Lambda O2 sensor for RX400h, error code P0137/8

Clive-D · November 1, 2018

Hi all

I've had an ongoing electrics issue which has been resolved but the legacy is I need to replace the Lambda sensor...

The main code that comes up is P0138, O2 Sensor Circuit High Voltage Bank 1 Sensor 2. If I don't clear it for a day or so I also get P0137, same error but low voltage.

My car is 2008 so I don't think I will have the car for 10 years... so my question is, with prices varying from £30 on eBay to £70-150 at Eurocarparts, has anyone had experience and recommendations.

Cheers, Clive

The-Acre · November 1, 2018

I recently bought a cheap sensor for my wife's car (£25) and it lasted a day. I'm told, although I haven't looked, that there are many postings online about the problems with cheap O2 sensors.

Delphius1 · November 1, 2018

I agree, cheap O2 sensors can be a gamble. They don't last as long as better quality ones, but the thing you gave to remember the O2 sensor has failed for a reason. A sensor upstream can create fuelling issues, or oil being burned in the cylinders can cause the sensors to fail.

So if the O2 sensors fail, the underlying issue needs to be addressed as well as replacing the sensors, otherwise the new sensors fail quickly.

ColinBarber · November 2, 2018

I'd check the wiring / connectors / earthing / battery before replacing the sensor. If you can determine the sensor is at fault then get a Denso replacement - either Toyota/Lexus branded or just OEM Denso, as whilst the downstream sensors aren't as critical as the upstream air/fuel ratio sensors, cheaper ones do seem to trigger these types of errors.

Clive-D · November 3, 2018

Thanks for the advise - 'you get what you pay for' is a good rule generally. I'll ask my electrical fitter. I have had a problem resolved in another lengthy thread with all sorts of error codes being thrown up. Damaged wiring was found and replaced, this error is the only one that comes back, my chap said if it does it will need replacing. Hopefully this should sort it.

The-Acre · November 3, 2018

27 minutes ago, Clive-D said:

Thanks for the advise - 'you get what you pay for' is a good rule generally. I'll ask my electrical fitter. I have had a problem resolved in another lengthy thread with all sorts of error codes being thrown up. Damaged wiring was found and replaced, this error is the only one that comes back, my chap said if it does it will need replacing. Hopefully this should sort it.

Going back to my wife's car, and another issue. a few weeks ago she had an EML on with slight loss of power, this happened after a service and MOT. Another local garage read the codes of which there were 4, two relating to both o2 sensors. None of it made sense so we paid £65 to have it scanned by a very professional garage. After some time they traced the fault to a missing fuse, they replaced the fuse and all is fine! I still wonder what on earth happened during that service and MOT. No one seems to know!

Farnham Dave · June 11, 2019

On 11/1/2018 at 11:14 PM, Delphius1 said:

I agree, cheap O2 sensors can be a gamble. They don't last as long as better quality ones, but the thing you gave to remember the O2 sensor has failed for a reason. A sensor upstream can create fuelling issues, or oil being burned in the cylinders can cause the sensors to fail.

So if the O2 sensors fail, the underlying issue needs to be addressed as well as replacing the sensors, otherwise the new sensors fail quickly.

I have a failed lambda/O2 sensor (according to OBD2 fault code). Bank 1 sensor 2.

All was fine before I drove through some flooded sections of road yesterday.

I'm guessing (only guessing) that the sensor should be able to handle wet weather, so maybe it was on its way out anyway.

I reset the error codes, and the P0138 error code returns, so not just because it got wet (will have dried out?).

I've got the MOT test soon... Will get the garage to replace the sensor before the test.

Has anyone done or watched a replacement? I watched a YouTube video, and the procedure on the Toyota they were working on involved removing a seat and trim to get to the connector at the other end (wire passing through floor under seat). Is it just me, or is this a bonkers piece of design? You would think there would be a connector close to the sensor, or a more accessible route. Oh well, got to give the dealers a reason to charge a million squillion quid for replacing a simple sensor, I guess!

Herbie · June 11, 2019

31 minutes ago, Farnham Dave said:

I've got the MOT test soon... Will get the garage to replace the sensor before the test.

I'm not saying that you shouldn't get it replaced because they obviously do an important job, but there's no special rush or need to get it done for the MOT as hybrids are not tested on emissions.

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involved removing a seat and trim to get to the connector at the other end (wire passing through floor under seat). Is it just me, or is this a bonkers piece of design? You would think there would be a connector close to the sensor,

Connector technology has come a long way since the humble (and awful) Scotchlok, with heatshrink sleeving and even heatshrink solder sleeving and more. Would it really be so bad to leave the inaccessible 'real' connector in place under the carpets/seats or wherever and just cut the wires where they're easier to get at instead, as long as the proper sort of connector/enclosure was used?

Farnham Dave · June 11, 2019

It's tempting to snip and join isn't it?

So as long as an over rich fuel mixture isn't costing too much in petrol, and it doesn't do any damage, I'm free as a bird because it's a hybrid? That's just daft! Thanks for the info

Delphius1 · June 12, 2019

11 hours ago, Farnham Dave said:

I have a failed lambda/O2 sensor (according to OBD2 fault code). Bank 1 sensor 2.

All was fine before I drove through some flooded sections of road yesterday.

I'm guessing (only guessing) that the sensor should be able to handle wet weather, so maybe it was on its way out anyway.

I reset the error codes, and the P0138 error code returns, so not just because it got wet (will have dried out?).

I've got the MOT test soon... Will get the garage to replace the sensor before the test.

Has anyone done or watched a replacement? I watched a YouTube video, and the procedure on the Toyota they were working on involved removing a seat and trim to get to the connector at the other end (wire passing through floor under seat). Is it just me, or is this a bonkers piece of design? You would think there would be a connector close to the sensor, or a more accessible route. Oh well, got to give the dealers a reason to charge a million squillion quid for replacing a simple sensor, I guess!

If you drove quickly through large puddles, it can create enough water pressure to force water into all sorts of places it shouldn't be, like inside sensors. It can even strip wires from sensors. ABS sensors are the most vulnerable to water damage, but it's not uncommon for other sensors to be affected. It's worth getting under the car and doing a physical check of the wiring to the sensor to eliminate obvious repairable issues like a broken wire.

Many years ago I had a Ford Sierra 4x4 and drove through a large puddle. Water got into the intake and killed the MAF sensors. It affected the fuelling so badly you could see the fuel gauge dropping.....

Herbie · June 12, 2019

10 hours ago, Farnham Dave said:

So as long as an over rich fuel mixture isn't costing too much in petrol, and it doesn't do any damage, I'm free as a bird because it's a hybrid? That's just daft!

Initially you would think it's daft, because our engines pump out as much crud ans anyone else's when they're running - and therein lies the problem for the tester.

The engine in a hybrid isn't always running. Even when it's running it can't be revved up in neutral and held at a certain figure (think it's 2,500rpm for the high rev test) and even if it was running it may cut out halfway through the test, so they don't bother with it.

Lost it · June 14, 2019

But unfortunately, you will be storing up trouble for later on if you ignore the lambda sensors. As it will kill the cats eventually. And they are a "big ticket" item.

And it might not always be the case that the engine itself isn't checked for emissions.

Herbie · June 14, 2019

2 hours ago, Lost it said:

And it might not always be the case that the engine itself isn't checked for emissions.

How would that work then, given the info above?

Farnham Dave · June 14, 2019

On 6/11/2019 at 7:29 PM, Herbie said:

I'm not saying that you shouldn't get it replaced because they obviously do an important job, but there's no special rush or need to get it done for the MOT as hybrids are not tested on emissions.

Connector technology has come a long way since the humble (and awful) Scotchlok, with heatshrink sleeving and even heatshrink solder sleeving and more. Would it really be so bad to leave the inaccessible 'real' connector in place under the carpets/seats or wherever and just cut the wires where they're easier to get at instead, as long as the proper sort of connector/enclosure was used?

4 hours ago, Herbie said:

How would that work then, given the info above?

I asked my MOT test station, and they do check the emissions.

I'm going to get the sensor done anyway... Don't think I want to be running too rich for any length of time. As 'Lost it' pointed out... There's the cat to worry about. I also have memories of that classic chart in Haynes manuals with the pictures of spark plugs from cars suffering various defects (and I've not long had the spark plugs replaced).

Herbie · June 14, 2019

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I'm going to get the sensor done anyway... Don't think I want to be running too rich for any length of time

That's exactly why I started my post with the phrase "I'm not saying that you shouldn't get it replaced because they obviously do an important job" 😉

I just meant that if your MOT was imminent and you may struggle to get it done before the test, then there was no need to worry as it won't be tested anyway.

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I asked my MOT test station, and they do check the emissions.

I don't know if your MOT station are being too strict or mine too lax but mine don't test hybrids for emissions. In fact, I didn't know anything about it until they themselves told me that. Just double-checked with a different source and it looks like the former because hybrids are exempt from emissions tests:

And this brings up a whole new question now. If your MOT station does test for emissions even though they don't need to, what happens if it fails?

Would you just be able to say that the garage shouldn't have done it anyway, so the failure means nothing and the MOT as a whole is a pass? Or, will the failure stand and cause the whole MOT to fail, even though they didn't need to test in the first place?

And how is it even possible to test a hybrid for emissions when the running and revving of the petrol engine is not within their control?

Lost it · June 21, 2019

On 6/14/2019 at 5:14 PM, Herbie said:

How would that work then, given the info above?

Because the MOT test itself is still a "work in progress". And if we stay under the control of the EU it's only a matter of time until they decide we can only run our cars on the tears of red squirrels.

Point is still that running without working lambda sensors will kill the cats And if you are trying to "do the right thing" by running a Hybrid, it's a bit, well, silly to let the engine pollute every time it fires up. Unless you are only running a hybrid so you can brag about it.

Herbie · June 21, 2019

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Because the MOT test itself is still a "work in progress". And if we stay under the control of the EU it's only a matter of time until they decide we can only run our cars on the tears of red squirrels.

I meant how would it work given that the running and revving of the engine is not within the MOT testers control and the test is, I think, physically impossible?

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Point is still that running without working lambda sensors will kill the cats And if you are trying to "do the right thing" by running a Hybrid, it's a bit, well, silly to let the engine pollute every time it fires up. Unless you are only running a hybrid so you can brag about it.

Yes, I know that, which is why I started my reply to the OP with "I'm not saying that you shouldn't get it replaced because they obviously do an important job"
I just meant that if the test was iminent and he was pushed for time, there's no need to worry as it wouldn't be tested anyway and he could sort it at his leisure later.

Lost it · June 21, 2019

I suppose it depends on if it puts a "money light" up on the dashboard? Engine Management Light is now a major fail. It must come on with the ignition and then turn off when the engine is started. I know that this is a tricky one again, and I apologise for my lack of knowledge of the Hybrid ones, but the "Money light" would normally go off after a set period of time?

I dunno if I'm honest.

I know that during the last tranche of MOT updates there was talk of vehicles being plugged into the OBD2 port. And if there's a fault on the emissions system that would show whether the engine can be run or not as it would be a stored code.

However it didn't get through this time, doesn't mean they can't add it at any time, I think it was held off because of the cost of getting the equipment retro fitted at MOT stations in time for the new requirements.