Check engine light question! [Archive] - DSM Forums: Mitsubishi Eclipse, Plymouth Laser, and Eagle Talon Forum:

: Check engine light question!

12-21-2002, 03:29 PM
I put a test pipe in now my check engine light comes on. Anyone know how to get rid of it and keep it away? Thanks

12-21-2002, 07:45 PM
Try running a search for rear O2 CEL eliminator or related words. ;)

12-21-2002, 09:49 PM
It didnt pull up anything. :(

12-21-2002, 10:17 PM
The problem is the rear O2 sensor. You can't disconnect it entirely (I'm assuming you did), without possibly getting a CE light. All it does is compare temps with the front O2 sensor, and makes sure that it's lower than what the front O2 reads. It can be hung up under the car, and left out in the air.

12-22-2002, 12:04 AM
I had a shop put in the downpipe,testpipe, and catback. I dont know if they remove the 02 sensor.Will installing a high flow catalytic convertor solve this problem?

12-22-2002, 12:23 AM
It won't necessarily fix it. Just keeping the sensor itself attached will solve the problem if that's what's actually setting it off. You can just string it up under the car with some wire or something. Normally it's right behind the catalytic converter, but a lot of test pipes need it to be removed. As long as it's plugged into the wiring harness, it'll work like it's supposed to.
I'd get ahold of the shop that did it, or look under the car to find out if it was removed. You should see the wiring near the test pipe somewhere. See if the sensor is attached to the wiring.

A lot of people just deal with it, but I know I get irritated with a constant CE light. I finally got mine to go off after a few weeks with it on. I still don't know what triggered it, but all I did was put new spark plugs in, and it went away the next time I drove it. That bright yellow kept catching my eye all the time, and it drove me nuts. If something really goes wrong, you don't know it because the CE light is always on, and you think it's just the sensor.

12-22-2002, 08:39 AM
Colonelfox. The front or rear o2 sensors have no idea what the temp of the exhaust is , they must be hot to produce a voltage though. O2 sensors are basically batteries that produce a voltage that varies with the amount of oxygen in the exhaust. They do this by compairing the amount of o2 in the exhaust to the amount around the outside of the sensor (in the atmosphere). When there is a large difference (rich condition) they produce a large voltage , small difference (lean condition) small voltage. Removing the cat and installing a test pipe will cause a check engine light on vehicles with a rear o2 sensor. The rear o2 is used to monitor cat efficiency , with a good cat it usually produces a constant voltage indicating a rich condition. Without a cat and sensor connected it will produce a varying voltage like the front o2 and ECM will know somethings up. If you diconnect the rear o2 sensor the ECM will see no voltage from it and may also detect an open rear o2 heater circuit . Get high flow cat or o2 simulator .

12-22-2002, 10:30 AM
I know they measure voltage rather than actual ambient temp, but it was easier to explain that way.
I guess I heard wrong on why it sets off the CE light. I heard to leave the sensor attached, and as long as it was reading a different O2 than the front, it wouldn't trip the CE light. :dunno:

12-22-2002, 09:44 PM
Originally posted by prty_girl
I put a test pipe in now my check engine light comes on. Anyone know how to get rid of it and keep it away? Thanks

just disconnect the battery for a little while, then reconnect it. it'll reset your ecu. the only drawback is that you have to put the code back into the stereo....which takes all of 15 seconds. or, find somebody with a logger, they can read and clear codes. good luck.