[pencil_&_paper]

Instead of paying $100 for Toyota to throw their scanner on my '96, I "rented" one from Canadian Tire. The code displayed P0141, and then I erased it, and presto!, the C.E.L. disappeared.

"P0141 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)"

Just wondering if anyone has anymore specifics about this. I do know that the center console heater for the back seats doesn't generate any heat, so I'm guessing the two issues might be related. Any help would be great.

As a side note, the Check Engine Light was the reason for getting a pretty good deal on the truck -the lady thought something was wrong with the engine, and didn't want to bring it into the shop.

[Nelsonmd]

Yeah, when you erase codes, the light disappears, that's how it works. The CEL will come back on if you don't fix it.

The O2 sensor heater circuit has nothing to do with the cabin heat. Likely you have a bad rear O2 sensor and need to replace it. No big deal, get it on Amazon, should be about $65.

BTW, you can get your codes read for free at most chain auto stores.

BTW, read the reference and documentation sticky at the top of the 3rd gen section here. You can get the FSM that will have the details on this code and all others, and there's a wealth of info there for newbies.

[techno]

This is an easy fix 99% of the time. That code means that an oxygen sensor in the engine exhaust system is telling the computer something that it shouldn't. There are two reasons why this can happen.
1. The sensor has malfunctioned
2. The ECM has malfunctioned. This usually does not happen.

There are two sensor on the exhaust pipe. They take measurements from the exhaust gases to help the computer to tune the engine properly. This sensor is located after the catalytic converter (the sensor furthest away from the engine). If you want to test the sensor you can, or you could just replace it, which is what I would recommend.

And fyi, the sensor contains an electrical circuit that heats the sensor to a specific temperature to ensure accurate reading. Hence the term 'heater circuit malfunction'.

[pencil_&_paper]

Originally Posted by techno

This is an easy fix 99% of the time. That code means that an oxygen sensor in the engine exhaust system is telling the computer something that it shouldn't. There are two reasons why this can happen.
1. The sensor has malfunctioned
2. The ECM has malfunctioned. This usually does not happen.

There are two sensor on the exhaust pipe. They take measurements from the exhaust gases to help the computer to tune the engine properly. This sensor is located after the catalytic converter (the sensor furthest away from the engine). If you want to test the sensor you can, or you could just replace it, which is what I would recommend.

And fyi, the sensor contains an electrical circuit that heats the sensor to a specific temperature to ensure accurate reading. Hence the term 'heater circuit malfunction'.

Very helpful, thanks a lot. I'll try replacing that sensor after I've checked for a proper electrical connection, and I'll read through the FSM to see what else I can find. I'll post my fix when it happens.

Cheers!

[pencil_&_paper]

I didn't want to replace only one Oxygen sensors, so I replaced both the 'upstream' and 'downstream' sensors. After installing both sensors, I started up the engine and in about 5-10 minutes the C.E.L. turned itself off. I also noticed an improvement in fuel consumption right away. Both Oxygen sensors came with gaskets as well.

I'll also be installing new Denso spark-plugs tomorrow, so I'm expecting a bit smoother idle too (no more pulsing). The old ones probably were not maintained either. Here were my costs and install times:

ROCKAUTO.COM -->Canada-->3 days delivery time (great prices!)

1. Denso Spark Plugs: 3194, $1.76 ea.

2. Denso Upstream Oxygen Sensor: 234-4161, $64.99 (30 min)

3. Denso Downstream Oxygen Sensor: 234-4153, $63.79 (30 min)

Thanks again for all the help. I'm learning lots as I go.

[highside74]

There is never a reason to replace both O2 sensors unless they are both bad and they very rarely go bad at the same time. It could have been years before your other O2 sensor failed. Now that it's done no big deal but this info is more for someone else that might be reading this thread. O2 sensors are either good or bad there is no in between so don't replace them until they fail.

[wildcatt]

Thx for these posts

I've got a 98 4runner - 3.6L and yesterday the first code I pulled was the P0141 01/02. I cleared it just so I wouldn't have to look at it.
Today - It came back and I scanned again - just to be sure. This time I've got P0141 01/02 and P0141P 02/02.

Does this mean I need to replace both sides of the downstream sensors? Or the up and downstream sensor on the same side

Which side is this? Drivers or passenger side?

thx

[TheDurk]

Originally Posted by wildcatt

Thx for these posts

I've got a 98 4runner - 3.6L and yesterday the first code I pulled was the P0141 01/02. I cleared it just so I wouldn't have to look at it.
Today - It came back and I scanned again - just to be sure. This time I've got P0141 01/02 and P0141P 02/02.

Does this mean I need to replace both sides of the downstream sensors? Or the up and downstream sensor on the same side

Which side is this? Drivers or passenger side?

thx

Do you HAVE both sides? The 3rd gen V6 has a common exhaust after the manifold and there is only Bank 1 on the passenger side. P0141 is the downstream (rear) sensor. There should only be ONE of those.

I don't know what that 02/02 refers to. There should be no Bank 2/Sensor 2 on your truck.

Unless major surgery has been done to provide a dual exhaust with two sensors, which I doubt.

[wildcatt]

Ok Thank you Durk - it's bone stock - so your probably right.

I haven't had a chance to look under as I'm at work. Sounds like I just need the 1 sensor then.

Cheers!

[matttremblay3]

I have a 1996 Toyota forerunner and I’m having a starting issue it starts when the engine is cold every time but when the engine warms up it doesn’t wanna start until the engine cools back down I changed the coils and spark plugs the only code that’s popping up is the O2 sensor I have a hard time believing that that’s what’s causing my issue any suggestions I was thinking about replacing the coolant temperature sensor


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[TheDurk]

Originally Posted by highside74

There is never a reason to replace both O2 sensors unless they are both bad and they very rarely go bad at the same time. It could have been years before your other O2 sensor failed. Now that it's done no big deal but this info is more for someone else that might be reading this thread. O2 sensors are either good or bad there is no in between so don't replace them until they fail.

This isn't true. They degrade slowly over time, as their speed of response diminishes. This is unimportant in the rear sensor, as its only purpose is to set codes, so no codes, no worry.

Front sensor is a different story. A degraded front sensor can result in degraded fuel economy and performance, without being so far gone that it sets a code. If the history of the front sensor is unknown, replacing it at the same time as the rear one is a reasonable decision, both to guarantee peak performance and provide a known age of part. If it's the salt belt, and the nuts are far gone, I'd call it a no-brainer.

For further reading:

http://4x4wire.com/toyota/4Runner/tech/O2_Sensor/

EDIT: Crap. I can't believe I just responded to a 2011 post. Oh, well, bad info going out for seven years still needed to be fixed.

[TheDurk]

Originally Posted by matttremblay3

I have a 1996 Toyota forerunner and I’m having a starting issue it starts when the engine is cold every time but when the engine warms up it doesn’t wanna start until the engine cools back down I changed the coils and spark plugs the only code that’s popping up is the O2 sensor I have a hard time believing that that’s what’s causing my issue any suggestions I was thinking about replacing the coolant temperature sensor


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You can get a pretty good idea if the ECT is working by hooking up a live scanner to the OBDII port. This issue can also be caused by fuel issues, including fuel pump and fuel pressure regulator. A good search will find you cases. Fuel pressure test may show the issue. But if the sensor is a front O2 sensor, I'd sure change that. Thing is. the front sensor does nothing when the engine is cold, and the ECM is in Open Loop at start-up. If the engine is hot, the ECM may be starting in closed loop with the funky front O2 the key player in the fuel/spark management system. Or, you may have forced the system to run in Open Loop full-time due to bad O2 sensor, and that can't be good for hot starting.

Why can't you believe that?

[Kamikaze6rr]

So, 00 limited 4wd and I change spark plugs, and fuel filter. I get engine light. Test and get heated o2sensor error bank 1 sensor 1 bank 1 sensor 2 error.
Replace the o2 sensors.
Clear codes. Drive almost 70 miles.
No code no cel. Turn off car and restart. Cel on
Wtf?

[brillo_76]

Originally Posted by Kamikaze6rr

So, 00 limited 4wd and I change spark plugs, and fuel filter. I get engine light. Test and get heated o2sensor error bank 1 sensor 1 bank 1 sensor 2 error.

Replace the o2 sensors.

Clear codes. Drive almost 70 miles.

No code no cel. Turn off car and restart. Cel on

Wtf?

How many miles? Plus what kind or parts did you use?

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[gamefreakgc]

Originally Posted by Kamikaze6rr

So, 00 limited 4wd and I change spark plugs, and fuel filter. I get engine light. Test and get heated o2sensor error bank 1 sensor 1 bank 1 sensor 2 error.
Replace the o2 sensors.
Clear codes. Drive almost 70 miles.
No code no cel. Turn off car and restart. Cel on
Wtf?

The actual codes helps.

If the CEL that just came on again is for the rear sensor and you already replaced both it usually means your catalytic converter has failed and needs to be replaced. That's if it's showing a P0420 code.