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Built and raced five front-engine dragsters for fun at LACR in Palmdale, now closed. With my small-block Chevy engines, to up to 153-mph at 8.71. Too bad, it was such a good track, well run without NHRA.

Now own a 2004 Extended Cab 2-door 2 wheel drive 3.4 L Tacoma since new. Nice truck with 115,000-miles on the odometer.
 

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My 2004 Tacoma, 3.4L, Extended cab, 2-dr, 2-wd recently threw me a CEL with a P-0031 code. The stamped part number from the original bad sensor is: Toyota 89467-35060.

Every forum post and ebay ad cross references this to a Denso 234-9001, which I purchased on ebay.

After a :20-minute very easy install, I took it for a test drive. The CEL light was OUT but the truck surges at all speeds except with the throttle mashed. Scanned the truck and it showed "no codes", but the surging is not right. I unplugged the sensor and took the truck out for a drive and it drove normal with no surging, but with the CEL lit.

Talked with my drag-racing friend who is a Lease-Return Mgr. for the local Toyota dealership and he surmised that the real Toyota part number vs the Denso 234-9001 has to do with California. Has anyone heard of this before?

Am trying to get the ebay vendor to replace my Denso 234-9001 sensor to try out, but fingers crossed on that one! The Toyota part 89467-35060 is very expensive, close to $200 which I would rather not spend if I don't have to.

Any comments from those who might have had this problem....and found an answer?

Dave
 

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The code is for the A/F sensor correct? What is your A/F ratio in closed loop? Should be 14.7:1

California emissions spec trucks have some sensors different than Federal spec. Check your door codes/ViN. I forget which letter or # designates it.
 

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My ebay vendor says they are sending me a replacement Denso 234-9001.

Yesterday I visited the local Toyota Parts Dept. and measured the Heater ohms of the Toyota 89467-35060 which measured 2-ohms, very close to the Denso which measured 1.8-ohms.

Am really hesitating to purchase the OEM Toyota part for $200 in case it doesn't work. These are non-returnable once purchased. The Denso now in the truck causes the engine to constantly surge and basically run terrible even though the CEL is not lit. Will try the replacement Denso when it arrives.

The battery was left overnight with the Negative lead disconnected. No change. There is no AFR that I can see on my OBDII CAN scanner to see what the fuel ratio is, but I suspect it is lean because of the way it is running.

When this problem is sorted out, I will definitely post the solution. Anymore suggestions out there?

Dave
 

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2004 California Tacoma 3.4L - P0031 Code

Anyone out there had success with replacing the Toyota AF Sensor 1, p/n 89467-35060 with the Denso 234-9001?

After getting the CEL and scanning to get the P-0031 code, the front AF Toyota 89467-35060 sensor was replaced with the Denso 234-9001. Result was that the CEL lite went OUT, but the driving down the road, the engine pulsates and surges. Not nice to drive.

One of the Heater wires (black) on the sensor was cut. Now engine runs smoothly but CEL lite is ON and scanner shows P-0031 code.

The Denso unit cost $40 on ebay, the OEM Toyota 89467-35060 costs about $200 and once purchased, there is no return if problem is not solved. The ebay vendor says they are sending a replacement new Denso unit, but I'm still waiting.

Sorry if this post shows up in the wrong place. Am trying to figure this forum out.

Dave
 

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My User Name seems to be: User Name

Have found no way to change this. No answers from webmaster. Any help out there?

Dave
 

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Anyone out there had success with replacing the Toyota AF Sensor 1, p/n 89467-35060 with the Denso 234-9001?

After getting the CEL and scanning to get the P-0031 code, the front AF Toyota 89467-35060 sensor was replaced with the Denso 234-9001. Result was that the CEL lite went OUT, but the driving down the road, the engine pulsates and surges. Not nice to drive.

One of the Heater wires (black) on the sensor was cut. Now engine runs smoothly but CEL lite is ON and scanner shows P-0031 code.

The Denso unit cost $40 on ebay, the OEM Toyota 89467-35060 costs about $200 and once purchased, there is no return if problem is not solved. The ebay vendor says they are sending a replacement new Denso unit, but I'm still waiting.

Sorry if this post shows up in the wrong place. Am trying to figure this forum out.

Dave
Wire was cut on the new O2 sensor? Definitely need the vendor to swap it for you.
 

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Digger Dave would be okay with me as a User Name, that is what I originally thot I had. Thanks to ShowStop for sticking with me thru all this. Would like to talk with you.

Received new replacement DENSO 234-9001 today. Before changing it out, the battery Negative was disconnected and after interruptions, sensor was replaced with new. Battery reconnected after an hour, key to ON, no codes showing, and started truck. Seemed fine in the driveway, then took it for a 10-mile drive. Still surging, same as before.

Sure do not look forward to shelling out $200 for the OEM Toyota Sensor 89467-35060 only to find that the problem is still there. Before the CEL and code P-0031 last week, the truck was running fine. Even now, if the sensor is disconnected down at the plug, the surging goes away, but the CEL remains. Maybe California Emissions has something to do with this?? BTW, the Heater ohms measurement is the same for both Denso sensors and the new Toyota 89467-35060 sensor measured yesterday at the Toyota dealer was within .2-ohms. I'm baffled.
 

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Changed to Digger_Dave (with the underscore between the words) since Digger Dave is already in use.

You might want to check your electrical connections to see if something is grounding out or you have a bad connection upstream. Do you have 12VDC on the 2 heater wires? Does the ground wire show continuity to the body? Do you still have the old part? Does the surging happen when you re-install that part? All things to check before looking at replacing with OEM. Again, I've never heard of people having issues with Denso parts.
 

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Thanks for the User Name change.

Recap: OEM Toyota p/n 89467-35060 AF Sensor on my '04 Tacoma 3.4 L Heater wires are open, gave Code P-0031. A Denso p/n 234-9001 was purchased.

Replaced AF Sensor with Denso 234-9001 which cleared the CEL but engines surges. Not good.
One black Heater wire was cut as an experiment, CEL re-appeared but surging stopped, it ran smoothly.

Installed a second Denso 234-9001 (both brand new), CEL cleared but engine still surges. If this sensor is disconnected, CEL comes ON, engine surging reappears.

Since OEM Sensor Heater was bad, the 4-wires were cut at mid-point to have a plug with wires to measure voltages coming to the AF Sensor from the ECU.

Key ON but not running, one Heater wire (both are black) shows 12+Vdc, the other shows 2.3+Vdc to Ground. None of the four wires shows continuity to Ground. I put a clip-lead from the 2.3v black wire to Ground which I shouldn't have done. It triggered a 2238 Code so Battery Negative disconnected, clip lead removed, Code erased with Scanner, now back to original problem above, realizing that is probably a good way to damage the ECU. Does anyone have the voltages coming from the ECU to this AF Sensor? When this problem is solved, all this information will be posted in case it might help others with similar problems.

Am very interested in the comment that "I've never heard of people having issues with Denso parts." I'm sure it is not a problem with the Denso part, but is this Denso 234-9001 compatible with the Toyota 89467-35060 in a California truck?

It sure appears that this problem is in the AF Sensor Heater Circuit. The ohm's reading on both Denso Sensors is 1.8-ohms minus meter error of .4, total 1.4-ohms. Will visit my local Toyota Parts guy again today and re-measure the ohms on a new Toyota 89467-35060.

Am going to keep at this and try everything else before shelling out $200 for the Toyota OEM part.

Thanks a million for the help and suggestions.

Dave
Saugus, CA
 

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In previous post this morning, there is a correction to this sentence:

Installed a second Denso 234-9001 (both brand new), CEL cleared but engine still surges. If this sensor is disconnected, CEL comes ON, engine surging reappears.

It should read, "CEL comes ON, engine surging disappears".

Dave
 

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I gave up on the Denso 234-9001, bought and installed the $200 OEM Toyota 89467-35060 upstream A/F Sensor.

The truck now runs perfectly, I just finished a 210-mile trip with no problems.

Be it known that regardless of ads on Ebay, Amazon, and auto-parts stores, the Denso 234-9001 is NOT, I repeat is NOT a replacement for the OEM Toyota sensor p/n 89467-35060. I found out the hard way and have two brand-new spare Denso sensors to prove it.

Dave
Saugus
 
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