Is my ECU dead?

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FlatbedPilot

FlatbedPilot

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And can it be resuscitated? (2004 TD5)

Jumped into the Defender to go to work tonight and switched on the ignition. Loud buzzing starts coming from under the driving seat and the ECU light on the dash didn't come on as usual so I'm assuming that the ECU is buggered? I tried cranking it over but, as I expected, it didn't start.

When I parked it this morning after travelling home from work it was running perfectly although when I'd started it the night before to go to work there was some very slight hunting at idle, which has never happened before.

I had to jump into the wife's car to go to work so I've not had a chance to look at it yet. Just wanting to get some ideas of what I'm possibly facing.
 
Check the relays under the drivers seat as a first step, check for oil in the plug that may be coming down from the injector loom, if bad it can actually fill your ECU.
 
DefenderPilot said:
And can it be resuscitated? (2004 TD5)

Jumped into the Defender to go to work tonight and switched on the ignition. Loud buzzing starts coming from under the driving seat and the ECU light on the dash didn't come on as usual so I'm assuming that the ECU is buggered? I tried cranking it over but, as I expected, it didn't start.

When I parked it this morning after travelling home from work it was running perfectly although when I'd started it the night before to go to work there was some very slight hunting at idle, which has never happened before.

I had to jump into the wife's car to go to work so I've not had a chance to look at it yet. Just wanting to get some ideas of what I'm possibly facing.
Click to expand...

Doubt it, they are actually very robust. As said above, check relays, ECU's wouldn't really have any components in them that could buzz, just a PCB of semiconductors.
 
Cheers for the replies chaps.
I've managed to have a quick look today.
There are two yellow relays next to the fuse box. One of those is buzzing. I tried swapping it with the other one as they appear to be the same and it made no difference. Unplugging the black plug from the ECU made it stop. There was oil in the red plug to the ECU, which is annoying, as I fitted a new injector harness last year when I was heaving all the trouble with the cylinder head.
I have also now noticed that I can't hear the fuel pump when I turn the ignition on.
Looks like the next move is to take out the ECU and open it up.
 
DefenderPilot said:
Cheers for the replies chaps.
I've managed to have a quick look today.
There are two yellow relays next to the fuse box. One of those is buzzing. I tried swapping it with the other one as they appear to be the same and it made no difference. Unplugging the black plug from the ECU made it stop. There was oil in the red plug to the ECU, which is annoying, as I fitted a new injector harness last year when I was heaving all the trouble with the cylinder head.
I have also now noticed that I can't hear the fuel pump when I turn the ignition on.
Looks like the next move is to take out the ECU and open it up.
Click to expand...

If a relay is buzzing then it has probably failed or is not getting enough current to energise the coil and keep it supplied with enough current to keep the relay "on".

If there is oil in the loom a bad connection could cause a reduced feed to the relay which could have the impact you describe.

Another thing is check the little earth wires, in the under seat-box area, if corroded or loose they can stop the relays from switching properly as they form the earth.

Which relay was buzzing, the 4th one along is the "main relay" is this is dead then not much will work including the fuel pump getting it's signal. If you swapped them and it made no difference, so I read that to mean, it still buzzed (if it made no difference) then it sounds like a power issue to that relay. You could jumper the relay terminals on the switch side, this effectively acts as the relay being ON. Only do this if you understand how relays work and how to jump the correct terminals in the relay socket. 5th relay is the fuel pump.

I would not be opening the loom yet unless it is to clean oil from the plugs as I still think there is nothing wrong with your ECU.

Is your battery good?
 
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Battery is very good. Earths seem to be good. None are loose or corroded.

There are only three relays in a row next to the fuse box. 2 yellow and one black. It's the middle yellow one that is buzzing. I'll get a picture up tomorrow after work.
 
Oil from loom between head and ecu will take a while to clear after fitting new injector loom. Check every week and clean appropriately ;)
 
The yellow relay (middle one of the three) is the one that's buzzing.

DSC_0021.JPG
DSC_0020.JPG


I've taken the ECU out and opened it up to check inside. No evidence any oil has got inside.

DSC_0021.JPG
 
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DefenderPilot said:
The yellow relay (middle one of the three) is the one that's buzzing.

I've taken the ECU out and opened it up to check inside. No evidence any oil has got inside.
Click to expand...

You have gone into catastrophe mode, looking for the worst case scenario rather than try and look and the simple things first. The advice given to you above was to leave your ECU alone, you could check the plug externally to see if it may have got oil into from the plugs.

Have you looked into jumping the relays? Do you have a multi-meter?
 
Scooby22 said:
The middle relay is the main rely so that may be the problem.

View attachment 174241
Click to expand...

This is my suspicions as posted above, may not even be the relay but a connection to the coil side is poor and not energising it properly which creates the buzzing noise. I have suggested he looks into how to jump the relay if he doesn't already know how to.

The OP needs to be getting a multi-meter now and learning how to use one I think.
 
Looking inside the ECU to make sure no oil was in it was pretty simple and only took 5 minutes. It's something I can rule out now. The red plug and socket are contaminated with oil so I'll try cleaning them up with a suitable degreaser next. These things are easy for me to do. I don't know about electronics so I'm leaving that for now.
 
So today I've cleaned out the plugs with carb cleaner and dried them with a heat gun. I've also tested the buzzing relay off the car by powering up the trigger circuit and it makes a nice healthy click. The problem persists though. A mate of mine has one of those cheap OBDII scanners that you plug in and connect to your phone via bluetooth. We tried that and couldn't get it to connect to the ECU.
 
DefenderPilot said:
So today I've cleaned out the plugs with carb cleaner and dried them with a heat gun. I've also tested the buzzing relay off the car by powering up the trigger circuit and it makes a nice healthy click. The problem persists though. A mate of mine has one of those cheap OBDII scanners that you plug in and connect to your phone via bluetooth. We tried that and couldn't get it to connect to the ECU.
Click to expand...

OK, as said before, jump the relay socket now - basically manually energise the main relay circuit - your ECU will then turn on and you will probably be able to start it. You know which terminals were the coil so I assume you know which terminal is the NO (Normally Open) one, i.e. the one that goes live when the coil is energised.

If all is well with this over ride, then you can be certain the issue is a bad connection and that relay is not getting proper voltage and current to operate the coil properly. Could be as far up the chain as the ignition switch level.

When you checked the earth connections to the Fuseboard/ECU area did you remove and clean them up or just check they were tight? Either do that, or a quick check with a meter checking the earth connections resistance, should be near enough 0, it won't be but damn close. On a short section it should be 1-3 Ohms really nothing more.
 
I got a loan of a Nanocom this morning so I plugged the ECU back in to test it. When I turned the ignition on the relay was no longer buzzing and I could hear the fuel pump running. So I tried to start it and it started right up like nothing had happened. Weird. Knowing I'm not going to have to fork out hundreds for a replacement ECU is a good feeling though!
I can only assume that cleaning the plug and socket made the difference and it just needed longer to dry out properly.

Thanks for the input chaps
 
DefenderPilot said:
I got a loan of a Nanocom this morning so I plugged the ECU back in to test it. When I turned the ignition on the relay was no longer buzzing and I could hear the fuel pump running. So I tried to start it and it started right up like nothing had happened. Weird. Knowing I'm not going to have to fork out hundreds for a replacement ECU is a good feeling though!
I can only assume that cleaning the plug and socket made the difference and it just needed longer to dry out properly.

Thanks for the input chaps
Click to expand...

Argh... How many times, I told you your ECU was never damaged. You had a bad connection somewhere. As you alluded to yourself, removing and replacing the relay may have cleaned up a dirty terminal.
 
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