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Grant Baker

S15 Plugin losing power on cranking

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Hey guys,

Just fitted an S15 plugin to a PS13 Sylvia.

All pins doing as they should etc, but losing 12v to ECU on cranking.

Seems that Pin 38 (ECCS 14v Relay) is losing power on cranking.

Is this normal on the PS13?

Pin 34 is starter signal

Pin 36 is Ignition Signal and is live when cranking. 

Should we swap Pin 38 & Pin 36?

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If you have 14v all the time then it much be either an earth issue OR you are inducing too much magnetic noise, a good test for this is to bump start it, if that works then look at the starter.

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Yes I have seen it twice, both times the earths had been spliced into one and were screwed to a poor ground point (one ground point was painted and one was rusty) , supplying battery voltage direct solved the problem.

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Awesome. Thanks. 

Never had this before. 

Voltage on pin 38 *was* going from 12.4v-10.9v-9.6v-7.7v-5.4v-3.3v. 

So an earth issue may also make sense. 

What is a little odd is that it ran fine on stock ECU. 

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The main grounds are on Pin 39&48, and the main 12V supply is on pin 38 & 47.  Try an aligator clip jumper lead direct to battery to isolate which one of these pins is disappearing when cranking.  Note these two grounds and two power pins are linked together internally so you only need to test one of each.

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Right, the plot thickens...

Jumped the power and earth cables. Definitely the +12v rather than earth.

However, as soon as the engine cranks, the laptop loses comms still! Engine runs and purrs away, but comms gone.

Just about to try a different laptop and comms cable.

Will report back.

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