Yaris Engine Light Woes - Help Needed

dangermouse425

dangermouse425

dangermouse425

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My girlfriend's 2003 1.3 Yaris' has a fault. The engine light has come on and won't go away, despite being reset about six times. The light came on shortly after an MOT and Service. The garage said the error code might have something to do with the catalytic converter, but they also said it couldn't be that because it wouldn't have passed the MOT if the catalytic converter was broken.

Several garages have looked at it, and none can find anything wrong with the car. Every time a garage rests it, the light comes back on some time after.

Last week a Toyota dealer reset it after:

- oil change
- new air filter
- new spark plugs
- brake fluid change

But the light came back on a few hours later.

The light comes back on between 2 hrs and 3 weeks after a reset, but it always returns.

Any suggestions? What could it be?
 
Are they actually reading the codes or just resetting the light?

Some places just use a generic code reader not something that reads live data.
 
The place that originally did the MOT said they read the code and they said it "was related to the catalytic converter".

I'm not sure what they read it with, but it has been taken to a Toyota main dealer too who can't work out what it is.
 
Exactly the same happened to my mum's Yaris shortly after we bought it - the garage where we purchased it and Toyota couldn't work out why until a few weeks later something failed in her auto transmission. Luckily it was still under warranty with the garage that she bought it from.
 
dangermouse425 said:
The place that originally did the MOT said they read the code and they said it "was related to the catalytic converter".
Click to expand...

Sounds very vague to me! I'd be wanting the actual code. If it's just an emissions related code and they're just assuming the cat, then they could be way off the mark!
 
Need the actual code first.
Maybe purchase a cheap code reader, plenty of people that can walk you through what to look at on the live data for extra help.

The bluepoint/snap-on/microscan one has been mentioned on here before and I'd heartily recommend it too.
http://bit.ly/NeY50G
 
You really need the code to start diagnosing the fault. Resetting the codes is never going to keep the MIL light out if the underlying fault has not been fixed.

It's also quite possible for a cat related error code to be thrown and still have the car pass the emissions test, which suggests the garage you have taken it to have arse/elbow identification problems.
 
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Haven't tried reading it myself as I left my OBD at home and she asked me yesterday to post on "that car forum you're always reading". I'm hoping to get the fault code this afternoon and investigate it further.

It genuinely sounds like all the garages she's taken it to are being a bit useless.
 
OBD reader says it's as follows:

Fault Code: [P0420]
Catalyst System Efficiency Below Threshold (Bank 1)

Looking on the net it seems this could be either a dodgy sensor (£100ish) or a new cat required (£1000+). Since the MOT emissions test was fine and bearing in mind the value of the car, what do you recommend she does?

Bearing in mind the light originally came on shortly after a garage services and MOT'd the vehicle, do you think it's likely they may have damaged the cat/exhaust system whilst working on the car?
 
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Hold fire on those thoughts and going straight to Internet searches.

Now use the live data and see what the secondary lambda sensor is actually doing when the car is fully warm and at idle or fast idle.
Unlike sensor 1 which should oscillate between 0.2v and 0.8v
Your sensor 2 should hold around 0.6v.
If it oscillates similar to sensor 1 then cat is FUBAR.
If you are getting something like 0.3 v and not moving at all then sensor probably FUBAR.
I'd also back up your findings with gas test from a non MOT Garage, somewhere with a "five gas analyser" and get them to explain the readings.
A good cat should hold 15% Co2

*Edit as I dun made a boo boo on gas readings.
 
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The above is how I would go about sorting this too - It's definitely worth having the emissions checked again as i've had a similar problem before (on a toyota funnily enough). My MR2 needed both a cat and a lamda as it turned out, I was likely just unlucky (or uncovered the problem with the cat by removing the pre-cat) but don't discard the possibility.
 
I had the same error on my MG ZS 1.6 the other day, used Torque on my phone to look at the sensor readings and the sensor second sensor is showing -99 as the reading so its probably just confused. £60 for a new one is too much at the moment so I just reset it :p
 
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