I can't get into the diagnostic tests on my 95.

I've done it 100 times in the past, I did it a month ago.

I've been trying to find out whats wrong with my truck and in part of doing so I tried another computer (a9l mustang computer) and it didn't fix the problem. I put my computer back (a3m1, almost the same as a9l), and now my o2 sensor isn't reading the same, and now I can't get into diagnostic mode.

It's running a mustang computer, MAF conversion.

I've hooked it up right, and I've done a continuity test between the 60 pin connector and the test connector and I have continuity.

Basically, I hook it up and turn the key, nothing happens. I do it by running a jumper wire from the pos to the STO wire with a test light inbetween (light comes on indicating 12v), and a jumper between the STI and the upper right terminal in the diagnostic connector. All 3 have continuity to the 60 pin computer connector.

I've done it this way in the past and it's been fine...but all of a sudden I can't get it to work.

I don't seem to have any bad wires, and I'm connecting it correctly, wth is going on here??

 

Do you have access to a Standard F150 computer just to test the test setup? Do the pins for DTC go to the same pins at the computer for truck and mustang?
What year mustang was the computer for?
I have pinouts in 95 Emissions manual for a lot of models if you have specific questions.
Just some thoughts.

 

Sounds like a wire came loose in the plug for the PCM or a pin got messed up.

You may need to put a breakout box on it to find it.

 

Try jumping the clutch interlock switch to signal return. I can't remember pin numbers off the top of my head, but I'm thinking pin 14. I couldn't get the computer to go into self test with my mass air swap either until I jumped this wire. Also try holding the clutch pedal to the floor, but I'm not sure that will work (I think the V8 manual trucks didn't complete the circuit to signal return, but could be that yours is connected).

 

If you are talking about 5.8L 1995 California PCM pin numbers, #14 is injector #8 and the 12V from the clutch pedal position switch is pin #30.

You may be right if you are using an older EEC, I do not know about the conversion .

 

it's been a while since I did this I guess......thanks for the correct info.

 

I have performed the diagnostic test with this computer in this truck exactly how it is. I do need to have the clutch in for the KOER test, but not the KOEO. The KOEO will just spit a clutch code at me if I don't.

I cannot easily install a SD computer, all I'd really be able to do is try the a9l again.

I guess it's possible a pin got screwed up...but kind of unlikely if that's the case.

 

sometimes the pins get dust on them and do not work correctly.

try opening the connector and blow it out.

this has me scratching my head.

 

Any chance your test light is bad? When you jump the normal leads in the DTC will the Check Engine light do anything? I rigged up a switch and can turn the switch off and on from cab while the DTC is jumped out and can start and stop and watch the CEL thru the cycles.

 

The test light works fine, and when it's connected the CEL aluminates slightly, just like it did before.

I've got the A9L back again, I'll put that in and check the computer pins.

 

So I took my computer connector apart and found that the HEGO gnd pin was damaged along with the pin next to it, I think they're pins 29 and 30.

I decided to take the 60pin connector from my junk truck and install it, so I switched all the wiring over to a new connector, plugged it in, and the o2 sensor is now working again.

I quickly tried the diagnostic test, and it didn't work. I took it out for a test drive and it runs much better now that the o2 sensor is back.

I've tried the diagnostic test with either the a9l or a3m1 computers I have and neither of them are going into test mode.

I did a continuity test on the STO, STI, and SIG RTN wires at the diagnostic plug with the pins going to the computer - and had continuity on all 3. So it seems that those wires are connected to the pins on the computer - so I have NOOO idea why this isn't working....

 

FOUND IT...

Wanna know what it was?

My stinking jumper wire between the STI and SIG RTN wasn't making contact!!

I found it because I took two little male connectors I have and shoved them into the plug terminals so I'd have something to clip my jumpers to - and I decided to try using the jumper clip to hold the two terminals together - and it worked!

I tested my jumper and found that the jumper is no good!

How about that!

 

you had to be a trip to be around since this started.

going over and over it in your mind what it could be.

i am glad you solved it.

why is it always something so simple?

 

It's the same jumper I've used for previous tests too....oh well.

 

It's so easy to say my test equip is great, but we do have to start looking for the simple things at times - glad you found it. Sometimes it's even embarassing to admit what we've done wrong or let catch us when we're not looking, ain't it?
We've all been there, if we do anything at all.