I'm attempting to read the codes on my '94 but I'm not sure what the readouts mean. This is in relation to the problem I'll describe below.

I'm using a paper clip that inserted into the #4 and #12 pins. The only readings I get occur on the digital display. Service light does not flash, but stays on.

Read outs:

The number "1" shows followed by "C 12" above it.
The "C 12" disappears and the number "1" stays.
"3 dashed lines" appear above the number "1" and hold for 2 seconds, while the number "1" is still displayed. These appear where is said "C 12"
Dashed lines and number disappear.
The number "4" appears (where the number "1' was)
"3 dashed lines" appear above for 2 seconds
The number "9" appears
"3 dashed lines" appear
The letter "A" appears
"3 dashed lines" appear
The number "1" appears and hold sindefinately.



What happens is that on cold starts, almost always, when you press on the gas to accelerate the car will stutter/sputter, and the car will excellerate extremely slow. Even if I mash the gas it does not improve. This will happen till the car gets to say 60mph. This is noticeably worse on extremely cold days, even when I let the oil temp. come up. However, this will happen regardless of oil temperature, but almost always happens if the car has been setting for several hours.

Also, the cruise control doesn't always stay on. I find brake fluid around the cap of the reservoir. Could there be a vacuume issue? I may just need a new cap for the reservoir.

I had plugs, plugs wire, and ignition wires replaced but this still occurs.

 

C12 indicates that the Diagnostics are functioning properly and no codes are stored.

The 1,4, 9, and A are for subsections of the diagnostic system.

If I remember right...

1 = CCM
4 = PCM/ECM
9 = ASR/ABS
A = DERM

As for your problem, I wonder if I sensor has a loose connection. If that were the case though, I'd think you would have a code for it. Does the car run smoothly most of the time? I wonder if maybe a plug wire is swapped somewhere maybe?

If the cruise is acting up, possibly is could be a vacuum issue. On my '86, the cruise quit and I found that the vacuum hoses were routed under the battery tray and battery acid had seeped down and ruined the hose. The hoses on my '94 now appear to run along side, but not below, the battery. It's worth a shot anyway. Hope some of this helps.

 

The car does run smoothly most of the time. This also occurs if I am very low on fuel, on reserve.

Thing is, I don't want to dump a bunch of money into parts it doesn't need. I could replace the opti, which some people think the problem is, but since there are no codes, I don't want go that route just yet.

 

Well this is going to sound insanely stupid but ... why don't you just try always keeping the tank at least half full

 

Does it *also* occur when you're low on fuel, or *only* when you're low on fuel? You really shouldn't let it run on reserve or get that low often, because the fuel pump could potentially burn up without gas covering it all the time. Granted, they're easy to replace on a Vette, but that still doesn't mean you want to spend the money if you don't have to.

 

Do have a 12 or 16 pin connector? I have a 94 and it has a 16 pin connector that I need a code reader for, can't use a paper clip on them. It's still obd1. Just curious.

 

Actualy you can use a paper clip on the 94 and 95. The clip goes between pins 4 and 12 on the 16 pin connector.

 

Your right it does sound stupid because it's a stupid comment.

I guess no one on here has ever run a car to near empty.

 

It "also" occurs when low on fuel. I don't exclusively run it on reserve, but the few times it did get that low that problem would occur. This is why I think maybe it's a fuel problem. It could be the pump, a clogged injector, a clog in a line either from the tank or back to the tank. Hard to tell I guess, but I'm no mechanic and someone else will be doing the work, so I need to be as informed as possible before I let someone go to work on the car.

 

I tried it out and it didn't work. If memory serves me right #12 on the 16 pin is empty, no wire going to it. The fsm says you can only do it on a 12 pin so I wasn't about to go poking around with a paper clip trying to get it to work. I would go check to be sure but we got freezing rain last night and my car cover is frozen, not comin' off till it thaws.

 

1, 7, 10, 11, 13, 15 are empty on my car.

 

Yeah, you're probably right, relying on memory isn't always the best. I just wish I could go check so it doesn't sit here and knaw at me.

If you're not getting any codes it is most likely mechanical. If you know it's not spark, then check fuel pressure. You can pick up a gauge at any autoparts store.

 

Your statment is confusing, first you state "I tried it out and it didn't work" then you state you "The fsm says you can only do it on a 12 pin so I wasn't about to go poking around with a paper clip trying to get it to work". I asure you it does work and there have been many post about this and I have done it many times. I have the Helms service manual and if you look at page 8D-7 you will see that pin 12 is CCM Dignostic enable and pin 4 is ground. Also check sheet 8D-4, it states "to enter diagnostic mode, ground terninal "12" of the DLC Here is the pinout looking at the DLC or "ALDL" conector and a paper clip between 4 and 12 will work.


01 02 03 04 05 06 07 08
09 10 11 12 13 14 15 16

 

I was only going by what I found on page 6E-6. It only talks about checking codes if you have 12 pin. They make it sound as if you can't check codes if you have 16 pin. My fault for not checking the other book and looking for the info in another place. I haven't had the books that long and I'm still thumbing through them when I can. I'm also much more familar with Chysler, this is my first gm with efi. I still have tons to learn, thanks for the info.

I did try to jump 4-12, but after it didn't work for me I wasn't about to experiment. I'll try it again when it gets a little warmer out.