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Reference circuit testing without unplugging all the sensors

  • dhodges
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11 Oct 2020 04:20 #43724 by dhodges
In one of you videos you mention that you have a method for finding what is pulling down the reference circuit without unplugging all of the sensors on that circuit. Where can I find that video?

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  • Tyler
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11 Oct 2020 10:32 #43726 by Tyler
Pretty sure you're talking about the Bad Engine Computer Testing series:

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22 Oct 2020 03:38 #43901 by Flatrater
I haven't seen the video, but here is something to think about.

The loss of the reference can be a number of things. An open wire, excessive current due to a wiring issue or component. Or, it could be a bad module.

Technicians traditionally unplugged everything they thought was using the reference to narrow it down. Done that a million times myself. Another method is to cut reference wires at the module to see if the 5v came back (out of the module)

A better method IMHO is to use a current probe on the circuits from the module. That would differentiate between these faults.

I have a low amp probe which is a bit pricey, but you should be able to do it with a cheaper higher amp probe as well.

Some rough numbers... Most of the 5v reference supply circuits can handle 100-300 ma before the voltage takes a nose dive.

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22 Oct 2020 08:57 - 22 Oct 2020 08:58 #43903 by Andy.MacFadyen
A lot depends on access if you easy access is to sensors unplug them just unplug what you can.. Also another unplug test option unplug the engine harness from the car harness.

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



Last edit: 22 Oct 2020 08:58 by Andy.MacFadyen.

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