O2 Sensor (Upstream Air/Fuel) on a 2.7l (code P0135)

Anyone ever have a a/f burn out after only a few hundred miles? I replaced mine with a Denso and all was good for about a week. CEL back on with the code stating heating element malfunction bank 1 sensor 1. Checked connection; it was secure. Naturally, this is the expensive one.

 

OK, I replaced the bad sensor with a new Denso on Wednesday. Drove 100 miles, CEL still on after 2 days. Had Auto Zone read the code tonight. P0135 - heating element malfunction. I'll buy one bad sensor, but not two in a row. Or is this the earlier code just not cleared yet? They could not tell me any details about the code.

Anyone know how these codes work? I usually see them disappear after driving 75 miles. Or could there be something up with the plug or wiring?

 

PO135: This code relates to the UPSTREAM O2 sensor.

The following should give you a good reference as you move forward.
http://www.troublecodes.net/pcodes/p0135/

 

Yes, the upstream sensor. Downstream sensor is also new about a year or so ago. The second video had the info I was looking for, which was checking the circuit for power and the plug for a short. I'll have to see if the specs for this sensor are in the service manual.

 

A common mistake that many make is buying the cheap code reader (around $50), the cheap tool simply gives the codes that are flagged, there is no real time data. The better tool ($100-$200 range) should have software that gives real time data, this is a huge advantage when trouble shooting DTC's.

I bought the cheap tool, I later bought the better tool.

 

I don't have a code reader, but good to know should I get one.

I only had time today to pull the plug and visually check the wiring and then reseat the plug. Everything looks fine, and the connection snaps together tight. The service manual has some info on the resistance through the sensor, but I did not see how to check the circuit for power. There are four wires to the sensor, the one in the video only had three.

Any info on testing the circuit would be appreciated.

 

A multimeter can be use to measure the resistance of the heater.

http://www.autozone.com/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f80378d08

Using an ohmmeter, measure the resistance between the terminals +B and HT. Resistance: 11 - 16 ohms at 20°C (68°F)



Schematics: Please check your under hood I.D. number to find your exact model, (i.e. - 2RZ-FE, or 3RZ-FE..etc...etc...) Search the page as needed.
http://www.autozone.com/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f80378d17

 

Thanks. Sensor checks out. It should, it's brand new. The power to the heater must be on one of the other two wires. I'm away from home for awhile but I have my meter with me. The battery is dead though, so when I have a chance I will pick one up and check it again.

 

Also check the wiring from the computer to the sensor heater element. A bad connection here will also throw the code because no current can flow to the heater.
Make sure the ground connections to the computer are good. That sensor heater draws about 8 Amps and the current sense circuit will not work correctly with a bad ground.

 

8 amps is pretty heavy for an auto. I'll have to check that connection.

 

While on vacation I had some time and help to check this out further. We followed the service manual troubleshooting guide and metered the connections. All within spec. Wiring and plug looked very good. Checked the relay, which seemed ok, but then we noticed there is another relay of the same type. So we swopped them. Checked all relevant fuses for continuity. Found no issues.

Due to pulling the fuses/relay, we inadvertently cleared the code. So now had to wait out driving some miles to see if the code returned. In the past after clearing this code it would return within a few miles. But now after 250 miles, no code.

We suspect that reseating the plug or relay may have resolved the problem. I'm keeping an eye on the CEL, and hoping this is it.

 

Bad news. After 275 miles and about 7 days, the CEL came back on. Haven't read the code yet, but am betting its the P0135. @#$%!

 

On the 2.4l 2rz engine there is a ground connection on the right front side of the cylinder head just below the valve cover. This connection has several parallel wires that go directly to the engine control module. It is crucial that this connection is solid because of the high current draw of the Bank 1 O2 heater I mentioned before. You have the 3rz 2.7l, but I suspect that the grounding is similar.

Check the physical condition of this connection.

Too often electrical troubleshooting is focused on the power side instead of the ground side because everyone assumes that ground is OK.

I fell into the trap of measuring a low resistance to ground with my digital Volt-Ohm meter and thought the connection was OK. Your normal Volt-Ohm meter is not good enough to verify this ground connection.

Sorry for going on, but I am an EE.

 

I have not done this, but will this weekend. Coincidently, I suspect I am having a grounding issue on my skid steer loader. Everything checks out fine until an electric load is put on the system and the circuit fails. I will be looking at this today, and hope to track it down. I find these problems to be very tricky, and counter intuitive to troubleshoot. At least for a non-engineer.

 

We read my new trouble codes on the weekend and were surprised by the results. The codes this time were P0441, P0442 and P0446, which some researched showed could be generally attributed to a bad gas cap. No sign of the P0135.

The truck has thrown these codes before, usually after someone else has filled the gas tank and not twisted and clicked the cap enough to seat the seal. So we reset the codes and I bought a new gas cap. I will have to continue to watch the for CEL because it's hard to sure that anything will solve this seemingly endless stream of codes this truck throws.

 

New gas cap and CEL still out.

You can really see the difference between an old cap and a new one. The seal really seats tight. at least it feels that way. And you can see the differences in the shape of the seal. The old one is significantly compressed, and may be prone to leaking.

No CEL so far.

 

Yes, your code can linger on after being fixed. And unless you clear the DTCs, and drive the vehicle to pass the monitors, your CEL will stay on until it drives N amount of times under proper working conditions.

I.E. I just changed my evap pressure sensor. CEL was on. changed the sensor, checked voltage on the ECU at the connector, everything was fine. CEL still on. Code scanner said it would do that for several "trips". and thats right. after 3 10 minute drives, the CEL turned off. BUT! the codes are still in my computer. So I'm assuming it will just go away after several more "trips".

 

CEL back on. Haven't read the codes yet.

 

The return of codes P0441, P0442 and P0446. So I guess the gas cap didn't fix anything.

At this point, I think the purpose of this email (MIL P0135) has been served. I may start another for the new codes since they are repeating. Thanks everyone.

 

P0441, 0442 and 0446 for me too. Keep me posted if you solve it.