Got in my RRS with 3.0 Diesel yesterday and the engine wouldn't start. The cluster was lit up like a Christmas tree, with warnings for essentially every system as "not available." I suspected the battery, as my scan tool was showing 11.5 volts, but the battery itself was 12.4. Strange. That sent me down a long rabbit hole thinking that either the Gateway Module or the Battery Maintenance Control Module might have failed, but both seemed OK.

I decided to check the front and rear fuse boxes for blown fuses, since the ECM and TCM weren't showing up on the scan tool. It seemed like the high speed CAN was down, except that ABS was still showing. All the fuses were OK, so I immediately thought that perhaps the ECM had died. I pulled the connectors for the ECM and found this:






Seems crazy that water could get in, but then I noticed that the rubber trim that sits in the front fender (Wing for UK guys) channel is basically made of foam rubber, which acts like a sponge and soaks up water. The edge of the rubber trim sits less than a centimeter from the ECM connector. I can easily see how water could wick through and drip down onto the connector, ruining it.



I removed it and squeezed and a huge amount of water came out.



What a massively stupid design and choice of material. Now I've got to chase down a used ECM and find somebody that can code it to my car. I'm also going to have to pick through that connector and remove and replace a bunch of those female pin connectors.

For a vehicle that's supposed to be all weather, this is really a shame.

So I pulled the connector apart today to make sure that the pins are good. To get into the right pin, I had to unwrap the electrical tape and the protective sleeve to make some room. Once I did that, I pulled the wiring apart to get at the wire which was affected most by the rust. It was a ground wire, which explains why it caused so much havoc on the instrument cluster.

To get an individual wire out is a two step process. First you pull the plastic retention pin (the purple one in my case; there is a red one on the other side for the larger gage wires.) Next you use a small pick (I used a safety pin) to push the connector release and pull the wire out from the back. I then used the safety pin to push the rusted pin out from the female side of the connector.

I bought some DeOxIt D5 which didn't come in the mail until later today. I'll spray down the connector really well to get any smaller corrosion out. I did pull one of the old male pins from the Oxygen Sensor that I recently changed, and used the pin to push through each slot on this connector, to make sure any large bits were cleaned out.






I mailed the ECM to a guy in Plymouth. He's supposed to turn it around in 4 days. We'll see.

The ECM came back and I plugged it in, but the vehicle was acting the same way as it did before I sent it off. I hooked up the scanner and tried to clear the codes, but they wouldn't clear. I had a brief moment of panic, but figured it was just another puzzle to figure out.

I went inside and drank a beer and thought it over. I decided that the faults were probably stored in the modules, and since they weren't currently believing that they could communicate, the scanner wasn't going to work. So I disconnected both terminals from the battery and let it sit for about an hour. I also pulled the side panel from the rear compartment because I thought this had an auxiliary battery (for the stop/start system) back there which would also need to be disconnected. But there wasn't one there which was a bit of a surprise. Anyway, I hooked the battery back up and it fired right up. Success!

Click image to enlarge

Great result  Range Rover Sport (gone): Mercedes S63 AMG Coupe: 992 Porsche Carrera 4S: Range Rover Fifty P400e

Glad you got it sorted in the end although I think I would have gone into meltdown when you plugged int back in and got the same faults!

Well done for fixing it and thanks for taking the time to document it, hopefully will help others out. 2016 RRS SVR Estoril Blue
2005 4.2L Supercharged Java Black - gone but was my first love.
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If we all point our RR's in the same direction and accelerate at the same time can we turn back time?

Is there not supposed to be a plastic cover over it as well? Joined the X5 45e club
1994 Defender 90 300 tdi

Yes, there is a plastic cover over the ECM/ECU, but I had it removed to show the location. It is held in by four screws. But it's not "water tight" and I can see how water can get in there. I will never understand why manufacturers put the connectors on the top of the modules instead of the bottom or the side. It's just a recipe for disaster.

Thanks, think I’ll take a look Joined the X5 45e club
1994 Defender 90 300 tdi