Pre cat lambda sensor

[Paul. W]

Hi all,

Wondering if anyone can confirm my suspicions before I throw £££ into a new pre-cat sensor. Car in question is the Toledo 2.3 V5 AQN (170)

Getting two codes - P3211 and P0135 (O2 sensor heater circuit malfunction bank 1 sensor 1)

This points to the pre-cat sensor.

Now, over the past few days, the car has been running quite rough when cold. Three times now when approaching a set of lights for example, when dipping the clutch, the engine stalls with the red battery light illuminiated. Quick turn of the key and it instantly restarts and off I go. It also hesitates when accelerating, especially between 1500 and 2500rpm. Its also drinking fuel quite a bit.

Due to the battery light I thought it was the alternator voltage regulator. Tested with a multimeter tonight, and its pulling a perfect 14.2v upon load and acceleration. So that kinda rules that out. I guess the battery light illuminates when its stalled anyway?

I replaced the MAF two weeks ago (see my previous topic ) with a genuine Bosch MAF. No improvement at all.

Now this pre-cat sensor is around £100. After splasing out on a full powerflex polybush setup (front and rear!) im a little on a poorer side! From what I can gather, the pre-cat monitors the air/fuel ratio and tells the ECU to adjust the mixture accordingly. Why does this pre-cat sensor have a heater, and what does that achieve?

Replacing it - I have axle stands. Is this quite easy to locate and replace?

Ive cleared the codes tonight, however i'm sure they will be back after tomorrows commute.

 

[Paul. W]

Just to give everyone an update - I replaced the pre cat sensor and the car is now running great, AFTER an italian tune up All codes have disappeared.

Looks like that running it for a couple of weeks with the sensor knackered made it run rich for a while. Probably throw some new plugs in just to keep it sweet.

 

[damo :-)]

Glad its sorted fella, and thanks for the update.
Too many posts are made with no update about whether the problems are resolved.
Really annoying when you do a search for a cure and there's no final answers.
Enjoy the car
Regards.
Damo

 

[LukeK]

Is it easy to get to?

 

[Paul. W]

It is actually. You cant really miss it when your underneath. You could quite probably use a 22mm spanner to get it off without much getting in the way.

I didnt personally swap it out, I had it done whilst on the ramps getting the alignment sorted. It literally took 5 minutes, and the plug is in a plastic box nearby which simply unscrews also housing the post cat sensor plug.

What suprised both me and the mechanic is how long the bloody cable is attached to the sensor!

 

[LukeK]

Well that's good news then pal. Il give it a go. Cheers. How much did it set you back for the sensor?

 

[Paul. W]

I paid just shy of £100 for it from Eurocarparts however checking now they've got a 25% of code which knocks it down to £85. Can't link I'm afraid as I haven't done over 15 posts.

Use code websaver25

Don't think you'll fund it much cheaper! If your not in a rush then I suggest u do buy a lambda socket as well. Mine was quite easy to undo however if yours is a bit stubborn the socket will make it easier.

Its certainly not a cheap sensor

 

[LukeK]

Yeah I knew it wasn't going to be a cheap part. The last car I had the pre-cat sensor went too. Do you think it's worth giving it a clean to see if is just dusted up?

 

[damo :-)]

I paid just shy of £100 for it from Eurocarparts however checking now they've got a 25% of code which knocks it down to £85.

*cough* £75 *cough*

Damo

 

[Paul. W]

*cough* £75 *cough*

Damo

Its £115 on the website, I only had a 20% off code at the time

Yeah I knew it wasn't going to be a cheap part. The last car I had the pre-cat sensor went too. Do you think it's worth giving it a clean to see if is just dusted up?

Have you ran a code scanner to see what codes its pulling? If its like mine and showing a heater failure, I doubt cleaning it is going to make any difference. Noticed your from Preston, if your passing Warrington at all I'll happily run my scanner on your car.

I was going to show you the picture of my old one, but this post count isnt doing me any favours!

It is pretty coked up, the top is sealed onto the body so cant really pull it apart.

 

[damo :-)]

Its £115 on the website, I only had a 20% off code at the time

Let you off then

Damo