I'm looking for advice concerning water getting to my ECU. Over the last couple of years I've had problems that cause the engine to go into the dreaded "restricted power mode" and then completely shut down shortly afterwards. Only happened when it was raining or mild temperatures with snow. The dealer was unable to diagnose the problem, (4 times) probably because the car would sit in his garage for about a day or so before they could get to it, and it would be dryed out by then. It looks like we finally figured it out but how do I prevent if from reoccuring. Any products or procedures that you guys can recommend to seal the thing up? (2003 S-Type V8)

 

Don't know about an s type (check with others on here) but i have used ignition sealer spray products on other cars with water ingress problems interfering with the electronics.

Something like this
CarPlan Car Care - Ignition Sealer & Power Start

I would try and find where the water was comming in fiirst and fix that.

 

More than likely the water is running behind the black plastic wiper cowl. Other members here have used silicone caulk between the windshield and the black cowl. I believe member eds123 did a write up with pictures, if my memory serves correctly.

Make sure all black covers are sealed that hold down the cowl as well.

 

The ECM is inside the car and is most likely NOT getting wet. Your symptoms point to the throttle body/TPS getting wet. Throttle body can be rebuilt much cheaper than new. TPS is just replacement only.

As was pointed out the rubber seal under the clips that hold the cowl cover on has been found to leak water almost directly on the back of the engine where the throttle body sits. Your TPS is plugged into the throttle body and your problems could one or the other or both items.

See attached TSB on what to check and where to seal things up. You can do it yourself just be aware that if the TPS and/or throttle body have been wet repeatedly you still might need to replace them. I would for sure at least open things up and spray some water displacing spray into the connections. As well as making and breaking them several times to remove the corrosion.
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Thanx "tbird6" but t'aint the throttle body, that's the first thing that I checked. I have the T.B. sealed up tighter than a horse's *** in fly season and still had the issue. Definitly the ECU.

 

As I recall, some time back, a fellow member had the OPs issue. Water had been leaking between the cowl and windshield, causing water to fill into the cabin/pollen filter box which leaked into the vehicle and the ECM. It was a while ago but maybe one of the long timers here will remember who, what and the when.

 

Might be worth while looking through this thread on Jagaur forum uk Jaguar Forum.co.uk • View topic - Multiple errors & no start-up

 

Thanks for the link but it just reinforces what I said. It is EXTREMELY rare to have ECM problem. In fact that is the only verified one. Can you post pictures of your wet ECM?

Like that thread said I can't see how water would get to the ECM. I have had it out and it is very well protected.

Did changing the ECM fix your problem? Did you repair or replace the ECM?
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clubairth1, if you open this link there are pics there or can you not see them?

Jaguar Forum.co.uk • View topic - Multiple errors & no start-up

It was not me that had the problem but a fellow member Trevor on the site, he has not found the leak but he wrote " I spent the afternoon sealing the module and re-fitting it. I have used high temp silicon to seal the module and also applied some to the bulkhead gasket.
After the harness was re-attached I also ran a bead of silicon around the top so any moisture would have the silicon and gasket to get past.

Inside the car the sound proofing showed some slight white staining above the ecu. There is no sign of a leak or damp.

The amount of liquid required to do this amount of damage would not be very much, the reaction between aluminium/steel/water/components with a voltage on is well known, I often see TV sets with liquid damage. I also see no aircon pipes in the area where possibly condensation could arise.
The ecu wiring plug is protected by the gasket and above is a plastic box that diverts the rain water away. Inside that box is another with the pollen filter.
I see no signs of water getting anywhere it shouldn't.
So I am not really sure how or when this happened. But it is old damage that has got worse.
I suppose this could be another case of inappropriate use of a pressure washer...."

I hope this helps he repaired the ECU himself, it had a lot of corrosion.

I hope this helps :-)

 

The car broke down a long way from home so was towed to a FORD dealer located 2 blocks away. Not many Jaguar dealers in the vicinity of Massena N.Y.
When they removed the cowling etc. there was a trace line of water running down toward the cabin filter, ECU area. I saw the part after they removed it and there were several coroded pins - copper oxide green deposits. Apparantly the inside of the ECU also showed signs of corrosion. They cleaned up the mess, reinstalled the unit and the car started up and ran like a charm. *375 bucks was cheap, a new ECU would have cost $2106.00 + labor.
I want to ensure this doesn't happen again.

 

As has been said, water is not meant to get past the cowl/windshield (windscreen) and silicone sealant is OK for sealing it.

The other places water *commonly* gets are the plug wells. Again, lack of sealant somewhere.

I suppose a car whose interior is too often wet could be a problem, such as broken or unused aircon or maybe overuse of cleaner on the carpets?

The PCM being the problem appears incredibly rare, even when there's a water leak at the cowl.

 

It does seem rare, funnily enough I just read Trevors description of his repair this morning and his description is eerily similar to Mattys.

 

No I read the entire thread. I was really impressed with the repair of the circuit board. That stereo magnifier he used has got to cost several thousand dollars!
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Isn't the PCM on the opposite side of the firewall to where the rain water would enter, with the harness passing through a grommet in the firewall? So, the cowl seal and the grommet would both have to leak and the water also travel to and enter the PCM? Is that why it's so rare?

 

The PCM is inside on the right hand side (Passenger in the US) firewall. Right behind the glove box.

Yes you are correct. But it is mounted under the pollen filter/fresh air opening below the windshield. I could see that being the way water could get in. This would bypass the plug weather seal where the wiring harness attaches to the PCM thru the firewall.
Glad you found it I hope it stays rare and unknown!!
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I removed the cowling, pollen filter box, crossmember stress bar, box under the pollen filter box, etc. and used about a half cylinder of silicone to caulk everything, and I mean everything! Then pulled the glovebox and sealed all the seams and screws on the ECU, and them caulked again at the passenger compartment side of the firewall.
That's a lot of sealing but I want to eliminate the potential that this issue will reoccur.
There was an area of rust aprox. 2 in. sq. on the top at the right front (firewall side) of the ECU so we know that water was getting in from the gasket or plug at the engine side.
The ECU is VERY EXPENSIVE to replace so I hope this issue is a done deal.

 

Yep, that happened to me. I had just washed the car at a car wash when the bells and whistles went off. The water leaked in to the cabin filter area, seeping into the ECM. Trash (leaves ect) was also part the blame too. After cleaning out the area, I resealed it and haven't had an issue since.