O2 Sensor (bank 1 - Sensor 1) Front Or Rear?

[jdob]

My wife's 2000 Kia Sephia has the check engine light on with the following codes:

P0134 - O2 sensor CKT no activity (Bank 1 - Sensor 1)
P0135 - O2 sensor heater circuit malfunction (Bank 1 - Sensor 1)

I am hoping one of the O2 sensors is faulty and that changing it will get rid of the codes. But which sensor is (Bank 1 - Sensor 1)??? Front or Rear???

State Inspection is due again before the end of September...Any help is greatly appreciated!

[Night-Hawk]

it should be the first one which is the one nearest and easiest to access. But if its not that much trouble, replace em all. How many miles?

[jdob]

I messed around a little bit today trying to figure out which was which. You can see both of them looking down into the front of the engine with the hood up. The one closest to the engine is "Bank 1 - Sensor 1" and then the second one about a foot or so further away from the engine, but before the cat is "Bank 1 - Sensor 2". Both of the connectors for the O2 sensors are easy to see and get your hands on. Now the worst part of the whole deal is buying a new one! The local auto part stores want between $120 to $140...the cheapest I have been able to find them is about $90 on Ebay...

My wife's 2000 Kia Sephia has about 68k miles on it so far...

[jdob]

Well - I installed a new 02 sensor (Bank 1, Sensor 1) and cleared the old codes with my Actron now I have the following codes:

P0131 - O2 sensor circuit low volts (Bank 1 - Sensor 1)
P0135 - O2 sensor heater circuit malfunction (Bank 1 - Sensor 1)


So I still have P0135 and my P0134 has been replaced by P0131. Does anyobdy have a clue what may be the problem??? Any help is greatly appreciated. Thanks!

[mmthomas]

1996 Sephia - I have P0135 code set. Inspection due this month, Texas.

I have checked the continuity of the heater by unplugging the sensor connector and checking with VOM. It is good. I guess I will have to start looking at wire harness.

I fear that if I have work done by shop they will replace the sensor and cost me money, not solving the problem. And tracing wire problem is a money hungry witch hunt at a shop.

By the way, the 2nd sensor, in the center of the exhaust pipe under the car, has different gender connector on harness than the first sensor under discussion. I reseated both connectors to see if that would solve the problem. Didn't.

By the way, airchecktexas, the state agency in control of testing, has a bulletin that the non-continuous monitors in the 96 Sephia will often not go to yes (complete) and the inspection can be done by exhaust measuring in this case. I have got my monitors to go to yes by driving three round trips of over 50 miles each.

I am using the obd tool from http://www.obd-2.com/

[1fastkia]

see my for sale thread. I have a sephia parts car. all I have left for 02 sensores in the 2nd one. 30 bucks shipped for you if you are in america. if not shipping will be more...

[KiaMech]

If you've got resistance through the heater, then it should be good. Check for 12V at the harness in the heater circuit. If you don't have any voltage, then check the fuse.

[mmthomas]

Does the computer actually measure the sensor resistance when setting the heater code?

Or is that code a guess, and that some other problem (sensor not working) causes the computer to think the heater is bad?

In other words, does oxygen sensor heater code actually mean a directly measured heater problem has been found?

[KiaMech]

12V is sent to the heater circuit from the fuse box. The computer expects to see some voltage coming from the other side of the heater circuit, and if it doesn't, then this code it set. There's very few things that could cause this. Bad O2 heater (which you already tested), 12V not found at the heater (blown fuse, bad wiring, bad connection), wiring problem between the O2 sensor and the ECM (bad connection or short), or bad ECM.

[mmthomas]

12v is at the heater circuit for the oxygen sensor connector when the engine is running. Not present when just ignition switch on. Connector unplugged to measure pins.

I have Hayes manual for Mazda Protoge that I am using to understand the wiring. The colors of the wires are not the same and the connector genders are different on the KIA from the Hayes manual for the oxygen sensors. Hays shows body connector to be female. It is male. Sensor connector is female.

It appears from the Hayes diagram that the PCM supplies ground to turn on the heater. How would it sense heater on if it is supplying ground? I would not think it would measure current flow?

There is a smell of unburned gas from the exhaust while idling after running. Something is wrong.

Maybe I should just replace the sensor, even if I have nothing to show it is wrong? Car has 75,000 miles (1996).