Can you have a sel code 12 on obd-1 that isn’t actually the initial diagnostic startup code

[A97obs]

I did the paper clip trick on the obd1 port and it went into the normal 1 1-2 blink diagnostics startup
Then after the 3 times with that it did
1 1-2 again 3 times continuously after the initial 3 times … I wasn’t sure but Can there be a real legit sel code 12 or am I just seeing the diagnostic setup repeating over and over for some specific reason .

This doesn’t pertain to a gmt400 but my 91 s10 which all the same obd1 methods of reading codes

 

[evilunclegrimace]

It is repeating.

 

[A97obs]

It is repeating.

So a 1 1-2 blink will just endless repeat in sequence if there are no sel codes

I was just worried that after the 3 times as they say I was seeing it more then that so I assumed maybe it was a code 12 going on

Ok case closed

 

[A97obs]

although few peeps on the gmt400 forum said “quote”

Actually, a '12' CAN be a code. If the SES lamp is on, and no other codes are in RMA, the '12' IS the stored error code. That means that during normal operation, reference pulses were missed when expected. If the SES is not on while running, and the only code displayed is '12" the problem may be different.

That's fairly consistent with the symptoms, too. Running for a period until warmed, complete ignition failure until cooled, then restart and running again until it's warmed.
The pickup coil and reluctor are suspect. The HEI switching module is suspect, and even the ignition coil is suspect.

 

[fancyTBI]

I’ve never heard that. I’ve always heard that 12 is normal operation and that there are no communication faults with the computer.

What post did you find that in?

 

[A97obs]

I’ve never heard that. I’ve always heard that 12 is normal operation and that there are no communication faults with the computer.

What post did you find that in?

A fella on the s10forum who’s fairly knowledgeable on early era Gm trucks
I frequent there often seeing as I own a 91 s-series pickup

 

[PlayingWithTBI]

I’ve always heard that 12 is normal operation and that there are no communication faults with the computer.

It does tell you that your ECM is communicating since you've a Malf Code for "No Distributor Reference" because the engine is turned on but not running. If you don't see that 12 with KOEO something's wrong with communications between the ECM and the SES light.

 

[A97obs]

It does tell you that your ECM is communicating since you've a Malf Code for "No Distributor Reference" because the engine is turned on but not running. If you don't see that 12 with KOEO something's wrong with communications between the ECM and the SES light.

Yes I do see the 1…….1..2 blink 3 times then it repeats that endlessly .
So I assumed maybe I am seeing a true code 12.
So your saying if I am seeing the duplicate 1.….1..2 blink after the first 3 sets then I have a No distributor refrence code ?

I probably am due for a New distributor drop in ..
I have all new plugs wire coil pack dist cap and rotor the only problem I find is the 4-6 second delay in the engine firing up and it’s not a hard start or erratic start or miss it’s just that delay before it fires up . It’s quite a few seconds longer then any engine should take to start .. but then again I assumed it’s maybe normal from sitting in cold garage through winter and only started once every 2-3 months .
This truck had no exhaust so I could never run it long . I welded up a new thrush and dumped it at the axle with that being said This today was the first long actual run time idle trucks had since I fixed the fuel pump in August … and when the rad leak hit today along with the SEL on I shut it down .. so the engine is experiencing its first back to life warm/Hot running idle in
6-8 years of not running. It’s got good pep good idle just the crank time is long and the SEL light came up after it got to operating temps. That’s right when the light came on and the radiator sprung the pin hole, which was not unexpected as old as the truck is .

 

[Schurkey]

Engine NOT running, the computer will blink Code 12 endlessly until you get sick of looking at it and yank the diagnostic paper-clip out of the diagnostic connector.



No reference pulses (Code 12) might be a failed pickup coil (engine won't run) or a failed ignition module (engine probably won't run) a failed wire harness between ignition module and computer (engine won't run right) or a failed computer (engine won't run right). So I suppose there could be a real, live Code 12 displayed...but the engine is going to be non-runable or running poorly which is more than likely going to be the complaint being chased, not the Code 12 which would seem entirely "normal".

I would expect that a Code 12 can not even be stored in the computer trouble-code memory. I think it's erased as soon as reference pulses are received again.

 

[evilunclegrimace]

although few peeps on the gmt400 forum said “quote”

Actually, a '12' CAN be a code. If the SES lamp is on, and no other codes are in RMA, the '12' IS the stored error code. That means that during normal operation, reference pulses were missed when expected. If the SES is not on while running, and the only code displayed is '12" the problem may be different.

That's fairly consistent with the symptoms, too. Running for a period until warmed, complete ignition failure until cooled, then restart and running again until it's warmed.
The pickup coil and reluctor are suspect. The HEI switching module is suspect, and even the ignition coil is the absense of a code 12 does indicateThe SES light is not supposed to be on with the engine running

although few peeps on the gmt400 forum said “quote”

Actually, a '12' CAN be a code. If the SES lamp is on, and no other codes are in RMA, the '12' IS the stored error code. That means that during normal operation, reference pulses were missed when expected. If the SES is not on while running, and the only code displayed is '12" the problem may be different.

That's fairly consistent with the symptoms, too. Running for a period until warmed, complete ignition failure until cooled, then restart and running again until it's warmed.
The pickup coil and reluctor are suspect. The HEI switching module is suspect, and even the ignition coil is suspect.

I can not find your senairo that in any of the diagnostic trouble shooting trees. No SES light while running and a code 12 indicates normal operation. If you have some thing to support your explanation please share it with the rest of us.