Fast Blinking CEL - Cruise light not on

Finished replacing my battery and shortly after I got a fast blinking CEL and the cruise light was off (like normal) - Last time I tripped a CEL I think I get a steady CEL with a blinking cruise light

Did a LV and there is no code coming up so I did not reset the ECU.

Turned off the car after LV - restarted - No CEL.

Tried searching - couldn't find anything. Any thoughts?

Car is running normal (although I have not gone WOT) only think I changed was the battery.

Did a few WOT runs - car is running perfect, no CEL since reset.

Blinking CEL, no CC usually = misfire in one or more cylinders. If sustained/detected for a certain period of time will set a permanent code.

You can check Pending Codes for which cylinder was the culprit.

Thanks...LV is not reading any pending or memorized codes. Logged runs look normal.

I was surprised the cel went away after shutting down and restarting.

The blinking light is back for the 2nd time - I have been logging roughness on all cylinders for all my driving and there are literally 0 counts while driving and a maybe one or 2 during warmup (I have always had these). WOT logs look perfect.

Today when I first turned the key it sounded "funny" I think I heard a click and the radiator fans kicked on before I cranked it to start. Once it started I got the blinking CEL only (no cruise blinking). Did a LV and again no code found...my fuel trims look normal - no learned knock. Turned off the car and restarted - CEL gone.

I am starting to think my new battery is the cause of this nonsense. I looked at my new battery and it is the same Optima Yellow top DR51, I had previously but the the model/serial numbers are different. Could the battery be the cause of this phantom CEL? I mean - it has 450 cold cranking Amps (about the same as my previous model battery). I am not sure why it would matter.

check your green connectors, just in case. probably not in because lv would show codes if the connectors were connected, but still worth a look.

Thanks - yeah I checked the connectors - all good.

More info...

I turn the ignition to the on position and the fans are cycling as if in test mode.. IAM is at 0, even tho knock is non existent on my logs. What is weird is that it is completely random. The CEL only goes on if the fan cycles at startup. If the car starts without a cel it does not come on unless I turn off the car and restart.

Starting to think it is an ecu issue...my car was on the tsb list for a new relay and/or Ecu and I never took it in. But the tsb thread mentions nothing about a CEL.

Did a little more research - looks like the ecu is randomly going into test mode (fast blinking Cel and cycling fans). No clue what to do.

Any know how/where I can get a new ecu?

I have never needed to test it but by connecting the green test connectors does it ground out the circuit? If so you could have worn the insulation down somewhere close to them and sometimes its grouding out on startup?

Just an idea to look at, ive seen some cars that the test connector itself had frayed at the connector and wasnt even making contact because of so much use.

Hope you dont need an ecu.

Dave

Thanks...I will take a closer look. I suspect my new battery may have caused some kind of surge. It all started the day I installed a new battery.

I've seen it a couple of times usually is some sort of grounding issue. Try PMing Mike he may be able to give you a more in dept answer.

If it's a ground issue. clening them may be all you need. There is one on the dog bone bracket on the firewall, one on the bottom of the drivers side head, the one on the battery.

FWIW, I have learned to wire brush all mating surfaces such as tranny to block, starter to tranny, tranny to cross member, etc.

Thanks guys...I will check the grounds.

I am still getting a random cel at startup (and only at start up). If I get the CEL at startup and turn off the car, wiggle the tactrix connection (which I always have plugged in) and then restart - CEL magically goes away. None of the CELs have ever had an associated code.

I checked and cleaned grounds also removed lower dash to check all cabling under the dash where the tactrix cable plugs in.. I tried to cause the cel by repeatedly starting and turning off the car while fiddling with the cables leading to where the tactrix plugs in, I found nothing out of the ordinary and was not able to trip a CEL.

I put everything back together and 2 starts later - CEL. Wondering if keeping the tactrix 2.0 plugged in all the time is the cause?

Any other suggestions on where to look?