side of the very aft corners of the cabin.

Have you ever taken that interior out? Got any pics/ tips?

What about those of you that have pulled your engine?
Where does that harness come thru into the engine bay?
Can I get to it with the engine in??
(I am concerned about chew damage on that harness)

I am going to get some electrical contact cleaner and try to rinse off the mouse urine, and see if that helps the intermittent DTC's...

Paul

 

As a follow-up, I cleaned out the rodent debris (where did it come from???), took out the relays, cleaned the sockets with a liberal dousing of contact cleaner, put the relays back in, and went for a drive (after reconnecting the battery and waiting for the e-throttle re-calibration).

The car drove fine, and (currently) no DTCs!!

 

Rodents...?

Seriously though, glad the damage wasn't more severe.

 

As a once active guy on this site always said: "It's mice...it's always mice!"

 

Fyi, u can pull the entire harness through the passenger side grommet. Just undo the 2 large electrical connectors in engine bay, rear light harness and a few sensors and just pull from the inside. It will all slide through. The drivers side harness is just as easy but the coolant resi is kinda in the way. U do have to remove a bunch of interior panels and some foam but its not that bad.

 

That is exactly what I was thinking!

I was dreading finding a myriad of chewed wires under the relays. That would have been a very time consuming repair (while in the back seat...)

 

That is great information!
I'll do it when I pull the engine.

I tried tugging on the very aft carpet/shelf (behind the ECU/Relay panels) but it didn't want to come out easily, so I vacuumed what I could, and thought I would see what you "more experienced" 996 owners knew.
I'll get in there again.
This project has started me on a "rear seat delete" mission.
I want to put in a nice carpeted shelf, with cubbies where the lower seat buckets are.
(put the ECU on one side and the relays on the other, in order to open up a larger shelf area???)

I have seen some pics online (RS shelf?? GT3 shelf??) and want to do something like that.
Those seats are useless (as they are in my 74)

Paul

 

Its very corrosive.
Now that you got it cleaned up, I'd treat(spray liberally) all those connectors/prongs/relays/etc, with some WD-40 to stop the corrosion and prevent any more.
Just like "alkaline battery" corrosion, cleaning them is not usually enough, its hard to stop that type corrosion from continuing down the road without an anti corrosive treatment like WD40.

jmo

 

I would should suggest baking soda water mix, spray down the corroded area with the solution then scrub it and rinse it, then spray down with WD40 to repell the water...

Baking soda water mix will neutralize any battery acid/mouse ****/alkaline ...

 

I was absolutely sure this was going to be a post about I ran over a squirrel...

 

SQUIRREL??

 

As a follow up...

I got ALL of the rear "interior" out, found more mouse debris and a bad ground on the passenger side.

(and Rennlist won't let me upload a pic here, see the end)

I am hoping that this bad ground is the "multiple DTC faults" issue. Only time will tell.


The wiring to the rear firewalls (on both sides) looks OK,

I hates meeses to peeses... (that is a quote, if you are old enough)



Bad passenger side ECU ground1




Bad passenger side ECU ground2