CEL

1994gt · Oct 25, 2015

This has me puzzled. I had an exhaust leak with no CEL. Today I replaced the gaskets with the reflex ones and the leak is gone. I reconnected everything I took off and double checked I did. Now, when the car is idling, it's still fine. Then I drive it, and after 1-2 minutes of driving, the cel comes on. I can shut the car off and restart it and the light is off But then comes right back on after about driving 1-2 minutes again. Car runs perfect and runs strong. No drive ability issues. I did disconnect the o2 sensors to drop the X pipe but I reconnected them back up. Tried checking codes using the jumper wire with both engine off and engine running. Didn't get any codes at all. Not sure where to go from here. Want to get some input before I go any further.

ranger56528 · Oct 25, 2015

Have you disconnected the battery and let it sit for 15 min or so,then reconnect them and start it,I have even read where when both battery cables disconnected you touch neg and pos cables and that is supposed to also help clear the ecu. When I changed my exhaust and a few other things my light came on and I just let it sit with the battery disconnected and no more cel.

CC'S95GT · Oct 26, 2015

Where did you put the jumper wire to read codes. Follow the instructions in the Haynes/Chilton manual for KOEO and KOER codes
You should have at least gotten 111 whether any codes are present or not.

1994gt · Oct 26, 2015

I have not tried to disconnect the battery. And I connected the jumper cable like it shows on many sites on the Internet and YouTube.

CC'S95GT · Oct 26, 2015

1994gt said:
I have not tried to disconnect the battery. And I connected the jumper cable like it shows on many sites on the Internet and YouTube.

Just making sure.
You don't know how many people say they can't pull codes on their 94/95GT, and it because they're trying to use the OBD2 port under the dash.
With the pins jumpered, did the CEL in the car flash or flicker at all?

ranger56528 · Oct 26, 2015

I bought a cheep OBD1 tester for 25 bucks and just plug it in....plug under hood behind passenger strut/shock tower and make sure you plug both in,big plug and single plug.

ranger56528 · Oct 26, 2015

Unplug negative side of battery for 1/2 hour hook up start and see what happens,easiest thing to do 1st.

1994gt · Oct 26, 2015

I left the battery unhooked for a couple hours and it didn't fix my problem. Went to the parts store and bought the obd1 scan tool for $30. When i got home th code was on so I left the car running and connected the scan tool. Gave me a 314 and a 311. 314 is bank 2 oxygen sensor according to the book and the 311 is a thermactor no operation code. Which side it bank 2?

1994gt · Oct 26, 2015

So after doing some research, it looks like the 311,314 codes are for the smog pump?? Mine is long gone but has been that way for well over a year with no light. I also read that these 2 codes by themselves won't set off the light. Is that true? Not sure why the light decided to come on now after the pump has been gone for this long.

5.0l cory · Oct 26, 2015

my smog pump has been gone for 3yrs no light but my 02 sensors r shot check engine lights comes on for them and I think the codes where 171 & 172. and I just replaced both 02 sensors I hope I helped u out .

ranger56528 · Oct 26, 2015

Ya smog doesn't matter mines gone to,I get codes from it but no cel,I believe bank two is driver side but could be wrong.

ranger56528 · Oct 26, 2015

I just replaced both o2 sensors too when I did my whole exhaust,went with cat backs plus I bought a new o2 harness being the stock one is beat up.

ranger56528 · Oct 26, 2015

I would add that when I did exhaust and o2 sensors my cel came on and I disconnected the neg side for 20 min or so and it has not come on since.

1994gt · Oct 27, 2015

I don't think the o2 sensors have been replaced to my knowledge. Should I go ahead and replace both sensors?

ranger56528 · Oct 27, 2015

That's up to you,if they are 20 year old O2 sensors ya it's time if ya have the funds just part of a tune up in my book.

1994gt · Nov 1, 2015

I did the KOEO test today and got a 564 code. This was the only code. It states it's a fan issue. When I ran the test, I did hear relays click the. The fan turned on low speed then it hit high speed but only for a second. Then the test light flickered then spit out the 564 code. Any idea of where to begin on this one?

ranger56528 · Nov 1, 2015

Un hook battery to clear codes and redo the scan if it still comes up check your grounds and if that fails check your constant control relay module. (CCRM)...that's what I've read...

1994gt · Nov 1, 2015

What's the ccrm and where is that located?

CC'S95GT · Nov 2, 2015

You do not have to disconnect the battery to clear the codes. Read the book.
CCRM= Constant Control Realy Module. It's located next to the coolant overflow tank. It has relays for fuel pump, A/c compressor, hi and low speed rad fan, and ecm.
The hi speed fan should be on anytume the a/c is on. You can also force it on by disconnecting the coolant temp sensor. (there are 2 and only 1 will turn the fan on.
It's not uncommon for the fan motor to fail.