bad earth issues

[oliver9523]

Hi folks,

A couple of weeks ago I pulled over in a petrol station, went to start it up again, and got nothing. Called the RAC out, matey traced it to a rotten earth wire from the gearbox. He replaced it and it worked fine.

I went to start the car after work on Monday and got nothing but a bunch of clicks.
Called Mr RAC man out, he refitted the earth lead to a better place and more securely, but the immobiliser was an absolute pig, spent an hour trying to get it to disable. Finally leaving the key in the ignition in the ON position for about 10-15mins sorted it and it fired up.

Starts no probs now. But I did notice while driving home that the little green gear change icon is now constantly illuminated.....?

Has anyone come across this before?

It's a 2002 ph2 172

 

[MicKPM]

The gear change warning light on is normally due to poor gearbox earth OR the earths behind the NS head lamp.

Mick

 

[coxxy]

ive got this green light on too.

 

[coxxy]

what earths am i looking for behind the NS headlight??

 

[coxxy]

no signs of wear in the cables, they all look fine. Let mr know if you get this sorted oliver

 

[Jonny1*2]

is the main earth at the back of the gearbox ok? The headlight one is the same as the negative battery wire.

 

[coxxy]

just took it of and give it a clean. light still on

 

[MicKPM]

But have you actaully "Improved" the earths condition? The only way to know how effective an earth is would be to measure its resistence before and after. Also, it may not actually be the earth connection itself but an issue somewhere else such as the cable itself being trapped somewhere or a poor connection at the ECM itself.

Bring it over to Nottingham if you like and i'll gladly sort it out for you... not exactly close by I know but you're not miles away either.

Mick

 

[coxxy]

where do i test the resistence??? Which 2 points do i put the meter across.

 

[MicKPM]

The earth you're testing and its source which in this case is the battery Negative pole. Bare in mind you're never going to get zero Ohms as your test meter and leads will add resistence but obviously you want as close to zero as possible... normally 0.03-0.5 Ohms is acceptable. High resistence doesn't always mean the earth point is duff though and a poor wire can give this result so bare that in mind IF you do get a high reading.

 

[coxxy]

got 0.08 on the one behing the headlight and the one on the back of the box by the diff

 

[MicKPM]

Then earth condition and continuity isn't the issue for that position. Check the earths for the ECM and UCH... start in the engine bay junction box before going back further inside the vehicle as you may need a wiring "pin-out" for that.

 

[coxxy]

where are the ecm and uch

 

[MicKPM]

ECM is under the bonet and the UCH is near the glove box under the dash.

 

[coxxy]

sorry to sound stupid but is the ECM your on about also ECU??
The one under the glove box, which is the earth pin? Can i just take the connector out without causing problems?

 

[coxxy]

heres my original thread from ages ago
http://www.cliosport.net/forum/showthread.php?582139-SERV-light-and-Green-Gearstick-light