av81

I have a solid check engine light after doing some work (of course ) I tried to connect my old snap on brick using multi 1 connection all I get is the dreaded "can not communicate " , any other way of checking codes? Maybe a jumper to get the light flashing ?
this is sour everything is where it should be as far as connections only thing different I replaced the distributor with a Rock auto Spectrum and I am noticing the timing doesn't advance when I plug the four wire connector back in , but if the ecm is seeing something wrong maybe no advance ? Any Ideas ?

av81

I guess I could jump the first two terminals to get the light to flash , I guess the real question can I get the scanner to read data? The software is in the brick .

Big2Bird

Sorry. I had the same thing happen. I borrowed TimAT's Red Box, and it went nutz.
Plugged in my OTC unit, no issues.
Snap On did not make that cartridge correctly, or were both nutz.

I should add I have 4 ECM's with 3 different chips. (For off-roading purposes only).

terry82

I don't know about the rock auto distributer.Is it a factory type replacement for the old factory distributer.If so it may not be comunicating with the computer.un plug the the four plug line and see if light goes out.I have replaced the distributer on 1981 vettes with a old style distributer with no 4 plug in and did not get a light.

Antz81

If the computer system was still running. Then you should have got a light when you did that.

It's best to disconnect the battery for about 30s and then go for a short drive to clear any stored codes before trying to read them

To read the codes without a reader short the two pins under the ash tray closest to there drivers side with the ignition on (engine off) it will start with 12 (one flash, short pause, two flashes, long pause) this will be repeated two more to.es before it moves to the next code. Once it has gone trough all the codes it will start again.

av81

Thanks gents , I figured out how to get the snap on scanner to read , looking at the snapon instructions to connect ,the diagram picture is upside down so when you hook it up backwards it works ,
So the scanner data does not show tach or dwell (zero reading) , the only code is 12 but with flashing diagnostics I get a 23 after 12 ,
Going to have a look at the new distributor today.

Antz81

23 is a mix control solenoid fault. Since the scanner doesn't show it could have happened any time in the past 50 starts.
12 is no distributor reference pulse. So could be your issue since the scanner won't read rpm or dwell. (Code 12 is normally ignored since it will always show up)

av81

found the problem , the flashing code 23 is just a ghost and does not appear on the scanner just 12 , it ended up being the quality new distributor the four wire harness that plugs into the module has an open so no tach signal was getting to the ecm , I swapped out the old harness now I have advance when I plug the connector back in and a tach and dwell reading on the scanner no check engine light... if anything positive came from this problem 1 ,dont buy cheap Rock auto parts 2, I got reacquainted with diagnostics with this old school technology ... the flashing light method really didnt help , I would have been a parts changer if I didnt have a scanner.