Under Bonnet Fuse Blowing

[christopher1964]

I have an 2003 Relay 2 litre HDI.  I hope someone can help as I have half the van apart trying to locate the problem and have now found this website.

 

The problem is that the Speedo stopped working, mileage is not increasing, reverse lights not working and have an aftermarket rear proximity reversing alert, which has also stopped working.  The engine auto-diagnosis warning light also remains on (I have tried to reset this but it still reamins on)  I also have had a towbar fitted with relevant electrics.

 

Have found under bonnet fuses number 11 fuse has blown when replaced just blows instantly on ingition being turned on (in owners handbook fuse no. 11 says it is ECU, but on underside of fusecover this fuse is shown as an openbook and there are 2 other ECU fuses there as well which show the normal symbol for an ECU).

 

Have wired up a headlight  bulb into number 11 fuse and with ignition on have tried to disconnect lots of things hoping this would show me the fault, but nothing has showed.

 

I have found that by removing no. 18 ECU fuse that the bulb goes out.

 

I am hoping it may be a speed sensor or something similar and not a broken ECU.

 

Does anyone have any advice on this.

 

Many thanks  Chris

 

 

[coastline taxis]

your all over the place with your question so lets start afresh.

 

Your speedo stopped working       was all other sytems fine up till then.

 

did you then start pulling fuses and the other faults appeared

 

was towbar fitted before or after the faults came on. and when you tried to take the mil light of what codes did the scanner come up with.

have you checked the 2 incab fuse boxes for blown fuses.

 also using a bulb wont help much as a lot of the systems arnt 12 volts so wont show up with a lamp. always use a multi meter

[christopher1964]

Yes, Speedo stopped working whilst driving along motorway, at the same time I noticed ECU auto-diagnosis warning light came on.

 

I then started to look at the fuses.

 

The towbar was fitted a year ago.  I have not used any scanner.  I have checked all the incab fuse boxes for blown fuses and have looked for any wires shorting out.  The reversing lights also don't work, but today they did come on briefly and then didn't work again.

 

Would know where the Speedo sensor is on the van?

 

Thanks

Chris

[paul.h]

The reverse light and rear parking sensors not working are probably related and this could be the reverse light switch which may be on top of the gearbox.

 

Often the speedo is taken from the abs sensor system so you could check the abs sensors and their wiring but it could also be taken from the gearbox differential - so if there is a sensor there you could also check its wiring. Your best option will be to have the fault code read since this will be a start on what may be at fault but it is likely to be showing the speed fault since this is needed for the ecu as part of the emissions control.

[christopher1964]

Hi paul thanks for the help,i have checked switch that is on gearbox, wiring looks ok but how do i  check  switch itself ?and where do i find abs speed sensor? .by the way I have a multi metre.iI have traveled down france and now on south coast spain.another strange thing has happend that on tickover it sounds like there is a golf ball boberling around in the small baffle or cat part of exhaust pipe ,goes when revs above tickover is this the baffle comming apart ?.iam ordering russeck manual for my van so to help maintain it,and to help get to botton of current niggles.Any further help is most welcom.many thanks Chris

[paul.h]

If the reverse switch has a single wire connector, all it will do is to earth its electrical supply when reverse is selected - you can check its wiring by pulling off the electrical connector and earthing it - if the reverse lights then come on you know the switch needs replacing. You could remove the switch and holding it to an earth point, push in its plunger to see if it works to put on the lights or check between its electrical connector pin and its body for continuity with the meter.

 

If the switch has a 2 wire connector, you should be able to bridge the connector and the lights should come on if the wiring is ok. Again you could check the switch with a meter across its pins for continuity when reverse is selected or if you remove the switch, push in the plunger to see if it works. It is possible the contacts inside the switch have worn/become dirty or the plunger may have worn down so it is not pushed far enough to work.

 

You may be right about the exhaust and may be just disconnecting it the loose bit can be removed. If the exhaust has been recently replaced it could also be a bit of loose exhaust cement which is often used to help seal the connections.

 

On the speed sensor, if you give the engine bhp and number of forward gears, and if your van is a mark 1 or 2 Relay, it will be possible to say if the speed is from the gearbox or abs sensors (these are on the wheel hubs/brakes).

[christopher1964]

thanks again paul for your help.the van is 03 plate 86bhp 5speed 2.0 HDI. The plug I disconected on top of gear box i think it was 3 pin.i poped into local english macanic garage here in Nerja he said to put it up with drive wheels in the air an run it in gear while pluged in to diagnostic and that would tell weather speedo or sensor is at fault ,when i ask the cost for this he said free as it would  only take 10 mins,does this sound just too nice,any way going up on thurs ,i will let you know how it goes.meanwhile i wil get under it tomorrow to look at reverse switch .many thanks chris

[paul.h]

If it does not cost anything then it must be worth a try. The reverse switch though would not need the engine running to check it, the lights would work with the ignition on so the dash lights up but without the engine started.

 

I think the speed is taken from the gearbox differential on your van.