Engine warning light

[Yollander]

Help..... I have a 1999 1.0 VVT Yaris and the dashboard (Engine) symbol came on. I took it to a local guy who attached his plug-in diagnosis thingy and he said that it the fault indicated that it was "running rich". He didn't believe it was, so just got the light to go out. Any ideas?

[CTScott]

Did he reset the engine computer to clear the light or did he actually disconnect the light?

If he reset the computer, has the light come back on since?

[Crash]

Same light is also for changing the oil

[Yollander]

Thanks very much for those. He reset the engine computer and the light went out. We did a trip back to the UK (round trip of 1,000 miles) after having the car serviced oil & all filters changed (genuine Toyota parts) then last week, I left the car idling whilst I opened the gates and when I got back in the light was on again. I took it back to the same man and he re-set the car computer and the light has stayed off (touch wood). Again, he said he didn't think there was anything wrong, but he said it was the same fault indicating 'running rich'. Bit of a puzzle really.

[CTScott]

There are a few things that can cause a lean condition. Running lean is potentially very bad for the engine.

Here are a few of the things that can cause it on your 1.0L engine:

1. Injector blockage
2. Manifold absolute
pressure sensor
3. Engine coolant
temperature sensor
4. Fuel pressure
5. Gas leakage from
exhaust system
6. Open or short in
heated oxygen sensor
circuit
7. Heated oxygen sensor

[Yollander]

Thanks CT very comprehensive. You put "Running Lean" did you mean that or was it a typpinng error? The guy told me that the fault indicator was "Running Rich".

I have a Haines Manual and it is quite good but it is a bit complex for me.

The car runs normally (quite good for over 120,000 miles) and seems fine. She is a bit 'smelly' (of fuel) when I start her up on very cold mornings but I guessed that was something like an automatic choke, but soon returns to normal when warmed up. Interestingly, I had the French equivelent of the MOT Test (which is quite strict), done in November and there was no problems with emissons, passed with flying colours.

[CTScott]

Thanks CT very comprehensive. You put "Running Lean" did you mean that or was it a typpinng error? The guy told me that the fault indicator was "Running Rich".

I have a Haines Manual and it is quite good but it is a bit complex for me.

The car runs normally (quite good for over 120,000 miles) and seems fine. She is a bit 'smelly' (of fuel) when I start her up on very cold mornings but I guessed that was something like an automatic choke, but soon returns to normal when warmed up. Interestingly, I had the French equivelent of the MOT Test (which is quite strict), done in November and there was no problems with emissons, passed with flying colours.


I misread the initial post. Occasionally Running rich is less bad for the engine. Frequently running rich will cause problems with the emissions systems.

All of the same potential causes of running rich are the same as the list I posted above (except for rich there's too much fuel for the amount of air as opposed to too much air for the amount of fuel for lean).

[Bluevitz-rs]

How old are your spark plugs? It's also possible you have a bad O2 sensor.

[Yollander]

Spark plugs are about 2 years old so will change them this week. O2 sensor could be at fault but it is very random.

[Zaphod]

Spark plugs are about 2 years old so will change them this week. O2 sensor could be at fault but it is very random.
I had a similar problem with my TJ about 8 years into it, the symptoms were very random as well, the light would be on and off for a while, and then it was just on and running rough. The O2 sensor and was relatively cheap and very easy to replace on the Jeep, in fact it took longer to diagnose the problem and buy the part than to replace it.

Hope yours turns out to be the same.