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Discussion Starter #1
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!
 

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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?
 

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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...
 

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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So I still have P0135 and my P0134 has been replaced by P0131.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!
 

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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/
 

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2015 Buick Verano "Leather Group", 2015 Kia Optima Hybrid
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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...
 

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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.
 

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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?
 

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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.
 

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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).
 

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What was the resistance of the heater when you checked it? It's the two black wires so you know you're checking the right ones.

The PCM only checks the heater circuit once per drive cycle. I'm not sure if it checks it before or during the time the heater operates. If it checked it before, it would check for voltage. If it checked it during, then it would probably monitor current.
 

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I just used continuity mode; not resistance. The buzzer sounded. I will measure again when I get time for troubleshooting.

Note: the MIL comes on at the beginning of the second drive cycle. the oxygen heater non-continuous monitor also completes then.
 

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After removing Oxygen Sensor I tested heater continuity again and it was bad (no resistance). Somehow I measured full continutiy while in the car. Probably a short in the connector adapter I used during measurement.

The sensor body in the manifold was covered with black carbon that brushed away easily.

I replace the OEM sensor with Boch generic. This involved cutting the KIA connector off the old sensor and splicing a new connector supplied with the generic onto the old connector. The instructions told how to match the wire colors.

Old sensor was not partiularly hard to remove. Used AutoZone loaner tool with wire gap in socket.

Have driven car about 50 miles with no fault. Both O2 non-continuous monitors have completed (ready).
 

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I have the same problem like the O2 sensor problem as the fault code is PO141, my mechanic has check the voltage and it has confirm that the ECU is supplying voltage to the heater circuit of O2 sensor, no fuse or connector problem so where does the problem lies which trigger to have the fault code.

Anyone can advise further?
 

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That's good that there's voltage at the connector, but did he check the resistance of the O2 heater?

That code is for the O2 sensor heater current being either too low or too high.
 

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Originally posted by KiaMech@Nov 15 2005, 01:04 AM
That's good that there's voltage at the connector, but did he check the resistance of the O2 heater?

That code is for the O2 sensor heater current being either too low or too high.
Yes, my mechanic tap on the O2 sensor to test out the resistance for it, there is reading so resistance is ok. Then we tap the wire connector which connect the 2nd O2 sensor, it shows voltage reading so ECU is supplying voltage to the O2 sensor but just don't understand why there is still a fault code that says PO141, Heater circuit malfunction for the 2nd O2 sensor.

Another mechanic was suspecting that problem could occurs at the wire harness some where cos the ECU did not get the signal or voltage. What is the possibility of the problem and any solution to this?
 

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Well, assuming that the resistance is in spec (just because there is resistance doesn't mean it's the "correct" resistance) then the problem would have to be the wiring or the ECU. Do you know if they checked the resistance through the wiring between the ECU and the O2 sensor?
 

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Originally posted by KiaMech@Nov 16 2005, 08:55 AM
Well, assuming that the resistance is in spec (just because there is resistance doesn't mean it's the "correct" resistance) then the problem would have to be the wiring or the ECU. Do you know if they checked the resistance through the wiring between the ECU and the O2 sensor?
For the 1st O2 sensor, my mechanic managed to find that the tampering of wire affect the resistance and by observing the signal pattern from the Oscilloscope, it is very unstable.

My mechanic has managed to improve on the wiring of the 1st O2 sensor and the signal is back to normal now but for the 2nd O2 sensor, the ECU still cannot get any signal from the O2 sensor though we tap from the wire from behind of connector for the 2nd O2 sensor, there is signal and voltage.

So now problem exist between the 2nd O2 sensor connector to the ECU, there seems a leakage somewhere. My mechanic suggest to me that he will do a wiring directly from the 2nd O2 sensor to the ECU, what do you think?
 

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That sounds like a good idea. There aren't any connectors between the sensor and the ECU, so there must be a break in the wire. Running a new wire is the quickest fix.
 

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Originally posted by KiaMech@Nov 17 2005, 12:16 AM
That sounds like a good idea. There aren't any connectors between the sensor and the ECU, so there must be a break in the wire. Running a new wire is the quickest fix.
I am back with some updates to my problem.

Just last thursday, my car break down along the expressway of my country, all the indicators just lighted up and went off again, it happens few times and engine stalled. Crank to start car but it dies off after a short while, I quickly shift my car to the road shoulder while it is still moving though have no control on the speed any more.

My car was towed to the workshop and they check that problem lies on the Cam and Crank sensor faulty, replaced it but car still not working fine as it will shake a bit after a while after letting it to idle.

Change to a Matrix ECU but reprogammed to suit my car, everything works fine now but seems idling a bit noisy and engine noise a bit louder than before but the 2nd O2 sensor heater circuit malfunction problem still exist, check light still comes on. Really headache and my mechanic says problem lies on the engine harness but if want to replace the whole harness, the cost will be very high.

I have check with my dealer to refer to the parts catalog and can see that there is 2 seperate harness there, one is engine harness and the other is ECU harness, if really want to replace harness also dun know which one to replace, do you have any idea on this?

Can help me on this?
 
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