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Discussion Starter · #1 ·
I am trying to understand what
Distr ref low (black with pink) wire should read on meter.

I am reading with key on .09v and with key on car running .03v

The red wire (ignition feed)
Is showing battery voltage which is correct.

The high and low resolution wires look good and during rev up tighten up smoothly these are (purple with white) and (red with black)

I am chasing a intake back fire and want to rule out completely opti

See pics below






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I am trying to understand what
Distr ref low (black with pink) wire should read on meter.
In the FSM the PCM is labeled reference low distributor ground.
Short version all opti signals are relative to this (reference) ground the PCM uses. Power is also supplied by the PCM.

You might get more information by scoping the input to the coil. It will show if the PCM and ICM are outputing a good signal and may show a bad distributor, plug, or plug wire.
 

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Discussion Starter · #3 · (Edited)
Thank you for helping me out

If I am understanding you correctly I believe you are saying to scope the white wire from pcm to icm
Which is B

And also scope connector D
ICM to IC

C is a ground
A is power

Distributor cap and rotor are new
So are plugs and wires

Ac delco brand

Just trying to check off my list that area is not my problem.




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At ICM
A (pink) 12VPositive
D Will be 12VNegative signal that pulses the coil.
OR
At coil plug:
A (pink) 12VPositive
B Will be 12VNegative signal that pulses the coil.

Goldwagon's diagrams show D/B being a WHT/BLK wire. Your diagram shows 1996/97 so not a b body?

With no other connection to the car (power or other scope lead) you can use probe tip to A and shield(ground) to D.Scope must have it's own power(battery).
Any other connections when scoping the coil this way could cause damage.

The better way is tip to D and shield(ground) to battery minus(or body ground). The waveform will be upside down. D will always be +12V except when coil is triggered then it goes to 0V(negative) You will have to change the way the scope triggers.

Have a look at this PDF:

Down load all at:

What scope is that?
 

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Discussion Starter · #5 ·
I think you are right about diagram I was just posting a random lt1 image from google.
I did just print your link off so thank you for that.

I will give this a try with the scope like you suggested..

"The better way is tip to D and shield(ground) to battery minus(or body ground). The waveform will be upside down. D will always be +12V except when coil is triggered then it goes to 0V(negative) You will have to change the way the scope triggers."

so to confirm what you are saying I will scope probe ICM. D and scope probe ground to battery negative.

Ps. this is what I am trying to correct.


the scope I am using is the AESWave U-scope.

Super basic but its helpful
 
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