O 2 Sensor at Cat Box 'Kaput'

[Mxchen118]

Hi All, can shed some background of the main function of the above. My failed yesterday after hitting an object on the road and damage the wiring to the sensor . My Dashboard console yellow alert light came on. Engine running still normal, not sure what the impact in the long run, fuel consumption, inspection or exhaust CO2 ?

Casper

[Watwheels]

The purpose of an O2 sensor at the exhaust is to feedback the amount of unburnt air to the engine management ecu. It will dan either add more air or add more fuel to the mixture for combustion according to the feedback. You may experience your car suddenly move very slowly cos no air feedback the ecu will input little air & fuel. You step paddle to the metal also no response, it'll just crawl.

 

The damage could be the engines internals on the long run cos the air/fuel mixture could be too lean or too rich.

[Teriyaki]

how come can hit something? its supposed to be in the bonnet..?

 

o2 sensor is really very troublesome. mine spoilt.. life with it till sell car.

[Kyojin]

The purpose of an O2 sensor at the exhaust is to feedback the amount of unburnt air to the engine management ecu. It will dan either add more air or add more fuel to the mixture for combustion according to the feedback. You may experience your car suddenly move very slowly cos no air feedback the ecu will input little air & fuel. You step paddle to the metal also no response, it'll just crawl.

 

The damage could be the engines internals on the long run cos the air/fuel mixture could be too lean or too rich.

 

sorry, but it seems you are totally off-topic here. you are talking about the pre-cat O2 sensor. when this sensor is damaged/removed, the ECU will go into "limp home" mode in semi-closed loop mode. the ECU will approximate the amount of fuel based on other input. this is self-preservation mode to prevent engine damage.

 

more accurately, what the thread-starter is experience is the loss of the post-cat O2 sensor. this is to measure the efficiency of the catalytic converter, nothing more. it provides feedback to the ECU, which will measure both the pre-cat and post-cat voltages to see if there's a difference in A/F ratio. if there's a discrepancy, the ECU will "think" that there's a fault with the cat converter. if the ECU detects that the post-cat O2 sensor is missing/malfunctioning, it will automatically throw a Malfunction Indication Light (MIL) or Check Engine Light (CEL). however, this usually doesn't affect normal mechanical operation of the vehicle.

 

to answer the thread-starter's question. the impact is none - you get an irritating warning light, and the loss of ability to monitor the efficiency of your cat converter. that said, frayed/dangling loose wires are a recipe for disasters - best to get that fixed.

[Legan]

Read that if you have some technical knowhow, can switch to aftermarket ones which would cost less. Not sure if mechanics in Singapore know how to switch to other brands though

[Mxchen118]

5th Gear, thx for the input, guess that is the most likely scenario in my case. the wiring to the plug light sensor to the cat box was severe by a flying object that flew up to my cat box while I was driving, light on dashboard console came on. On checking with the mech at garage, he try to connect back the wiring but light did not go away. Anyway, fill up my gas tank and now montoring the comsumption . A/F ratio feedback to the ECU without the )2 sensor, wonder whether the manufactor will it have a default number when it' Conk out'

Casper

[Hamburger]

sorry, but it seems you are totally off-topic here. you are talking about the pre-cat O2 sensor. when this sensor is damaged/removed, the ECU will go into "limp home" mode in semi-closed loop mode. the ECU will approximate the amount of fuel based on other input. this is self-preservation mode to prevent engine damage.

 

more accurately, what the thread-starter is experience is the loss of the post-cat O2 sensor. this is to measure the efficiency of the catalytic converter, nothing more. it provides feedback to the ECU, which will measure both the pre-cat and post-cat voltages to see if there's a difference in A/F ratio. if there's a discrepancy, the ECU will "think" that there's a fault with the cat converter. if the ECU detects that the post-cat O2 sensor is missing/malfunctioning, it will automatically throw a Malfunction Indication Light (MIL) or Check Engine Light (CEL). however, this usually doesn't affect normal mechanical operation of the vehicle.

 

to answer the thread-starter's question. the impact is none - you get an irritating warning light, and the loss of ability to monitor the efficiency of your cat converter. that said, frayed/dangling loose wires are a recipe for disasters - best to get that fixed.

yo bro, to summarize up on ur write out-

1. pre cat lambda spoilt- get worry

2. post cat lambda spoilt- live wif it.

 

Correct???

 

Btw, can we say if e pre cat lambda is kaput, most of e time e A/F mixture is tune richer by ECU, to safe guard e engine??

Edited March 21, 2009 by Hamburger

[Try_conti]

for cars with one lambda sensor (mine is EU2 compliant only), would it be pre or post-cat ? I presume pre-cat ?

[Kb27]

If it's just wiring damage, wouldn't be it as simple as just joining the wires back?

 

My burst tyre damage the ABS cable and light up on the dashboard.

I just solder the wire back in place and it's fixed.

[Kyojin]

5th Gear, thx for the input, guess that is the most likely scenario in my case. the wiring to the plug light sensor to the cat box was severe by a flying object that flew up to my cat box while I was driving, light on dashboard console came on. On checking with the mech at garage, he try to connect back the wiring but light did not go away. Anyway, fill up my gas tank and now montoring the comsumption . A/F ratio feedback to the ECU without the )2 sensor, wonder whether the manufactor will it have a default number when it' Conk out'

Casper

 

the check engine light has to be reset either via:

- OBD2 tool/scanner

- disconnecting your battery for about a minute

 

 

[Kyojin]

yo bro, to summarize up on ur write out-

1. pre cat lambda spoilt- get worry

2. post cat lambda spoilt- live wif it.

 

Correct???

 

Btw, can we say if e pre cat lambda is kaput, most of e time e A/F mixture is tune richer by ECU, to safe guard e engine??

 

i wouldn't say "live with it". i would rather say the car will still be functional, but you should get it fixed ASAP to prevent other more serious issues (ie fire).

 

yes, if pre-cat O2 sensor is malfunctioning, the ECU will override with its preset parameters, which is like how your car behaves when you first start it in the morning (high revs, very rich fuel mixture).

[Kyojin]

for cars with one lambda sensor (mine is EU2 compliant only), would it be pre or post-cat ? I presume pre-cat ?

 

that's pre-cat. if there's only 1 O2 sensor, there's nothing for the system to compare, so it can't be a post-cat.