Check Engine light on - Fixed Probem and Light Back on

Check engine light came on.  Put on machine to give me code.  
Code was P0136 (O2 Sensor Circuit malfunction)  Mechanic Replaced the O2 sensor with a brand  new one and couple days later, Check Engine light came back on.  Not sure what to do now.  Live with having Check Engine light on?

[ARMYtango]

Do you know which O2 sensor was replaced?
There are usually 2 sensors...one Before the Cat and one after the Cat.

Chances are, the OTHER sensor needs to be replaced.

I would double check to make sure you are getting the same code first.  If so, you may need to replace the other sensor.

It was toward the middle part of the engine.  We had to take a metal cover (which took a long time to cool) off held on by three screws and the sensor we replaced was right underneath the metal plate on the right side of the engine.

[ARMYtango]

What kind of vehicle is it?

If you look underneath the car , you should see another sensor just AFTER the Catalytic Converter.  If you are getting the same code, then chances are that would be the sensor to replace.

[conniecartech]

armytango has a good point. code p0136 is for sensor 2, which is after the cat converter. from the sound of it the tech replaced sensor 1 which is before the converter. after he replaced it he probably cleared codes, which is why the light didnt come back on right away.

but if he replaced the wrong sensor the problem was still there. when the conditions was right to set a code, it did and the light came on. i bet a rescan would show p0136 again. another code means a diffrent problem.

u should go back to the tech and find out which he replaced. u could look yourself and see which sensor, 1 or 2, looks new. if he replaced the wrong one, he owes u one. hope this helps.

IN ADDITION TO REPLACING THE WRONG SENSOR, You're mechanic coulda made a bunch of mistakes that alot of amatures do. The first mistake coulda been changin the sensor PERIOD. Just because a code is set DOESN'T ALWAYS MEAN THAT THE SENSOR IS BAD. If there's a problem with the electrical circuit that feeds the sensor, the connector that fits onto the sensor, or a problem with the computer the SAME PO106 code is gonna set.

JUMPIN IN AND AUTOMATICALLY CHANGIN THE SENSOR JUST BECAUSE A CODE IS SET IS WRONG,WRONG, WRONG!!. YOU GOTTA CHECK EVERYTHING I MENTIONED ABOVE FIRST. THEN IF ALL THAT CHECKS OUT, THEN YOU CHANGE THE SENSOR.

A couple of other mistakes he coulda made would be to use an aftermarket or universal O2 sensor. Alot of amatures do this because aftermarket and universal sensors are cheaper and they don't realize that they could be dealing with a car where an OE sensor MUST BE USED.

Post the year, make, model and engine size of you're car and we'll help you more.

1996 Dodge Intrepid, 3.3 V6.

Thanks for postin the vehicle information, but you didn't realize that you had to answer the questions I asked you as well. I'm gonna make easy for you and post the questions again here and now. This way you won't have to go back a read threw them again.

First of all if it turns out that you're mechanic changed the wrong 02 sensor, then case closed and we're done with this issue.

If he didn't install the wrong 02 sensor, then here's what you gotta ask him, and then post back the answers so we can see them.

Did you check the 02 sensor before changin it to make sure it was defective, or did you just change it without checkin it?

Did you check the circuit and wire harness that feeds the 02 sensor, and did you find them all in tact?

Did you check the wire connector at the 02 sensor and find it to be on tight and free of corrosion?

Was there a signal from the ECM to the 02 sensor?

Did you use an aftermarket or universal 02 sensor?

FYI, CHRYSLER VEHICLES ARE LIKE FORD VEHICLES. WHEN IT COMES TO THINGS LIKE SENSORS AND FUEL PUMPS, IF YOU WANNA AVOID PROBLEMS AND HEADACHES YOU GOTTA USE OE PARTS.

Hello jsteven30,

This will be a big help to you're mechanic. Please print it out and give it to him or her.

P0136 - Heated Oxygen Sensor Circuit Bank 1 Sensor 2.

A downstream oxygen sensor (or sensors) is constantly being monitored for minimum and maximum voltages. PO136 will set anytime voltages fail to rise to the   calibrated thresholds of the sensor or sensors.

Connect a digital voltmeter across the 02 sensors circuit. A voltage needle that is bouncing around indicates that the sensors circuit is failing to close, thus compromising normal voltage flow.


Things to check before changing the sensor.

A wiring problem between the ECM and O2 sensor.
Damaged or contaminated O2 sensor.
One or more exhaust leaks.
Crossed O2 sensor wires.
Pinched or corroded wiring.
Loose or corroded wire connection.
Application error (wrong sensor is being used)
Pins at the sensor or sensors connector that are bent or pushed back to far.
Wires on the verge of separating from the sensors housing.

I hope this information helps you. Thank You.

Mrs. Connie Carlson
 

[discretesignals]

In addition to that the sensor is heated.  That means you have to have the correct heater voltage and ground at the O2 sensor's connector.  The O2 sensor won't function properly if its heater isn't working.