Toyota Yaris 1.33 (2009) - Engine management light. Different faults recorded | Technical matters | Back Room Forum

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Fri 10 May 2019 00:12

Toyota Yaris 1.33 (2009) - Engine management light. Different faults recorded - MartinDa

My TOYOTA Yaris 1.33 showed an engine management light. The garage diagnostic showed a fault on the o2 sensor 1 in bank 1. The garage replaced it. 20 miles later the light came on again. This time it recorded a fault on o2 sensor 2 in bank 1. The garage tested it and can’t see a fault with it. 5 visits to the garage and they can’t find the fault (which records in the diagnostics as a fault on either of the o2 sensors, record keeps changing between the 2).

I have noticed a pattern. The light regularly comes on after a local drive of 15 - 20 miles.
It never comes on during a shorter drive.
It does not come on during motorway driving, I drove over 100 miles on motorways at speeds between 50-70mph and no fault.

The fact that it comes on consistently at 15-20 miles of local driving made me think it was a temperature related fault ie when something warmed up but surely the fact that it doesn’t come on during a long motorway drive shows that to be wrong?

I thought it may be a Mass Airflow sensor fault but testing that voltage goes up on the live feed when I rev the engine so I can’t see that is the issue.

It has had a new air filter so that can’t be the issue.

The garage can’t find the fault on a diagnosis machine as it keeps recording 2 different faults (but a neighbours hand held fault reader gave a “low voltage on Airlfow sensor” reading once even though I can see voltage going up and down on my volt meter when I rev the engine. ). The garage never got that fault message on any of their diagnostics machine.

Someone suggested a loose or corroded wire but as the fault is so consistent at 15-20 miles local driving and never before that and because it never came on a motorway driving at speed I can’t see that being a wiring fault. It’s too consistent to my mind to be a loose or corroded wire.

Desperate and running out of ideas. Anyone help?

Edited by MartinDa on 10/05/2019 at 00:29

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Fri 10 May 2019 05:11

Toyota Yaris 1.33 (2009) - Engine management light. Different faults recorded - elekie&a/c doctor

Toyota engines can be very sensitive to sensors. Very often only genuine parts work correctly. What make sensors have been fitted?

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Fri 10 May 2019 07:50

Toyota Yaris 1.33 (2009) - Engine management light. Different faults recorded - MartinDa

I will check. In my mind I thought the fact that sometimes the diagnostics reports a fault on sensor one and other times it says it’s a fault on sensor two meant the fault was elsewhere?

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Sat 11 May 2019 00:25

Toyota Yaris 1.33 (2009) - Engine management light. Different faults recorded - phil_z70

elekie&a/c doctor is spot on

Sister in law had a very similar fault and it needed a new cat convertor

I don't think it was too expensive to replace, not 100% if a genuine cat was put on but genuine sensors were tried beforehand to confirm the problem

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Sat 11 May 2019 00:41

Toyota Yaris 1.33 (2009) - Engine management light. Different faults recorded - Big John

This is actually an older design of engine - for fault reporting there are broad spectrum O2 sensors. A common fail is the EGR valve which doesn not show up directly (no seperate sensors ) but confuses things downstream which then trigger errors such as seen in the original post. The same engine as fitted to the same age Auris is prone to this as well.

The reason it show up after 15+ miles is because on older petrol EGR designs this is when it kicks in (warmed up and cruising)

My old 2001 1.4 Octavia has a known EGR fault and after resetting eventually throws up a fault (insufficient flow in my case as monitoring better) after many miles but never around town. Likewise under a bit more stress on a motorway the fault doesn't show up.

Hope this helps - PS EGR is an easy fix on these engines

Edited by Big John on 11/05/2019 at 01:00

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Mon 13 May 2019 19:06

Toyota Yaris 1.33 (2009) - Engine management light. Different faults recorded - MartinDa

Thanks Big John, that would make sense of the fact that the light comes on consistently at 15-20 miles. Time to test out your solution. Fingers crossed and thank you again.

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Mon 13 May 2019 20:16

Toyota Yaris 1.33 (2009) - Engine management light. Different faults recorded - Big John

Good luck, and please report back how you get on

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Sat 25 May 2019 09:41

Toyota Yaris 1.33 (2009) - Engine management light. Different faults recorded - injection doc

I would agree with big john and eleckie AC

Garages get too wrapped up in reading fault codes.It needs diagnostic logic and experience to trace these silly faults. EGR most likely or an air leak. These are easily found by monitoring the airflow reading and taking an 02 reading in the exhaust. Trouble is lot of garages only ever seem to understand CO & HC whereas 02 & co2 are the best diagnostic tools, plus pattern parts on japanese cars are mostly a waste of time. Oxygen sensors being the biggest waste of time genuine only.

Information of what occurs when the light came on can be found in freeze frame data and more importantly fuel trims are a give away for fault finding.

The biggest problem is garages just dive in with their snap on, read a code replace a part and clear the fault codes, then you have lost the historic information as LTFT & STFT and freeze frame data and any pending codes.

A visit to a garage should be a first time fix rather than a guessing game !

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Sat 25 May 2019 11:12

Toyota Yaris 1.33 (2009) - Engine management light. Different faults recorded - John F

Garages get too wrapped up in reading fault codes.It needs diagnostic logic and experience to trace these silly faults........

......A visit to a garage should be a first time fix rather than a guessing game !

Quite so. A visit to U-tube helped me. Our 1.6 Zetec Focus EML started coming on last year, easily reset for a while by disconnecting the battery. I tried a U-tube solution of cleaning the edges of the butterfly valve in the throttle body (dirt build-up) which is designed precisely to not quite close off the air flow so the engine still gets enough air to idle. If there's not enough air, I suppose the engine management system will try to keep the engine running by injecting more petrol, resulting in a too rich mixture, presumably making the EML come on. So far the EML has stayed off, avoiding an expensive visit to the garage. Might be worth a try if your Toyota has a similar design.

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Thu 22 Jun 2023 05:25

Toyota Yaris 1.33 (2009) - Engine management light. Different faults recorded - Gos424

Hi MartinDa …. Realise its awhile ago, but our Yaris is doing exactly the same as yours did down to the last detail. Did you manage to solve the issue? How did you do it.

Many thanks in advance

Gos424

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