Last week I was working on a Mazda v6. I had a code for both sensors. Replaced both with universal Denso. Transformed performance and cleared codes. One was for o2 out of range and heater circuit. Other code was just out of range. So it happens!

 

I'm leaning towards replacing them but just wondering if I should get the auto or manual ones.

Like I've said, I've swapped a couple, including the ECM to manual, and continued using the o2 sensors that were obviously auto. But now I've changed the ECM to manual.

I just don't see why I would need specific auto or manual o2 sensors but I'm certainly not an expert on the psychics of oxygen sensors.

 

I have exhaust shop weld in screw in bungs and then use universal type o2. Just splice in the wires. It's much cheaper and work great. Been using Boach universals in my turbo 4runner flawlessly for 10k. Work great despite how Yota folks feel about Bosch anything.

 

The differences between auto and manual are not in the sensors, but in the wire length in 4Runners with the 3.4. Cali and non Cali however, you need A/F in front to match the ECM if the ECM is '99-'00 Cali. or post MY 2000. Other than wire length, there are only three types of exhaust sensors used in 3G 4Runners with the 3.4: O2 flange, O2 screw-in, and A/F flange. I assume it's the same for Tacos. What year and model did the ECM and engine come from?

There are too many reports of problems with Bosch sensors on Toyota engines for me to consider using them even if they worked for one poster.

 

Sometimes a glob of dielectric grease on the pins can help. May want to check the Maf. Keep in mind that in closed loop its not just the o2's that input information. I mean at this point it wouldn't hurt.

 

The ECM is a 97 manual,4x4.

Vital. Can you explain how the MAF could impact the o2 heater codes being thrown. The MAF was damaged in the crash that made the Runner a donor. Just the lip of the flange that inserts into the intake boot was snapped of a bit. A small piece about the size of a dime but that still shows it took a good hit. No MAF related codes or anything else that seems faulty for that matter.

I decided to just try it before sourcing a different one and it had seemed fine.

 

Still fighting this. Getting random codes p0135 and p0141. Front and rear o2 heater circuit malfunctions. Sometimes it'll go a week with no codes. Then there they are.

Have cleared codes, driven, o2 heater monitor will run in 5 minutes and pass along with o2 sensor, then sometimes it'll code both of them out of the blue. Did it twice tonight.

Absolutely frustrating.

Any thoughts on having no muffler on it. Pipe is cut off about 18" after last o2 sensor. We were thinking the lack of a muffler is causing the heat to leave the exhaust too soon. No back pressure building up. No heat buildup. Complete guessing on that but it was a theory.

Still haven't bought new sensors but I guess that's next.

If I throw $200 in new sensors with the same problem, I'm gonna be pissed.

 

Is there some kind of crude test for the o2 sensors involving starting fluid and a rag? Start with replacing the upstream o2 an see if that code goes away. The downstream measure cat efficiency only. You might only replace that one after if/after the upstream code clears. I hate that you're having his problem but what else could it be at this point?

 

Denso 234-4206 Oxygen Sensor by Denso http://www.amazon.com/dp/B000C5UFOY/ref=cm_sw_r_udp_awd_Uv9fub1QWXRH6

Same sensor, just no factory connector. All you have to do is cut and splice wires into factory connector. Half the cost of what you propose.

 

No muffler is not an issue. How big is the exhaust pipe? BBP had similar issues and it wouldn't go into closed look. Check all of the engine grounds. I have a feeling it may not be pulling good grounds to ecu. Or the pins in the ecu plugs are loose.

 

Yeah I have very little restriction and a 3" exhaust and have no problems. This is not your problem. There was a guy not long ago, I forget which sub that had bad running problems an traced it finally to a missing ground wire from the manifold to firewall, for example. So yeah I second vital. The ecu needs to gets proper power and grounding. And good ground from battery to body and block.

 

Vasinvictor thanks for the link. A lot cheaper!! These will work for front and rear right? I have read the two are the same spec wise, but vary in wire harness length. If this is the only difference, and I am soldering new harness on them anyway, can't see how it would matter.

Guys I am as confident as can be in the grounds I think. Good 2 ga. To the block, 2 ga. To the frame from the block, 8ga. To the firewall from block. Already took apart the main ground spot on front, driver of intake, cleaned up with wire wheel, dialectical grease, retightened. Good ground for ECM, ECM body even grounded. Unless something is wrong inside the harness itself that I didn't get into. I can't really ground the sensor itself as the ECM sends he ground for the heater, not power. It gets constant ignition power through the EFI relay. The white/blue wire I know you guys know.

 

Dumb question, but where did you put the dialectic grease? I only ask because dialectic grease is an insulating grease, meant to stop/prevent an electrical connection, so if you put it between the block/frame/body and connector or connector and bolt, chances are you're blocking your grounds.

 

That's my understanding of them as well. Only difference is the connector/wire length.

 

I'll check out the dialetical grease situation.

I should also mention that it does go into closed loop as it should.

 

What did you figure out?

 

Connectors are only different between A/F, O2 flange and O2 screw (the two types of universal sensors; note that there is NO Denso universal for the A/f sensor). Same sensor means same connector. Only difference is wire length.

 

Not a damn thing. Waiting for new o2 sensors

 

Back at this after getting sidetracked.

My guy I know works at autozone and I can get 30% off the sensors and I can return them if that's not the issue. This is better than eating the money if I find out that's not the issue.

However, they only have the upstreams in stock and the down are a two week wait.

They are denso.

I'm thinking that they're the same other the wire lengths which doesn't matter cause I habe plenty of harness length anyways.

Was gonna buy two upstream for front and rear.

Any objections?

 

I am of the opinion that you can use the same denso sensor for front and back. Cut and splice or otherwise match the wires up. I would, however, just start with the front sensor. See if you can get that code cleared. The rear o2 can be simulated out, or you could go ahead and purchase another sensor. But if your parts guy will let you return them, then whatever man. I really hope that fixes it.