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Pred247

ECU Power drain

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Hello,

I had an auto spark check my car over recently, due to the battery drain issue. He told me the ECU was drawing half an amp whilst the engine was switched off. He feels this could be the cause. Is half an amp much?

I know the ECU needs a constant power supply to keep the memory retained, but what is the normal drain?

He wants to have the ECU sent off for testing.

Thanks,

John

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Half an amp sounds like quite a lot since the ECU isn't doing anything when switched off (keeping the trim settings etc in a low power static RAM should be negligable). Half an amp is more than leaving one sidelight bulb on. I would've expected less than 100ma for the whole car but that's not based on any measurements at this time of night! I can check mine tomorrow.

Is he absolutely sure that it's the ECU?

Edited by scoule

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Half an amp sounds like quite a lot since the ECU isn't doing anything when switched off (keeping the trim settings etc in a low power static RAM should be negligable). Half an amp is more than leaving one sidelight bulb on. I would've expected less than 100ma for the whole car but that's not based on any measurements at this time of night! I can check mine tomorrow.

Is he absolutely sure that it's the ECU?

Hi there Scoule,

He is very sure that's where the drain is coming from. He thinks it's a fault on the ECU which is leaving a relay open somewhere.

It doesn't mean a great deal to me. Although, now you have compared it to leaving a side light on, I have something to gauge it on.

Thanks,

John

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Hi All,

The ECU is not able to draw 0.5 Amps at standby.

Have you completely removed the ignition-key ?

Are all doors shut ? (the rear hatch-boot-light switch has to get disconnected !)

Radio fuse removed ?

....

If your really want to measure the ECU only, just measure it at the ECU/ECM-fuse. Remove the fuse, insert your Multimeter (Ampere-Meter) instead of the fuse and voil

Edited by Paula&Marcus

Marcus

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John,

Its B2 (5A), located in the rear fusebox, next to the battery.

Cheers

Marcus

www.PUKesprit.de

Hi Marcus,

Is that fuse B2 and B6?

John


Marcus

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John,

Its B2 (5A), located in the rear fusebox, next to the battery.

Cheers

Marcus

www.PUKesprit.de

I just put the tester on it. It came up at 2volts. If I'm honest, I don't know what setting to put the tester on for milliamps.

John

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John, you need the meter on "current DC" range it is probably marked as A with two small lines at the side of the A one is dotted.

If you manage to get the test sorted and you are 100% certain it is the ecm then it will probably be the 12volt to 5volt power regulator section that's gone belly up,this part of the unit is standard electronics that I work with almost everyday,if you get really stuck in finding someone to repair it for you drop me a line and I will sort it for you

cheers dave


Dave Hopwood

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......this part of the unit is standard electronics that I work with almost everyday,if you get really stuck in finding someone to repair it for you drop me a line and I will sort it for you

cheers dave

This is another fine example of what makes this Forum and community so strong. Fellow owners what are prepared to help out other owners, just because they can.

Great to see ! :)

Edited by mike_sekinger

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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Mike is so right. This forum has been fantastic to me. Makes me wish I could give more imput for others.

Goodness knows I couldn't have done the injector job recently without the help and support on here.

David,

To enure I don't waste anyones time, I've attatched a pic of my tester. I can see the A with a line and a dotted line. It's at 2 O-clock. If I select that part of the tester I can't get any reading at all.

Would you mind telling me which one I need to place the dial on and which slots I need to plug the probes in?

I just want to be sure I get it right, rather than waste everyones valuable time.

Thanks David, you're been a gent and your offer is really appreciated.

John

post-1853-1202830617.jpg

Edited by Predator

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black in middle, red right or left (depends on what you want to measure 10Amps power circuits or in the fine electronics milliamps range)

#round switch from 10Amps variable down to the range of 2000micro Amps range in display

right ?! What is in the instruction book ?! :)

Alternated current is the 200-600 volts range upper right. Directed current is from 600 to 200milli volts upper left. resistor is lower left. the circuit check is with a diode as a one way switch (speaker sign right lower side) and the rest is for transistors and "Base, collector, emitter Checking"

wait a moment , i have something forgotten: "hold" is for display view *freezing* -it does show the last digits in the display. and Backlight is for dark nights on the side of the motorway -for all who want to measure a car or something else outside a home/garage.. :)

Edited by G

*********************************************************************

to name the things if I see them, that's what I call integrity..

*********************************************************************

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As you are talking about a half amp (0.5 A) current draw you should start in the 10 A range. 200m = 0.2A. Put hte black testing wire in the COM socket and the red one in the left 10 A socket. Be carefull for testing currents of more than 10A because those connections are unfused. Set the dial to 10A and start measuring. The numbers to which the dial point are the maximum values measured/displayed. If you want to measure anything else you should use the middle (COM) and the right socket, except if you use the NPN/PNP setting which is for use of testing transistors which use the EBCE socket.

You probably blew the fuse in the meter as you are not getting any reading. The right socket is probably fused with a 200mA fuse. Replace the fuse and the other settings should be working again.

Freek


Esprit Freak

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John,

I would play safe to start with and use the 10A range(as we suspect it's going to be around 0.5A anyway)So as Gunter said black lead in center red in left range on 10A DC.

Pull the ecm fuse in the boot compartment fuse box,place each of the meter probes in the socket you have removed the fuse from,don't worry which way round the probes are the reading will be the same value ,however,one way will display a minus sign on the display.Make the test,the resolution on the 10A range will be fine if the ecm is faulty and you are pulling a genuine half amp.If the results appear to be just zeros do the test again this time with the red lead in the 200mA range if the reading is something like 002 this would indicate that the ecm was drawing 2mA and is probably fine.So thats about it

good look!

dave


Dave Hopwood

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Thanks for the replys everyone.

I've done as was suggested, but I'm still getting a reading of 0.00

I've also changed the fuse.

If I turn the dial to 20 which is in the top left corner, I get a reading of 1.95 This is the only way I can get any kind of reading.

Do you think it could be a faulty tester I have?

John

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disconnect your battery cable (only one) an fit the tester "inline" . switch round selector to DC 10 amp and look that you have an overall Amp flow for all steady circuits together. maybe you have the red in the wrong socked ?!


*********************************************************************

to name the things if I see them, that's what I call integrity..

*********************************************************************

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Amp measurement is always "inline" of a circuit (you have to open the circuit and fit the tester direct into the circuit line), Voltage is "around" (parallel) to a part of an electric circuit (for example a resistor, bulb, or other stuff).

OK ,That's all basic stuff... . I'm not a qualified teacher after all :D


*********************************************************************

to name the things if I see them, that's what I call integrity..

*********************************************************************

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I cant comment specifically on the Esprit ECU but others I have known are microprocessor based controllers. When the ignition is off they go into a standby or 'sleep' mode where only a few timer/interupt routines are maintained. In this state the unit will only be drawing mA or less.

If I turn the dial to 20 which is in the top left corner, I get a reading of 1.95 This is the only way I can get any kind of reading.

In this case you have about 2mA which is what I would expect for correct operation?

However, I did have an experience (BMW318) where the ECU could draw 300mA depending on how the battery was reconnected. In the end I made a parallel socket so I could connect an ammeter instead of the fuse while reconnecting the battery.

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..If I turn the dial to 20 which is in the top left corner, I get a reading of 1.95 This is the only way I can get any kind of reading.

top left 20 is Voltage range of 20 Volts , nothing you are interested in !


*********************************************************************

to name the things if I see them, that's what I call integrity..

*********************************************************************

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The best way to test inline is to pull the fuse out, and with the multimeter in AMPS (at the highest setting) connect the test probes to the metal holdes either side of where the fuse was. If the circuit is off or dead then the meter will read 0.00

If it is drawing current then you'll see a value on the display

TBH John if you're not sure get someone to help who knows what they are looking at - no offence and all, but when testing current you can cause short circuits that might do further damage, esp if you are prodding and hoping - plus you dont sound as if you're totally happy with the readings and what they mean which is just going to go around in circles.

Again, not being rude or anything - everyone has to start somewhere but your best bet is to get someone to show you what it all means which would take 1000x times quicker than typing it all out on the forum :respect:

If you're local I don't mind showing you.

As I say when you connect the leads in the 'current testing mode' the meter becomes a direct link from one probe to another - if you put that across the battery you'd blow the meter up ! I know trained sparkys that have left a meter on Amps and then put it across 415 volts accidently....didn't half make them jump !

If the ECU is drawing 0.5amps at rest (which is should only draw 0.005 at the most really) then there is either a fault with it or the diagnosis is not correct.

I juuuuuuust wonder if you have a light on or something - the V8 has courtesy lights doesn't it in the doors and under the front comparment, check there 1st if you can - manually push all the switches that activate the shut off and see if the lights go out. It's very rare the ECU fails.

Edited by Jonathan

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Hey Jonathan,

I've far from taken offence mate. I agree wth what you say. That's why I did get a sparky to check, and he confirmed there is a drain from the ECU.

Because I was not there when the test was done, I don't know how he performed it. Because he openly said he did not know the ECU wiring, I was concerned that maybe all was normal but he was not aware of just how it works.

I have checked all the interiour lights, and even disconnected them, just to be sure.

I think I will simply whip the ECU out of the car and have it sent for testing. The sparky who found the fault said that testing it should be about

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Whip the ecu out by all means, but before you send it off to be inspected monitor your battery drain issue with the ecu unplugged.

If the battery is still going flat with the ecu sitting on the garage bench, chances are something else is causing the drain and to be frank, there's not an awful lot of eletwonick twickery in an Esprit so it shouldn't be too hard to track down.

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Well I hope it's not the ECU, I'd be suprised if it was, they are generally very well behaved.

Just a quicky - I still have a lot of notes from my old V8 days, the ECU is from B2 fuse but also is the hot soak pump relay.

I wouldn't be at all suprised if the fault lies there - it's called the recirculation pump relay. Basically the V8 has an auxillary pump which continues to circulate coolant after switch off to stop the engine overheating when you've been nailing it like a looney all over the place.

This is a known area of modification as an update was scheduled for the V8 during 1998 iirc - the modification was done on the wiring as per the schedule. Given how I have seen people do wiring on cars I would definatly have a sniff around this area

If you're metering across B2 (fuse for the ECU) you could get a false reading through this circuit which could trick you into thinking it's the ECU.

The solution would be easy - remove the relay (I THINK it is the top left relay on the relay board near the battery).

If it is the case your current draw would drop significantly - and problem identified.

Does your sparky have the wiring diagrams for the car ?

Are you anywhere near the south east ? If so you could pop by and we'll have a look see.

Edited by Jonathan

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Well I hope it's not the ECU, I'd be suprised if it was, they are generally very well behaved.

Just a quicky - I still have a lot of notes from my old V8 days, the ECU is from B2 fuse but also is the hot soak pump relay.

I wouldn't be at all suprised if the fault lies there - it's called the recirculation pump relay. Basically the V8 has an auxillary pump which continues to circulate coolant after switch off to stop the engine overheating when you've been nailing it like a looney all over the place.

This is a known area of modification as an update was scheduled for the V8 during 1998 iirc - the modification was done on the wiring as per the schedule. Given how I have seen people do wiring on cars I would definatly have a sniff around this area

If you're metering across B2 (fuse for the ECU) you could get a false reading through this circuit which could trick you into thinking it's the ECU.

The solution would be easy - remove the relay (I THINK it is the top left relay on the relay board near the battery).

If it is the case your current draw would drop significantly - and problem identified.

Does your sparky have the wiring diagrams for the car ?

Are you anywhere near the south east ? If so you could pop by and we'll have a look see.

Hello mate,

I'm based in Surrey, which is about 50miles away. If you're around in the week, I would really appreciate that?

You gotta love this place. :cheers:

Send me a PM if you want and we can sort something out.

Thanks again,

John

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Only prob is you'd have to come here - I dont have any wheels at the moment (2 esprits and none of them work :cheers: hawwww - Lots Of Trouble Usually to do with the bloody owner !)

Today is not good we're working on stuff and I need to go running for a few hrs but tomorrow shouldn't be an issue.

Got all the tools / wiring diagrams here but if you wanna bring your multi meter I'll show you how to fly that as well - we'll try Grahams suggestion too, although it's probably not a good idea taking the ECU out of you wont be able to drive the car :D

Upto you - if you think it's worth the trip then I'll see what I can do, if not I dont mind sitting on the phone one day when your sparky is having a prod as it should be a fairly easy spot - thats the issue, you might make the journey and we'd have it cracked in 5 mins hehe.

Lemme know - PC's on all day and I'm in and out all day.


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