CEL Coming on and Turning Off

[drumnerd33]

Ok here is the proper procedure, find sti connector which is the yellow green wire by the 6 terminal block. Ground the sti connector then turn ignition to on position (without starting engine) read all codes, then reset codes by disconnect negative terminal on battery and press brake pedal for 5 to 10 seconds and reconnect negative terminal and check codes again. If cel flashes continuously prior to grounding sti then proceed to pinout test.

[Prafeston]

I've been out of town now since Wednesday night so the Festiva is sitting in a parking lot. I'll try to check the codes when I'm driving back home Sunday or Monday.

[bravekozak]

Which parking lot?

[XFSE71]

On most self test systems you are not supposed to have the engine running, only have ignition in the on position with engine not running. This may have been your problem though im not 100% on that because my festiva is not efi im just going by most cars that use the cel blink codes. Also the ecm should store every code it flashes even if the cel goes back off it will store them, all you should need to do is the self check in your driveway and it will display all stored codes.

our little OBDI ECAs do not remember running codes after the key has been turned off. the eca will store codes for hard faults (broken now). You should leave the engine running to pull short term memory of an intermittent flashing CEL while driving. if there are no codes at the time of self test, the CEL will just stare at you, until you figure it out, kinda like my 2nd ex...

[drumnerd33]

Re: CEL Coming on and Turning Off

Not true... That info was pulled from mitchell which is what all shops use, the ecm will hold stored codes you will risk the danger of ruining your ecm if you try while engine is running, that is why it's sparking... You are supposed to connect it and then turn key on with engine off.

Sent from my LG-LS970 using Tapatalk 2

[drumnerd33]

Re: CEL Coming on and Turning Off

Why would there be a computer memory clear procedure if it didn't hold memory of the codes? I learned this the hard way on my fox mustang I damaged my computer because I didn't follow the correct procedure. The whole point of being able to do a blink back test is that the computer will hold the faults and then you can do the test procedure to see what faults there is.

Sent from my LG-LS970 using Tapatalk 2

[XFSE71]

Not true... That info was pulled from mitchell which is what all shops use, the ecm will hold stored codes you will risk the danger of ruining your ecm if you try while engine is running, that is why it's sparking... You are supposed to connect it and then turn key on with engine off.

Sent from my LG-LS970 using Tapatalk 2

if it is sparking you have the wrong wire. blk single connector ... not clear or white ... not a T. If you are driving and your CEL flashes and you turn your key off the code will go away. So code 17 "lack of EGO switch" will not be stored for you to pull the next morning after the night before. You cannot hurt the ECA by grounding STI running or off. some shops actually use the factory manuals, not haynes/mitchell/chilton/all-data.

[drumnerd33]

I dont know which connector he was using but you have to ground the sti connector which will spark if you have the ignition in the on position. The ecm is designed to have a memory and store codes that were thrown while driving, this is how a obd1 system works, im not trying to argue with you im just trying to help.... my suggestion would be what does it hurt to try it the way mitchell is saying? every car i have ever had with an ecm is done this exact same way... if a computer see's a code and turns on the cel and then goes back off what good is it if it wouldnt store that thrown code? You would have to drive around and hope that same condition came up again??? All im saying is that the purpose of using the blink test is to see the stored codes and the ecm will store all codes even if only on for a little bit. Prafeston either way you want to try is fine i was just trying to give you the way a shop mechanic would do it because they have way more access to info then we do. My suggestion, try it the way mitchell says.

[XFSE71]

Why would there be a computer memory clear procedure if it didn't hold memory of the codes? I learned this the hard way on my fox mustang I damaged my computer because I didn't follow the correct procedure. The whole point of being able to do a blink back test is that the computer will hold the faults and then you can do the test procedure to see what faults there is.

Sent from my LG-LS970 using Tapatalk 2

hard faults, broken or unplugged will KOEO code to memory. KOER faults are not held in KAM in an early MECS System. Your Mustang is not MECS, it was EEC III never has been MECS, Festiva is. The "point" of blink codes was to satisfy BAR and the OBDI requirement. Codes? Codes? Your '65 Mustang didn't use no stinking codes. We don't need no codes!

[drumnerd33]

Re: CEL Coming on and Turning Off

65? Who said 65? I said fox body which is mid 80s to early 90s my mustang was a 91. Well like I said I'm not trying g to argue just trying to help so good luck.

Sent from my LG-LS970 using Tapatalk 2

[drumnerd33]

Re: CEL Coming on and Turning Off

Also not claiming to be an ecm expert by any means... Just giving you the directions on testing out of the professional manual. Sorry if I caused an argument.

Sent from my LG-LS970 using Tapatalk 2

[Prafeston]

I'll double check the connector I tried grounding last time. I'll make sure I have the right one this time and take pictures of what one I had tried.

[drumnerd33]

Re: CEL Coming on and Turning Off

Here is also a Haynes version of test procedure.

[XFSE71]

good luck with the Haynes manual. you don't need a VOM if you watch the light flash. You still will not see any KOER codes after shutting the engine off. just saying.

[Prafeston]

This is the wire I tried grounding a few days ago and was sparking from the ground side while the engine was running. Looks to be the right one. Single plug. Yellow w/ green line.