Corsa ECU problem

ECU fault. Fault in the wire (unlikely). Pump only meant to be run on 2.5V (probably not).

Are you sure that 'when you try to start the engine', the battery voltage is not dropping to 10V, and the pump staying at exactly battery

• voltage?

Thanks Ian,

I've just had another check and the battery voltage does drop to 10V during cranking so the ECU isn't grounding the coil at all. It's staying at the battery's +ve voltage like you say.

I changed the battery for another that I've got that's fully charged (not been cranking the engine all day!) and that only drops to 11.5V during cranking but still no change in the coil grounding voltage from the ECU.

I'm pretty certain it's not the wire from the relay to the ECU because I can get good continuity between the relay socket and the ECU connector for both sides of the coil.

It is looking more and more like an ECU fault...

James

It is behaving differently from the way it does when a key without a transponder is plugged in? I.E. it isn't a dead key? The injectors are the logical thing to swictch off in that case, but I suppose some odd person might choose the fuel pump.

My key is just a plain vanilla one with no transponder built in. My car's at the very cheap end of the range. No electric windows/ power steering/ anything else remotely fancy.

As far as I can tell, the ECU is receiving all the right signals but just isn't grounding the relay. I could drive it to a garage to get it looked at by manually grounding the relay but that raises some serious safety concerns if I were to crash...

James

Wire to headlights, turn on headlights to ground relay, and turn on fuel pump. In the event of crash, turn off headlights.

I notice several hits for the search corsa ecu on

Probably ECU but could be earth problem to the ECU so it cannot ground the relay correctly.

Graham

That would do the trick! I was thinking something along the lines of wiring it to the cigarette lighter so I could yank it out if needs be. Hopefully I won't need to drive it like that!

I'm already scouring the net for replacement ECUs but none of the ones on Ebay seem to be the right make. I'll post again when I manage to find one.

James

Funny you should mention that, Graham. When I was taking the ECU wiring harnesses off I noticed that mine didn't have the earth cable that the Haynes manual showed. Despite that, though, there's good conductivity between the ECU (metal) casing and the battery negative terminal so I don't think that's the problem.

James

Have you tried a new relay?

I've seen faulty relays, that work fine when connected directly to a battery, but ECUs won't switch them (the ECU is only designed to provide x amount of current, and if the relay pulls any more, the ECU shuts down the signal to protect itself, but it doesn't always register a fault code). Also connecting things like test lamps can trigger the same fault.

Also, is it a new or old style corsa, so I can dig out the proper wiring diagram?

Hi Moray,

It's the old style Corsa with the Motronic X10XE ECU. As it happens, the fuel injector relay and the fuel pump relay are identical so I swapped them over earlier today to see what happened. Nothing, that's what :-)

I've not checked the current drawn when they're working but both relays have the same resistance across the coils (within a couple of percent) and both work when connected manually to a 12V supply.

I'm assuming that there's no fault code stored in the ECU because the light on the dash goes off once the engine is started (when manually grounding the relay). I might be wrong about that, though.

James

James Larkin wrote in news:443fe79d$1_2@mk-nntp-

Might be worth looking at if the earth cable was a later modification to fix the problem you are having.

I've been having a look at other people with similar problems and some people seem to think that ECUs can be damaged by moisture getting into them. It may be coincidental but the night before the car didn't start I left it out in the rain rather than put it in the garage (where it's normally kept).

Do you think that the two may be connected or am I just finding meaning in unconnected facts?

James

I've just been out to have a closer look at my ECU and it seems that the cable shown in the Haynes manual connects to the same part of the case that's already grounded on mine. I've checked the continuity between ECU case and battery -ve terminal on mine and there's no change as I crank the engine so I can only assume that the ECU is properly grounded.

Cheers, James

Well, I've got some very different quotes for an ECU. The Vauxhall main

Why? If it's the same engine model?

Being a scrap yard, you'll probably only get one key, and not necessarily the key he'd want to use (i.e doors, boot etc). So he'd need to get his keys programmed into the immobiliser.

I thought he said earlier that his keys had no transponders.

Possibly he did, but all Ecotec engines do.

I've not got transponders in my keys but as I understand it, the ECU stores adaptive values for things like the idle speed stepper motor. I know that these settings need to be erased when changing the motor so I assume that the same will need to be done when changing the ECU.

Please feel free to correct me on this though,

James

necessarily

You *will* have chipped keys.

The ECU stores adapted or learned trim values for idle speed, and timing advance. Disconnecting the battery or changing the ecu would require it to re-learn which is an automatic procedure for it.

Anyways, you have systematically and correctly diagnosed your ECU as apparently not grounding the fuel pump relay to run the pump.

I would suggest your next plan of action is:

a) double and triple check that all earths are present on the ECU multiplug, NOT just the case, and have neligable resistance.

b) If a) is good- have the ECU checked by your nearest ATP dealer.

A replacement ECU will need to come with the keys it is coded to (or recoded by a dealer) but will have to be re-aligned to the instrument panel in anycase.

Tim..