unable to pull codes - new FR harness

stangman16 · Oct 18, 2009

Bought a new harness for my A9L EFI conversion due to all the issues with the used harness I had. But now i'm unable to pull any codes, and I double checked everything before firing the engine. The engine started right away and when I tried to do a KOER test I could hear the engine rev up to ~1500 as normal but I never got any codes from my reader - it just displayed 000. Tried to do a KOEO test and I didn't hear the computer click like it usually does, and no codes - 000.

Found JRichkers instructions and tested the resistance between the computer test ground (gray/red) and the battery ground. 4.43 ohms

Tested resistance between pin 46 and the STI connector and my Fluke voltmeter reads OL. (open loop)

Tested resistance of pin 46 on ECM and pins 40/60 on ECM. Both read 0.2 ohms.

Since the voltmeter is reading OL it seems I have a wiring problem, but I'm not sure where it would be, especially since I have a new O2 and FR main harness. I have a ground to firewall and a battery cable for a ground between the block and chasis. Black/white EEC battery ground (26) wire is connected, and the body ground wire (38) is connected inside by the glove box on my '66.

Here's the harness diagram, I do not see how the wiring could be messed up, but if it is - would it be within the green area on this diagram? Any ideas?

Red X's indicate not used, and I have not removed or touched that part of wiring. #37 is for AC clutch connector and the others are TAB/TAD, EGR, and AC pressure switch.

liljoe07 · Oct 18, 2009

STI and 46 will show an open line. Different circuit.

What you need to ohm out is PIN 46 at the ECM to the SIGRTN at the VIP connector shown below.
If good.....

Then you need to test the STI to a ground for 5v.
If good.........

The you need to Ohm out the STO to PIN 17 at the ECM

View attachment 242106

stangman16 · Oct 18, 2009

Thank you for the info, here's the results:

Pin 46 to Sigrtn = 0.6 ohms
STI to ground (used battery) = 5.5v key on, 0 off
STO to Pin 17 = 0.3 ohms

So all wiring is okay?

liljoe07 · Oct 18, 2009

Yes wiring checks out.

leave the scanner alone for now.

Using the same diagram above. Make a jumper(paper clip, small wire) and go from the STI to the SIGRTN. Go sit in the driver seat and turn the Key on to run a KOEO test. See if the Check Engine light flashes codes.

stangman16 · Oct 18, 2009

No check engine light and I can't seem to find my test light. Hooked up a DVM and I'm getting 0.20v constant, maybe not when I turn the key - not sure, i'm not quick enough lol. Key off it shows 12v

liljoe07 · Oct 18, 2009

12v where?

stangman16 · Oct 18, 2009

between STO and battery + with the key off shows 12v, key on it shows 0.20v (didn't have a test light so I used my digital multi-meter)

liljoe07 · Oct 18, 2009

Try this, just ground the STI to a body ground. Then hook up the volt meter( I can never find my test light either....never) like normal. And try the KOEO codes.

stangman16 · Oct 19, 2009

When i turn the key it goes to 0.6, then down to 0.22 and staying about 0.22-0.24 constant. It does not go to 0 to where i can tell if it is throwing a code

stangman16 · Oct 19, 2009

okay perhaps there is a wiring issue with the CEL, so I picked up a light from radio shack to use for the check engine light.

when I turn the key it does not come on. If i disconnect the side of the light that goes to the 'pink/lt green wire and touch it to the body it lights up. The other side is coming from my 'crank & run' power source. My ECM has been throwing a code 15 because of my quarterhorse...so it should light up always - unfortunately.

The book states: Pink/Light Green wire connect to check engine light. Connect other side of the light to a "Crank" and "Run" power source. This must be used.

I can only assume the Pink/Light Green wire is a ground coming from the computer and it closes the loop when there is an error code..?

If i have this wired correctly, then what do I test next to find out why the Pink/Light Green wire does close the loop?

liljoe07 · Oct 19, 2009

You may need to pull the QH out and try again.

Did you go from the STI straight to a ground? Then try the KOEO test?

stangman16 · Oct 19, 2009

STI striaght to ground. Checked again .6v, removed quarterhorse, checked again and still showing .6v with the key in the "Run" position, key off = 12v still.

liljoe07 · Oct 19, 2009

Sheesh.....

What did the O2 harness come from?

stangman16 · Oct 19, 2009

ebay for 89-93 with long-tube headers

Details:
--------
Mustang O2 Oxygen sensor harness 24" ext built in 87-93

This New harness has 24" of wire already added for long tube Headers. It connects the two oxygen sensors and oil level sensor into the main harness. Fits Ford Mustangs 5.0L 1987-1993 with manual transmission.

---------------------------

It plugged right in to main connector and both O2's for a 93 mustang.

strtrcr50 · Oct 19, 2009

Wonder if the o2 harness is pinned for an automatic computer(A9P)?

liljoe07 · Oct 19, 2009

Try unplugging the 02 harness and Run the KOEO test.

stangman16 · Oct 20, 2009

Disconnected O2 harness and tried the KOEO test... same thing, but it reads .5v constant. I can hear the relay click still..

liljoe07 · Oct 20, 2009

Something has to be wrong with the ECM.

But first stick the volt meter red lead in the SIGRTN wire at the code test connector. Black lead to a good body ground. Turn key on and see of any voltage shows up.

Monitor that voltage while cranking also.

liljoe07 · Oct 20, 2009

stangman16 said:
Thank you for the info, here's the results:

Pin 46 to Sigrtn = 0.6 ohms
STI to ground (used battery) = 5.5v key on, 0 off
STO to Pin 17 = 0.3 ohms

So all wiring is okay?

Where these checks done with the ECM unhooked? Not talking about the STI to ground test. Just the other 2

stangman16 · Oct 20, 2009

liljoe07 said:
Where these checks done with the ECM unhooked? Not talking about the STI to ground test. Just the other 2

Yeah - ECM was disconnected and I probed from the 60-pin connector.. Just today I read that you're not supposed to do that..

liljoe07 said:
But first stick the volt meter red lead in the SIGRTN wire at the code test connector. Black lead to a good body ground. Turn key on and see of any voltage shows up.

Monitor that voltage while cranking also.

Let me check this, ty

unable to pull codes - new FR harness

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