chevy47390

hello,
ground on the PCm uses four wires blk/wht on the wiring diagram
i d'nt know on what PCM points it's would be :
J1 60 J1 69 J1 21 J1 05 J1 is blue
J2 21 J2 50 J2 is clear.
there is six blk/wht wires, in reality.

PCM chassis is also at ground,

burhead1

Just a quick note on testing, I put the pic in as a example. The best was to test say power into a pcm would be to have one test lead on positive terminal of battery and other test lead on pin out of pcm set meter to vdc and you should get a reading of 0.1v or less if higher you have too much resistance or not enough voltage coming at the wire. Same thing for ground one lead on ground the other on the ground wire you are testing, This way works well it will show a problem where a ohms test will not.


C1 Connector at pcm pin 16,56,57,60 are grounds black/white
C1 Connector pin 19 pink power
C2 connector at pcm pin 24, pink power


Rather long video to show what I am talking about, but this is the best method of testing the part u want to watch is 3/4 of the way through. Although the whole video is good learning.

Jarvisw

Ah ok thanks guys. I get that part now.

I have to wait another night to get back to it, its literally freezing right now.

Jarvisw

Wow, that guy needs an editing program lol..

I couldn't check for drop as its not giving any voltage at all. What I did notice was the yellow/black wire (book and a PCM description online concur is the +12v for 24x sensor!) is currently grounded! The lt Green wire (Book, etc says is 24x ground) is ALSO ground..

I am going to check all the PCM grounds next, and will update results ASAP.

Jarvisw

Took the harnesses off the PCM and checked for ground. ALL the PCM/Ground wires had continuity.

The yel/blk wire thats SUPPOSED to carry the 12v for the 24x is NOT grounded unless the harness is connected to the PCM, then it is again.

Now, I had replaced the PCM, but is it possible I blew something out in BOTH of them??

chevy47390

you have an electrical test problem

the yel / blk wire brings +12 volts to CKP sensor

and yes, the CKP sensor shall submit a ground polarity on this wire ; this is normal.

according to the impedance of the CKP sensor, use a voltmeter or a small lamp (5 W) by connecting the + and - CKP to check supplied from the PCM.

the ground is LT grn wire

But it is not known expressly if CKP is supplied permanently.

it would be surprising and unlikely that the two PCM have the same problem

Jarvisw

Ok, I've tried that before but will again.

Also, let me try to explain the test again.

I tested the wires from the PCM harness and sensor DISCONNECTED. They both had full continuity end to end.

THEN I plugged the PCM harness back in but NOT the sensor, and the yel/blk wire was GROUNDED.. If it was supplying 12v, wouldn't that short out something?

And that was my main question about the 24x in the first place, "is it ALWAYS on or not?"

Anyway, I'll get back after checking for V at Y/B and Lt Green..

Oh, and I doubt both of them are blown, even tho they do the same thing. So it's got to be elsewhere... I hope!

Jarvisw

Ok, very strange..

I checked + to + and - to - on the yl/bk and lt green wires, unplugged from the sensor, and it gave me -10v!! I reversed the test leads and it came around to +10v.

Then I checked lt green to ground and same thing! -10v!

It also has 1k ohms across the 2 wires. If that matters.

chevy47390

And that was my main question about the 24x in the first place, "is it ALWAYS on or not?"

that is the question :
to-day, nobody knows the exact operation. it must be tested on a venture that works good.

I'm not shocked that there are residual polarity on wires ; PCM should not leave "in the air" the wires , permanently it analyzes each input to be able to analyze everything as default in operation; thus each wire is permanently connected to a high input system (or low) impedance.
and that is what you checked with your voltmeter.

have you the wiring PCM to test on my venture.
(160 points - function) not identified in Haynes book !

Jarvisw

GM Wiring Diagrams and Pinouts

The last link has a PDF With the pinouts for '01 and up.

Someone compiled it to convert 3.4s to Fiero's... um... huh?? lol

Thx for the help! really all you need to do is probe the yel/blk at the sensor with key on to find out.


Also, I think I'm going to start taking sensors off and checking with each one. Maybe another component is causing the PCM to malfunction.