Dr. Willy

Okay so my car was throwing a p0420 for a while, which i figured was the cat. I decided to start with the 02 sensor just to see. Replaced the sensor and now i get a p0141 code after the car idels for about 30 secs- 1 min. Doesnt matter how many times i reset it with my scan tool, just comes right back. Do you guys still think its the cat? ive tried 2 other o2 sensors, including the one that i replaced in the first place and i still just get the p0141 code, it wont throw a p0420 anymore at all.

BryanM.

iTrader: (1)

P0141 is O2 sensor heater circuit malf. right? I don't have my manual handy.

If so it sounds like a wiring issue.





inbeforeRonJ@HT



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delsolproblems

You might double check the wires. You may have switched two wires when you hooked up the first new sensor and then copied it with the second. Alternatively, you may have tugged on one of the heater wires during installation, pulling it out of the next connector on the way to the ECU. Try setting a meter to ohms and check the resistance of each of the four sensor wires between the wires at the ECU and the ones at the O2 sensor. Open the passenger door, pierce a wire at the ecu with one probe and the corresponding wire coming out of the sensor with the other probe.

Dr. Willy

well this is a brand new denso o2 sensor, with a plug on the end so i didnt wire it up it came wired up. i will try the ohm thing, when i do scan it with my scanner it says not all readiness test complete, what does that mean?

Dr. Willy

i am also going to try and switching the y7 cat with my gf's y7 cat to see if that solves the problem.

delsolproblems

The heater malfunction code will not be fixed by replacing the cat. The not all readiness tests complete message means that due to the problem with the O2 sensor, the scanner was unable to determine that your vehicle was ready for an emissions test.

Former User

P0141 indicates a problem with the secondary O2 sensor heater element not the cat. Did you replace the primary or secondary O2 sensor?

Dr. Willy

i replaced the secondary 02 sensor, what i dont understand is why it was throwing the code for the cat, like the cat was bad at first but now it is not.

delsolproblems

It can take a little time for code 0420 to pop up. If you let the car sit for a time while you work on it, the cat can continue catalyzing compounds inside of it so that there is less to absorb by the time you turn the car on again. With less crap inside it, it can work better for awhile until it gets coated again. A perfectly working cat should keep up with the exhaust, catalyzing compounds as quickly as they flow through but a failing cat can allow more build-up because it isn't keeping up with the exhaust. It all depends on how bad the cat is.

Dr. Willy

okay, so here is what i found out, if the car is cold and i start it up, it throws the cel for po141 after the car has ran for about 30 sec, if i then take the car out and drive it and it gets warmed up, then delete the cel, it doesnt come back, until the car cools back down and is started again, im guessing possibly bad ecu is the only thing i can think of i checked wiring and everything is fine there.

Former User

Do you measure 10-40 Ohms across terminals 3 and 4 (heater element) of the new O2 sensor?

Dr. Willy

i just got home, keep in mind the car was hot so i dont know if this makes a difference? i had my voltimeter set to 200k ohms rating, not sure if this is the right setting either? but i had 69.3 was my reading between 3 and 4, im assuming it was 3 and 4, the other 2 colors were black which i figure was ground, and these were the other 2 wires that were colored. Let me know what you think, thanks

Former User

That's too high and may indicate the problem. Measure again when the exhaust system is cooler.

What year/trim?

Dr. Willy

its a 2000 dx, and i will try in a bit once it cools off. Thanks ron

Former User

You chose the 200,000 Ohm scale. Instead, you should select the lowest scale, such as 20 Ohms or 200 Ohms.


The two black wires actually correspond to terminals 3 and 4. Terminals 1 and 2 have white and lt green wires.

Repeat the Ohm measurement between the correct terminals (for the two black wires) and use the lowest Ohm scale.

Dr. Willy

i will do tomorrow when i get home from work and will report back

Dr. Willy

okay on termanals 3 and 4 (the two black wires) i am messuring 4.6-4.8 on the 200 ohms setting. Im guessing this is withing range?

Tico Loco

Hi I am form Costa Rica. I am a amateur engine builder and I race my Honda Civic Ex D16z6 engine.

You can burned the sensor with the ohms test. Be sure to measure the ohms at the heater wires, if you try to ohms test on the sensor wires you can burned the sensor.

The sprimary sensor control the fuel mix, the second is to verify the cats eficiency. In some vehicles is your second sensor is not working could give a wrong code, like a bad cat.

Check the volts coming from the plug in the heater wires from the wiring system. If their is no volt, the heater do not work.

Former User

The resistance is too low (4.6-4.8 Ohms). It should be 10-40 Ohms = bad O2 sensor.

Dr. Willy

i actually think i found the problem, the o2 sensor i have is a front sensor, im guess it wont read right as the 2nd sensor cause i put the old o2 sensor back, and no more cel.