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When checking for ECU codes MUST it be an LED light? 


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 Post subject: When checking for ECU codes MUST it be an LED light?
Posted: Thu Nov 19, 2015 12:24 pm 
Oompa Loompa

Posts: 27

Joined: 13th Feb 2007

Location: Sydney
NSW, Australia

Hey all! =)

I was a little apprehensive making a post about such a silly question considering how mundane it really is but i can't seem to find a concrete answer.

This whole time i've been bridging the correct wires and even getting the codes being read on my digital multimeter (which is quite laggy and damn near impossible to read for this test) but when i use either the little kickpanel bulb or the interior globe nothing shows up.

I guess i've just answered my own question ... :roll: that would lead me to the next one, would the only option for a DIY LED test light be to goto Jaycar and buy the correct resistor and light?

Is there no other way to somehow get a regular TestLight to work?

Thanks for reading!! :mrgreen:
 Post subject: Re: When checking for ECU codes MUST it be an LED light?
Posted: Thu Nov 19, 2015 12:38 pm 
Technical Contributor
User avatar

Age: 26

Posts: 3688

Joined: 27th Sep 2006

Gallery: 20 images

Ride: ED Falcon

Power: 133 rwkw

Location: Leeton
NSW, Australia

You have answered your own question... The computers internal circuit resistance is too high to glow a globe... This helps prevent a short circuit occurring inside the computer if something goes wrong on the wiring...

You can by proper LED test lights from auto stores... They're a little dearer but may save you the hassles of making it yourself...

When doing ANY testing on inputs or outputs from the PCM (or any sensitive electronics) you should only be using a high impedance (digital) multimeter or an LED test light... Too easy to blow things up with a globe... That's not to say throw it in the bin... There is numerous things you cannot prove with a high impedance meter and you need either a dummy load, test globe, or analogue multimeter...




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 Post subject: Re: When checking for ECU codes MUST it be an LED light?
Posted: Fri Nov 20, 2015 12:14 pm 
Getting Side Ways

Posts: 2425

Joined: 5th Nov 2004

Gallery: 7 images

Location: Brisbane
QLD, Australia

DOY is easy. jaycar - LED, Resistor. I used test clips, but they also have small terminals there.

Build your test-light into a Pen Barrel and away you go. 5mm LED's work well in the old BIC style pens
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