C max 1.8 petrol 2004 battery light coming on

Honest John Back Room » Technical matters
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Sat 25 Feb 2017 21:27
C max 1.8 petrol 2004 battery light coming on - johnkent

Right here goes on what ive checked and changed

New battery on

new aux belt on

Alternator charging at 14.1 volts from dash diasgnostics and volt meter

checked main cable to alternator all ok same voltage as battery

checked 3 pin plug stripped back loom no breaks full contunity on all wires well into main loom

cleaned all earth points

changed smart charge fuse with new 10a all ok

Still battery light comes on after 20 seconds of start up

Dont know what else it could be

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Sat 25 Feb 2017 21:49
C max 1.8 petrol 2004 battery light coming on - Badspanner

Alternator is ECM controlled smart charge type (Controlled via same module that controls engine). Battery light on after 20 seconds usually means that ECM has been unable to communicate/control the alternator via the 3 pin plug. it will default into running at usually 13.8v +/- 0.5v volt due to system load, this is true even if the 3 pin plug removed and engine run. After 20 seconds ECM will store a DTC for charging system fault and then send comms to instrument cluster to illuminate battery light.

How far into loom have you checked? water ingress can sometimes travel down loom. Usual suspect im afraid is internal alternator, repair or replace looks likey as you said you've check for multiplug damage and fuses etc.

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Sat 25 Feb 2017 21:56
C max 1.8 petrol 2004 battery light coming on - RobJP

The other day I said it appeared you were playing 'parts bingo'.

I made a suggestion as to a course of action.

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Sun 26 Feb 2017 14:23
C max 1.8 petrol 2004 battery light coming on - johnkent

While i appreciate your reply i'm determined to trouble shoot and fix the problem myself.

Cheers john

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Sun 26 Feb 2017 14:22
C max 1.8 petrol 2004 battery light coming on - johnkent

Thanks for your reply mate

I have undone the loom and traced it as far as the injector loom. where is the ECM located as i'll try and take it back from there it might be further up.

Also someone suggested to check the 3 pin ie: blue and grey wire with a light strobe

Do you know how i'd go about this ?

Also worse ways how involved is it to whip out the alternator to get it checked

cheers john

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Sun 26 Feb 2017 15:22
C max 1.8 petrol 2004 battery light coming on - elekie&a/c doctor

The blue and grey wires go back to the engine ecu,which I think you will find is located behind the bumper,below left headlight.The circuits to both these wires can only be tested accurately with an oscilloscope.

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Sun 26 Feb 2017 15:41
C max 1.8 petrol 2004 battery light coming on - johnkent

How do you test them with an oliscope ?

cheers

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Mon 27 Feb 2017 09:54
C max 1.8 petrol 2004 battery light coming on - johnkent

Does anyone know the Ecu/ecm location on this vehicle, gonna test the samart charge wires from it if i can find it

thanks

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Mon 27 Feb 2017 12:42
C max 1.8 petrol 2004 battery light coming on - elekie&a/c doctor
Ecu on petrol engine cars is next to the battery
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Mon 27 Feb 2017 12:54
C max 1.8 petrol 2004 battery light coming on - johnkent

cheers mate

I presume its the black box on the batterys left as you look front on

Am i right in presuming the blue and grey wires from 3 pin smart charge alternator wire go into the ECU

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Tue 28 Feb 2017 18:42
C max 1.8 petrol 2004 battery light coming on - johnkent

Seem to of fixed it, took the ECU out unplugged it checked smart charge wires for breaks with continuity meter none all good, cleaned up all visible earth points put all loom back took of negative lead run wire to positive to clear ecu memorys started it up no light 1 minute later up came light

took it for a long run to re set all values light went off and stayed off

So somewhere in that lot was the fix

Thanks for everyones help



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Tue 28 Feb 2017 22:07
C max 1.8 petrol 2004 battery light coming on - liammcl

Great job !

Cheers
Liam

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