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Discussion Starter #1
OK, I have probed all wires from the pump harness to the ECM and all are OK. Book says I should have a 60hz single at the ECM while running at 900 rpm. So my question is the optical sensor supplying the 60hz signal or is the ECM? I think it must be the ECM because I know for a fact the optical sensor is OK. Can anyone enlighten me?

Thanks
Greg
 

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There are 88pins on the PCM - any particular pin you're concerned with?
 

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Discussion Starter #3
I would have to go look for sure but I believe PD15. The pin is from the optical sensor and is suppose to read 60hz at 900rpm. I just put a scope on it and is only a 25 millivolt signal.

Greg
 

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Folks, he's working on a '94 or '95 OBD1 vehicle, but this applies to OBD2, as well.

Ok - pull the OS connector, Ign on, look for +5v on pin A, with D as common, post the actual voltage read on B and C

Reconnect, check for +5v on A, post voltage you read on B and C

We're looking for static open-circuit vs connected or closed-circuit voltages

Be sure to use pin D as dvm or scope common
 

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Greg, did you ever do the optical sensor change out you were contemplating?
 

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Yes, it didn't help, nor did the serviceable driver that I sent with it, I had an extra laying around, unfortunately I don't have an extra PCM that will work for him
 

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Discussion Starter #7
I'll check it out tomorrow.

Greg

gmctd;1587153; said:
Folks, he's working on a '94 or '95 OBD1 vehicle, but this applies to OBD2, as well.

Ok - pull the OS connector, Ign on, look for +5v on pin A, with D as common, post the actual voltage read on B and C

Reconnect, check for +5v on A, post voltage you read on B and C

We're looking for static open-circuit vs connected or closed-circuit voltages

Be sure to use pin D as dvm or scope common
 

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Discussion Starter #8
OK this is what we have.

OS Unhooked is
A=5v
B=12v
C=5v

OC Hooked Up
A=5v
B=12v
C=4.9v

I only have a 25mv signal from PD15 when running 900 rpm and at a 50 nanosec rate which puts it up around 20mhz instead of 60hz.

Greg
 

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That can't be good - what do you see on PD9, level and freq?

Optic Sensor is generating the x64 hi-res and x8 lo-res signal

900rpm x 4ce = 3600 ce / 60 sec = 60ce\sec = 1ce\.016ms

Hi-res is 64 x 60ce = 3840hz = 1\260usec
 

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Discussion Starter #10 (Edited)
OK PD9 was 4.7v at 125 micro sec. I have a dmv with freq and it was about 3.4khz but nothing out of PD15. So according to the book the OC is bad? But this pump was ran on the test stand before Mike sent it to me.

Greg
 

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47v or 4.7v ?

You're using the original OS filter?

Indications are bad connections, maybe grounding, or PCM is bad.
 

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Discussion Starter #12
It had to be 4.7, I think I read the scale wrong. Since the OC has a 5v ref I would think the OC would be putting out the signal, not the ECM? Anyway I will go over all the wiring again but it has all checked out OK. I wish I had a spare ECM, I hate to buy one and that not be the problem.

Greg
 

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What about the filter?
 
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