check engine light on but no codes???

mxkiller125 · Nov 6, 2009

My check engine light came one today on my 97 jeep cherokee so i did the key trick and the only code that shows up is 55...but 55 means end of codes. Does anyone have any idea why the light could be on??

joe_peters · Nov 6, 2009

Most OBDII will NOT give you codes with the key trick--I believe that ended part-year 1996.

This link: http://www.geocities.com/JeepI6Power/obd2.html

Codes with RED background will give a CEL.

88xjlover · Nov 6, 2009

Run into a auto parts store like autozone or o'reilly's and ask them to borrow a code checker. plug in and turn "on" (dont start the jeep just to the on position). The port is just under the knee panel on the left side by the door jam.

arsxj1 · Nov 6, 2009

mxkiller125 said:
Does anyone have any idea why the light could be on??

Alot of the time its a gas cap. Atleast on alot of cars. I hate dummy lights :wierd:

hawk_sixsix · Nov 7, 2009

Works on my 97. Don't remember exact month/year DOM.

mxkiller125 · Nov 7, 2009

joe_peters said:
Most OBDII will NOT give you codes with the key trick--I believe that ended part-year 1996.

This link: http://www.geocities.com/JeepI6Power/obd2.html

Codes with RED background will give a CEL.

I have use the key trick before to diagnose problems and one time it gave me a code 25, which is red in that list. My buddy has a code checker so ill see what that tells me.

trippled · Nov 7, 2009

you need a special to use a code reader on obd1 jeeps. they are kind of hard to find. if you are getting a code 55 your jeep is not a 97. all obd2 systems are standardized (as of 96) and all engine related codes start with Pxxxx (powertrain). you may have a pending code (such as a misfire) which the computer has found a problem but is waiting for it to happen again to verify the problem, however a pending code can only be seen with a code reader.

Matthew Currie · Nov 7, 2009

I think on a 96 or 97 the two OBD systems coexist, but you're not reading the same set in two different ways. The key trick will work for the engine codes that were available with OBDI, but I don't think it will pick up added OBDII codes, including transmission codes, so if it's one of those, you'll get the light but no readable code with the key.

birchlakeXJ · Nov 7, 2009

Matthew Currie said:
I think on a 96 or 97 the two OBD systems coexist, but you're not reading the same set in two different ways. The key trick will work for the engine codes that were available with OBDI, but I don't think it will pick up added OBDII codes, including transmission codes, so if it's one of those, you'll get the light but no readable code with the key.

My understanding as well...get a code reader or a scan tool on there and I'm confident you'll get a code to interpret.

mxkiller125 · Nov 10, 2009

Well the check engine light just went off on its own, i didnt even do anything. It seems to be running fine so i guess ill just let it go haha. Thanks for the help tho

Matthew Currie · Nov 10, 2009

My second O2 sensor does this periodically. I've stopped worrying.

check engine light on but no codes???

mxkiller125

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