Cobra ECU PCM Test Procedure?

lucheski

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So I found the short. Zero Ohms resistance to ground at the power input at the power distribution block
Removed checked battery Power wire OK - no shorts in battery cable
Removed check Alternator power wire OK - no shorts in alternator or wire
removed checked starter power wire OK - No shorts in starter wire or the starter itself


Tested again power distribution block positive terminal with no wires connected and got ZERO Ohms of resistance to ground!!
 
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lucheski

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Having a Fuse in F1.6 is causing the short. C133 is disconnected, Also the PCM is disconnected

How I found it
removing fuses F1.1 - F1.12 removed short.....so I went adding fuse 1 by 1 tro see which circuit returned the short....Add the fuse F1.6 returns the short....removing Fuse f1.6 removes short...

- - - Updated - - -

03MustangBJB_zps6k34wkbi.jpg
 

lucheski

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you have a short.

fuse 2 and 8. inside car

engine controls

the big engine harness connector with 10 mm bolt.

unplug connector

install new fuse in f26

turn key and see if fuse blows again.



what you are doing is isolating the short.

most of the time it’s on engine a component is shorting.

there was a thread about a month ago in tech section about pcm fuse blowing.

What is the name of the thread?
 

lucheski

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At the end of it all there was no short. Far as I can see it was just the blown #6 fuse after all. When the first replacement fuse ( not new fuse this one was at least 15 years old) blew after a couple minutes running the car. I freaked out assuming a short or water damage and I have tested nearly every wire and circuit, switch and relay in the car and can find nothing wrong. No shorts, opens, water damage, or corrosion. Tonight I did numerous parasitic draw tests and measured only 2 mili amps of draw. So tonight I put in another used 10 yr old fuse I had lying around and car is running fine. My test going from the positive terminal distribution box to the engine block was wrong. Electrically the positive post of the power distribution box is the same positive terminal of the battery. I measured from there to engine block and got 0 ohms of resistance while the battery is connected. Which would be same as testing resistance between positive and negative terminals of the battery. Which was a incorrect test. No short was found. Car is running now with replacement fuse.
 
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