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Previa Engine Management Warning Light, Urgent.

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Instructions

Turn the engine on and allow it to idle for two to five minutes, then turn the ignition key off. Raising the temperature of the exhaust system will make removing the sensor's retaining nuts easier as the metal expands.

Raise the Previa with a jack, then lower it onto safety stands to increase the workspace.

Wear heat-resistant gloves, then climb underneath the Previa and locate the oxygen sensors. There are two sensors. Both sensors are located on top of the exhaust pipe. One sensor is located in front of the catalytic converter, and one sensor is located behind the catalytic converter.

Trace the wire located at the top of each sensor to each wire's electrical connection, then unplug both wires from their connections.

Remove the two nuts that secure each sensor in place against the exhaust pipe with a wrench, then lift the sensors out of the exhaust pipe and discard the old gaskets.

Position new gaskets onto the bottom of each sensor, then position the sensors on top of the exhaust pipe.

Tighten each sensor's two nuts to 14 foot-pounds of torque with a torque wrench.

Plug each sensor's wire into its respective wiring connection.

Lower the Previa to the ground with the jack.

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Just to give an update I unplugged the sensor from the main connections and cleaned it out. The light stayed off for a good week apbut now it has come on again. I've been doing some research and the sensor is the first one on the right hand side at the top of the manifold. Correct me if I'm wrong. But when I unplugged to see if thTbwas the sensor I got the following message on my maxiscan.

P0031

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To fix a P0031 DTC code, you'll need to do a proper diagnosis. To do that, you'll want to inspect the wiring and connectors leading to the sensor.

Also if equipped with a heater relay and fuse, you'll want to check those as well. Use a digital volt ohm meter to:

•check for 12 volts at the heater circuit feed (hint: unplug the sensor and check at the wiring connector to do this measurement)

•check the ground circuit for continuity

•measure the resistance of the heater circuit (done on the sensor itself)

•measure the resistance and voltage of the wiring

Refer to a service manual for the correct specifications (volts, ohms) for your vehicle. On some Toyota vehicles this code is triggered when the resistance of the heater circuit is below 0.8 A.

With that said, a common fix for this DTC is to replace the air/fuel (O2 oxygen) sensor #1 on bank 1.

Please keep in mind that OEM (original equipment) replacement sensors are recommended (from the dealer). Aftermarket sensors can be less reliable and of poorer quality (not always, but more often).

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Mobeyone, I bought the Previa at 80,000 miles because my previous experience of Toyotas is, like you say, that they're built like tanks. I bought it from a local second hand car dealership, with a warranty, but not a FSH. In fact, there was very little SH which should have set the alarm bells ringing really.

As stated in my previous post, they changed a faulty lambda sensor over for me last week, but the emwl is back on now . . . Grrr! The dealership is doing some work on it under warranty but i suspect they are doing it on the cheap and I am starting to wonder whether i would be better off taking it to a Toyo dealership to see if they can get to the bottom of it. Alternatively i could just invest in some sticky black tape and tape up the faulty sensors. Seems like others eventually went down this route.

Peter

PS thanks for the good mpg-calculator tool.

Hi there. When you say tape,it up, what do you mean? Thanks.

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InstructionsTurn the engine on and allow it to idle for two to five minutes, then turn the ignition key off. Raising the temperature of the exhaust system will make removing the sensor's retaining nuts easier as the metal expands.Raise the Previa with a jack, then lower it onto safety stands to increase the workspace.Wear heat-resistant gloves, then climb underneath the Previa and locate the oxygen sensors. There are two sensors. Both sensors are located on top of the exhaust pipe. One sensor is located in front of the catalytic converter, and one sensor is located behind the catalytic converter.Trace the wire located at the top of each sensor to each wire's electrical connection, then unplug both wires from their connections.Remove the two nuts that secure each sensor in place against the exhaust pipe with a wrench, then lift the sensors out of the exhaust pipe and discard the old gaskets.Position new gaskets onto the bottom of each sensor, then position the sensors on top of the exhaust pipe.Tighten each sensor's two nuts to 14 foot-pounds of torque with a torque wrench.Plug each sensor's wire into its respective wiring connection.Lower the Previa to the ground with the jack.

Hi raistlin. Thanks for that info. Let me give some background about the car. I purchased the car a few months ago from brother-in-law as his wife insisted the car is a dream to drive. With children growing up we needed a bigger car than the Zafira. So we went ahead with the purchase. After a few days we noticed Oil drips on the driveway and looking down under the car I noticed oild from the sump plug. We'll I bought a new sump plug with washer and we fixed that problem for about £5. After driving a bit I heard that the exhaust was making some loud sound. I looked under and guess what. The exhaust had split. So I bought an after market one for about £70 and fitted this in myself. I used a special exhaust paste which I believe help it to seal. The next day I then had this mil show up the first time ever. I spoke to my brother in law and he advised that when the engine was rebuilt a few years the only light to show up we're about the nox sensor which then settled down after driving for sometime.

My feeling is that the after market exhaust must be the culprit. If not that then perhaps it is the way I fitted this in. I think that perhaps I applied too much of that exhaust paste that somehow there must a small blockage from the inside. See the pictures if the exhaust as it is now.

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And now this is the join where I think too much pasts is applied.

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Yes that may be your problem

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On a good sunny day I plan to disassemble the rear silencer (sorry not exhaust) and then give it a good clean. I think I will need to scrape off all that exhaust paste and then give a good clean.

In my first attempt I applied the paste both inside and outside. Do you think that joining the silencer with the centre exhaust and then applying a small amount of exhaust paste on the outside might be better?

My feeling is that this must be setting off that sensor and hence the mil light. Hopefully I will report back once a get this done.

Astro

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Sounds like a plan

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We'll it seems that yahoo mail has put these replies into my junk mail. Not very helpful to me.

Anyway I have taken off the rear silencer (exhaust) and cleaned out the connections. I'll put a YouTube link here for anyone to check out.

And yes after a day I got the dreaded engine light show up again. Haven't yet checked what code it is but I suspect it's the same p2238 code.

But the very next day after that the engine light has disappeared. This seems to be happening quite a lot. The engine light will come and then go off by itself. So far it's off for the moment.

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InstructionsTurn the engine on and allow it to idle for two to five minutes, then turn the ignition key off. Raising the temperature of the exhaust system will make removing the sensor's retaining nuts easier as the metal expands.Raise the Previa with a jack, then lower it onto safety stands to increase the workspace.Wear heat-resistant gloves, then climb underneath the Previa and locate the oxygen sensors. There are two sensors. Both sensors are located on top of the exhaust pipe. One sensor is located in front of the catalytic converter, and one sensor is located behind the catalytic converter.Trace the wire located at the top of each sensor to each wire's electrical connection, then unplug both wires from their connections.Remove the two nuts that secure each sensor in place against the exhaust pipe with a wrench, then lift the sensors out of the exhaust pipe and discard the old gaskets.Position new gaskets onto the bottom of each sensor, then position the sensors on top of the exhaust pipe.Tighten each sensor's two nuts to 14 foot-pounds of torque with a torque wrench.Plug each sensor's wire into its respective wiring connection.Lower the Previa to the ground with the jack.

Ok it looks as though I'll be giving this method a go. But only when the weather is nice for me to go out.

But before I do I think I'll give the centre exhaust I go look over. Just to make sure there are no cracks where emissions could be escaping and outside air coming in. This could also trigger a sensor so I was told.

I like the idea of renewing the gaskets. Makes a lot of sense. But this is certainly a lot more work involved and I was hoping to avoid this.

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We'll it seems that yahoo mail has put these replies into my junk mail. Not very helpful to me.

Anyway I have taken off the rear silencer (exhaust) and cleaned out the connections. I'll put a YouTube link here for anyone to check out.

And yes after a day I got the dreaded engine light show up again. Haven't yet checked what code it is but I suspect it's the same p2238 code.

But the very next day after that the engine light has disappeared. This seems to be happening quite a lot. The engine light will come and then go off by itself. So far it's off for the moment.

Hi Astroscope,

After reading your issue and seeing the video, I would have got a new gasket. I recently changed the complete exhaust system on the Avensis, and this included new gasket seals. The system was aftermarket - less than £145, but once fitted properly ( I had to re adjust the connections), all was okay.

Two things to note - I was advised to not to use joining paste, the seals do the work. It is easy when using new exhaust system. Secondly that drip on the joint means it is not sealed tight. That is the why I adjusted the exhaust. It will carbon up later but I wanted done properly. I don't think the replacement exhaust or paste cause the EML light to come on.

It seems to be common on Toyota engines to have a pre - cat sensor fault code. My friend has an Avensis vvti with the same problem.

Good luck on the fix.

Konrad

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I am having the same problem with my Previa D4D T Spirit 2006,-----the EML has shown a couple of times,not worried about the light but am very concerned by the fact that when the light shows up on the dash the engine cuts out,this is an incredibly dangerous scenario,as luck would have it,both times it has ocurred I have been on a quiet country road but what happens if I am in the outside lane on the M25 or similar and the light shows,the engine cuts and I am without power steering, brakes and engine power,it is a potentially deadly situation.I contacted Toyota GB to advise them of this,they said I should take the vehicle to my nearest Toyota agent for investigation but as live in the south of France it may not be very easy to explain the exact problem re loss of power,I will of course make a visit to them but first I posed the question to Toyota GB,---is the ECU designed to cut the engine when this EML light shows on the dash,---if so it is an incredibly poor and dangerous piece of design or could it be is that the electrical circuit up to the dashboard light is faulty and short circuiting the ECU causing the engine to die.

Has any one else experienced this very dangerous situation,----the light coming on is comparatively inconsequential, a dead engine is however very serious. and needs highlighting via motoring organisations.

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I am having the same problem with my Previa D4D T Spirit 2006,-----the EML has shown a couple of times,not worried about the light but am very concerned by the fact that when the light shows up on the dash the engine cuts out,this is an incredibly dangerous scenario,as luck would have it,both times it has ocurred I have been on a quiet country road but what happens if I am in the outside lane on the M25 or similar and the light shows,the engine cuts and I am without power steering, brakes and engine power,it is a potentially deadly situation.I contacted Toyota GB to advise them of this,they said I should take the vehicle to my nearest Toyota agent for investigation but as live in the south of France it may not be very easy to explain the exact problem re loss of power,I will of course make a visit to them but first I posed the question to Toyota GB,---is the ECU designed to cut the engine when this EML light shows on the dash,---if so it is an incredibly poor and dangerous piece of design or could it be is that the electrical circuit up to the dashboard light is faulty and short circuiting the ECU causing the engine to die.

Has any one else experienced this very dangerous situation,----the light coming on is comparatively inconsequential, a dead engine is however very serious. and needs highlighting via motoring organisations.

I don;t think the engine should just cut out like that. Have a computer hooked asap. It might be a sensor issue.

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So far I can say that the engine light has not come on. Although I do plan to at some point replace the 02 sensor. Will set me back around £80 but looking at where it is located near the engine, the job should be doable by the casual DIY person.

Astro

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Astro,

I can't really imagine that engine failure would be 'designed in' when the light shows, but what I'm trying to establish is whether you, or any other member,has experienced something similar,if so the problem should be taken away from Toyota and advertised to as many motoring organisations as possible for investigation as it could be a serious road safety issue,

thanks anyway.Tony Holland.

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Well the very worst of all situations occurred today,the one I've been dreading concerning the engine management light.

I had just crossed the border into Spain on the A63,in the outside lane of a two lane motorway with major road widening underway and no hard shoulder,with the arnco barrier next to the inside lane I was overtaking a lorry when the EML came up and as previously explained,on my vehicle the engine completely cuts out when this light comes on.

It was an extremely dangerous and bum twitching thing to happen,dead engine on the outside lane and a heavy lorry between me and the slow lane I hit the hazard lights and the following traffic all slammed their anchors on and i was able to cut inside after the lorry had finished 'undertaking me',nearly literally,luckily there was a gap in traffic after the lorry passed,there was a slight downward incline so I was able to coast (on the inside lane) to a slip road just ahead,when I had stopped the engine immediately fired up again and I was able to continue and make the return journey with the light on,which is when it is in the 'safe mode',hoping against hope that it would stay lit.

Surely someone on the forum with a D4D engine has experienced this dead engine scenario after the EML lights up,with all the chatter that gone on about the dreaded light showing I can't be the only one to experience a near death situation because of it,

I am going to contact Motoring Which and anyone else you will listen as this is a potentially lethal fault and someone else might not be so lucky as I was.

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Astro,

I can't really imagine that engine failure would be 'designed in' when the light shows, but what I'm trying to establish is whether you, or any other member,has experienced something similar,if so the problem should be taken away from Toyota and advertised to as many motoring organisations as possible for investigation as it could be a serious road safety issue,

thanks anyway.Tony Holland.

No. I don't think the engine should just cut out like that. It's very dangerous. I would stop driving it and get it checked. Thank almighty God god that at least your ok.

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If you have access to a scanner plug it in the OBD2 socket and check for any engine management codes. It might give you a clue as to wear the problem might be.

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Astro,

Many thanks for your reply and good wishes,--yes I think somebody,or something was looking out for me on Thursday,---I won't be using the car again until I can get a definitive diagnosis, currently the vehicle is an unpredictable death trap,and I will be chasing Toyota every way I can to explain this potentially lethal fault in one of their products,perhaps the Toyota Club would be willing to put their muscle behind my efforts, it could after all be an inherent fault waiting to happen in any model,as I said before,its not the light coming on that is a problem,I don't expect help in diagnosing the reason for it showing but I do expect urgent help in making the vehicle safe for me and other road users, in the meantime i will be wheeling out the old Rover 75.

Many thanks Tony Holland

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Further to previous post,took vehicle in to our local auto electrician,he is top notch,he accessed the fault codes from information on the 'carte gris' (french log book) and it threw up a fault with the turbo, small leak in a pipe ? which he fixed,84 euros,certainly feels livelier but I still have this uneasy feeling about when the 'next' fault may occur and 'kill' the engine.Surely their is some computer geek on the clubsite who would know how to allow the EML to light up but programme out the instruction which kills, or sends the engine into limp mode,after all,I've managed for most of my motoring life in all types of vehicles without a 'safety' feature which kills the engine,surely the light showing is enough to alert anyone that there is a fault that needs attention.

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I have a 2002 previa, petrol with a manual gearbox. It was purchased just over 5 years ago, and the EML came on during the trip home.  After checking, it was found to have P0420 and P0430 errors. One sensor was replaced, and 20 miles down the road the lifht came back on. Had a second sensor replaced,  and it came back on again. Reading this thread, it would seem it needs an updated cat, but as I have had 5 mot's done, and its passed the emissions test with flying colours, I think its time to buy a roll of blsck tape 😂

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Have you had an obd scanner read for any faults lately, if the car is a 2.4 petrol there are four 02 sensors on the engine. I'd get it checked first, warning lights showing will fail an mot.

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