help anyone - Error Code P0141

[ChrisGB]

at the moment i have a 15ohm 10watt resistor fitted and i'm still getting a CEL, so it doesn't always work

Oh   s:( s:(   I'll be trying that at the weekend. Fingers crossed   s:? :? s:?   Lucky I bought a OBD-II reader. Could prove very useful.

Sorry to resurrect this old thread

Did anyone try the 25 / 27 ish Ohm resistor? Reading this thread it would appear that fitting a 15 Ohm resistor would leave the ECU feeding current continually to the resistor and it will probably still throw CELs, fitting a higher resistance would also potentially throw them if the heater does not draw enough current.

As for power ratings, assuming 12V heater circuit the 15 Ohm resistor would be sinking 9.6W, so fitting a 10 is marginal, a 50W would be better from a peace of mind perspective. If 25 Ohm, then less than 6W, so a 10 would be OK.

Edit: Just found these:

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0157566

What do we reckon?

Chris

[Anonymous]

Peter, Stock heater is 14 ohm give or take

Is that hot or cold?  The resistance is unlikely to be constant.

This is exactly what happened to me. Went to custom install my flowmaster 80 Series, and CEL lit up. I was convinced that the shop messed it up, but now I feel better about it. I was worried the first couple of days with the light. But it went away.....( the paranoia ), not the light.

[trickyD]

I'm a little shocked that no-one has diagnosed this one properly yet, its got to be one of the most common Engine managment faults on this car...

Basically, Dont panic... This really isnt a problem...

The P0141 code is an advisory code, it has no effect on the actual running of the engine. Here, for the beneift of anyone who may happen to find the search button in the future, is why...

The code refers to what we call the 3rd O2 sensor, but is more accuratley called bank 1, sensor 2. There are 2 other O2 sensors on the engien, known as Bank 1, Sensor 1, & Bank2, Sensor 1. These 2 are responsible for measuring the fuel air mix that has just been burnt and exhausted by the engine. There are 2 of them because Toyota's ECU actually runs this engine as 2 seperate entities, i.e. it treats it as 2 two cylinder engines. Wierd, but effective.

The 3rd O2 sensor is fitted downstream of all the cats, wheras the 2 metering O2 sensors are fitted upstream so that they can measure the raw, un-catalysed gas coming out of the engine. Its only job in life is to measure the O2 content of the exhaust gas after the cats. The ECU then compares this reading to the one it took from the Bank 1 sensor in the manifold.  The logic it then applies to the 2 readings is astoinishingly simple:

If the 2 readings are different, and more importantly the reading from the  3rd O2 sensor is more stable than that on the manifold O2 sensor, then all is well with the world. It means that the ECU knows your cats are working as they hasve changed the make up of the gas.

If the 2 readings are the same, then the ECU knows that the cats are doing nothing to the gas at all, and lights the CEL, which prompts you do go and have your wallet lightened by your local dealer...

Becasue theres no effect on the closed loop control of the Fuelling, the engine managment makes no changes tht would effect power, or economy.

You dont actually have a failed O2 sensor though, I'd bet good money that if I hooked up my OBDII reader to your car, I'd see sensible readings coming from the 3rd O2. what you actually have, is a failed heater element.

Each O2 sensor has a built in heater inside it. The heaters are used to get the Zirconia mesuring sensors inside them up to operating temperature quickly so that they can get on with the job of measuring oxygen. This gains vital seconds in the process of gaining efficient emissions control on a cold start of the engine. Once the engine is hot, clearly anything in the exhaust flow is'nt going to be in need of heaters! The ECU monitors these heaters by measuring the current going to them, to much or too little flags up the fault code you have at the moment. The sensor itself is still working, it just takes a while to warm up... Again, having a duff heater in an ptherwise functional 3rd O2 sensor wont cause any problems with engine managment.

So, what to do to fix it? Well, you can replace the unit, or you can ignore it... Either way your car will go just as fast as its always done, using exactly the same amount of fuel. The problem with just leaving it, is that with the engine light already lit, you wont see any new problems should they occur. Fixing the thing is expensive, especially considering all you are going to gain is clear dashboard.

I appplied a bit of electrical tom-foolery to mine when it went, I simply connected a high power resistor to the heater circuit on the sensor, so that it drew the "correct" amount of current from the ECU, That way ,as  far as the ECU was concerned, the heater was working, and after 2 full start -warm up - drive -stop- cool down cycles of the engine, the light goes out. Simple...

Best Internet forum post ever!
  s:bowdown: :bowdown: s:bowdown:

[GSB]

Best Internet forum post ever!
  s:bowdown: :bowdown: s:bowdown:

Glad you liked it.  s:wink: :wink: s:wink:  

It's always nice to see people still find use for all the crap I used to write on here!

Whilst rooting through my old tool cabinet the other day, I came across a pile of old MR2 bits. An air intake system, a new OEM exhaust manifold, and a handful of the high power resistors I used to defeat the heater circuit check function on the 3rd Oxygen sensor.

Anybody wants a free resistor for their car, drop me a PM...

[loadswine]

That's brilliant, still helping people out on here after all these years. Ace stuff Grant!  s:) s:)

[trickyD]

This is what the Internet /should/ be about...

Sharing information and (occasionally) high powered resistors  s;) s;)

Thanks dude

[GSB]

Why thank you...  s:wink: :wink: s:wink:  

Yes, I still wander though these forums from time to time, seeing just how these little cars are holding up after almost 14 years, wondering if I should buy a cheap one and turbo the knackers off it for a bit fun, and if Toyota will ever pull their finger out and build a 4th generation so i can have one with a warranty. Thing is, these Mk3's seem to be becoming a rare sight these days, shame...

[chriswales]

Mine went recently..it was the o2 sensor after the cat. Not difficult to get to, but an absolute pig to get off. I had to resort to getting one of the guys in my locat garage to apply some gentle heat!! The o2 sensor was about 85 quid from euro car parts