Oh no, My check light came on!

[jaketime81]

My check light came on two days ago and I cant figure out why. I tried to check the code by holding down the odometer button while turning the ignition, and it runs through the code check, and moves gages back and forth, but doesnt say any codes. The light turned off this morning, but came back on about 8 hours later. I have checked the gas cap, couild it have anything to do with my cracked exaust manifold? Any suggestions is appritiated, thanks -jake

[MudderChuck]

I´ve seen intermitant codes/light before, it always turned out to be the 02 sensor (always is a strong word, as soon as you use it, your usually proved wrong).
The cracked exhaust manifold, could be messing with the output values.
Most intermitant, 02 sensor check engine lights, have come on first at highway speeds for me. The computer didn´t save the trouble code either.
I also had a wire that flopped over on the exhaust manifold, that caused intermitant, trouble codes/lights for the 02 sensor.

[Bounty__Hunter]

If your guage cluster runs through it's test cycle, you released the odometer button too soon. Hold it down until after you turn the key off. Try it again and let us know.

[L33TJ33P]

Mine just did that. Watch your Temp durring normal operation. Is the Temp lower than usual?

Mine was a Thermostat that was stuck open.

[jaketime81]

Ill try to check the code again when the check engine light comes back on. It seems to come on after ive been driving for a while and the engines warmed up. After it cools of the light goes off.
The light did first come on while driving on the freeway, my gas mileage has been getting worse lately 10-12 mpg compared to around 15, when i got it, a year ago. could it be the 02 sensor? is it hard/expensive to replace?
My temp has been staying at a normal level.

[L33TJ33P]

The Techs let me know that if you check your own codes it will erase anything that they can get. it takes a couple driving cycles to get the code back. Thermostat problems will apparently not show up with your Dashboard check.

Also, Just because your code reader says "O2" problem doesn't always mean it is the O2 Sensor. It can be that the O2 sensor is reading higher than normal O2 but it can be caused by thinks such as the Engine burning more fuel to try and force the Engine to run at otimal temps for fuel effeciancy. My mpg went down due to the computer sending more fuel to try and heat the engine to optimal temp but, with the therm stuck open it just couldn't warm up to the norm.

I am not saying that a therm is your problem, I am saying to drive it around a couple days then have a stealership read the codes for you, if possible.

[Bounty__Hunter]

I don't believe that checking your own codes will erase anything useful to a tech. Take anything the stealership tells you with a grain of salt

[L33TJ33P]

Well, it Does. At least it did,on the TJ. there's your grain of salt.

::: Edit :::
Also, When checking the TJ codes the Guages will test themselves.

Hold the Odometer turn the key to on.
you will here a Beep and then it will show a single string of numbers. (253497123) this will fill the Digital Odometer area.
After this string it will give you SoF 3.0 (or what ever version you have)
Then fault numbers or No Faults
Then your guages will systematically check themselves popping into 2 or 3 positions per guage. Then The test will end.

This will reset the computer and it takes a few driving cycles to get the error back. The Techs tried to read mine and saw nothing even as the check engine or MIL (Malfunction Indicator Light) was shinning brightely.

2 days later they plugged in again and there was the Error. Not a code but an error. Therm stuck Open is what the computer had as an error, not a code number.

[Bounty__Hunter]

No offense intended.

[indiemo]

when I check my 97 with the hold trip button, turn key three times method, it goes through the gauge cluster show and flashes the code at the very end of all that business. make sure you didn't stop watching before it was ready to flash the codes.

[jaketime81]

when it is checking it starts out at 0000000 then 1111111 then 2222222....ect. till 9's and the gages move back and fourth, after that it stops and goes back to normal operation. There are no other codes, #'s or letters.

[Bounty__Hunter]

It shouldn't go throough the guage test cycle of 0000000, 11111111. This happens when you hold the odometer reset button down, turn the key from off to run, and release the odometer reset button.

Try this:

• Key in off position
  Push and hold odometer reset button
  Turn key to run (not start)
  Turn key to off
  Release odometer reset button

[jaketime81]

Thanks for your help, Ill try it and let you know what happens.
-jake

[L33TJ33P]

your 97 may have the Old on-off flip thing. It is really odd. Some have the Flip on-off and some have the Upgraded SoF and have the Odometer button thing.

start at off
Quickly flip it to run (not start) off, run, off, run 3 times within 5 seconds Leave it on Run to see your codes.

[XJNick]

Well NONE of the above methods work on my 97 TJ.

I've tried holding the odometer button then turning the ignition switch to RUN and what I get is 000000, 111111, 222222, 333333, 444444, 555555, 666666, 777777, 888888, 999999, along with the corresponding gauge cluster readouts.

I've tried Bounty's suggestion of holding the odometer button, turning the ignition to RUN, then back off while holding the odometer button, and I get nothing.

I've tried L33's suggestion of turning the ignition to RUN, OFF, RUN, OFF, RUN, and nothing out of the ordinary happens.

AllData seems to think that the '97s can only have codes retrieved through a proper OBD-II compatible scanner. So, I guess the '97s used several different computer system variations?

[K_K_PSI_GUY]

Go to AutoZone. They will check the codes for free. Don't buy anything until you let us know what code came up. Like L33TJ33P said, just because a code calls out a ceartain sensor, doesn't mean that that is your problem. -al

[Bounty__Hunter]

Originally Posted by XJNick

I've tried L33's suggestion of turning the ignition to RUN, OFF, RUN, OFF, RUN, and nothing out of the ordinary happens.

Try one more cycle of on/off here, and look for the check engine light to flash.

[XJNick]

Good Call Bounty. Turning the ignition switch in the sequence: OFF, RUN, OFF, RUN, OFF, RUN, OFF, RUN made the computer display codes on the odometer and via the CHECK ENGINE lamp flashing.

Appears I got code 42, ASD circuit open (probably due to my imobilizer being on when doing the check)

Thanks
-Nick

[jeepin916]

ASD? thats the Auto Shut Down relay isnt it? check if the relay is messed up

[jeepdude832]

Get that exhaust manifold fixed If you have the 4.0 get the banks torque tube its the best one.