Technical Lambda Sensor replacement

[jonyid]

Hi there,

i have had a read around and am sure i can change the pre-cat lambda sensor without issue but the post-cat one, will i need to jack the car up on the o/s or can it be done on the floor?

EDIT: the error codes that appear are:

P0141-O2 SENSOR (12) O2 Sensor Heater Cct Malfunction (Bank 1 Sensor 2)
P0135-O2 SENSOR (6) O2 Sensor Heater Cct Malfunction (Bank 1 Sensor 1)

they have been there a long time but the car has never failed an MOT nor is the MPG being affected?

 

[Ziggy122]

Both sensors are saying that the heating element inside the lambda is taking too long to allow it to swap to closed loop

But this time is based on the engine coolant temperature to determine how long that really is

So it could point to that there is possible
2x Failed Sensors (lambda) or the coolant sensor is telling porkies and confusing the car

Ziggy

 

[fingers99]

My guess is that it's a wiring issue rather than the lambdas themselves. Cct = circuit. Check out the wiring.

 

[atom0007]

You can do it on the floor

 

[jonyid]

Thanks for your replies guys, with regards to the wiring, I'll check the connection each sensor clips into but is there any other part I should be checking?

 

[Ziggy122]

Thanks for your replies guys, with regards to the wiring, I'll check the connection each sensor clips into but is there any other part I should be checking?

i'd be checking the resistance of the sensors with a Multimeter on the element pins
If it comes back as infinity (1 .00) then its probably dead
But i'd do a resistance check from pin to ecu connector to be sure

Ziggy

 

[jonyid]

Cheers mate I'll try and get a multimeter from somewhere, and just to clarify the element pins being where it clips to the ecu or is it elsewhere?

 

[Ziggy122]

Cheers mate I'll try and get a multimeter from somewhere, and just to clarify the element pins being where it clips to the ecu or is it elsewhere?

Yea - its what i would do personally to start with

From the Multi pin connector to the Big multi plug on the back of the ECU

(best disconnecting both from ecu)

Prob from the wire to the ecu and see what you get
If its open circuit (infinity reading) on the meter, then thats why the sensors aint happY

Wiring Diagram in haynes mayforwell help you understand whats what


Ziggy

 

[jonyid]

I'll have to have a look at the Haynes and seek advice from good ol' dad who may be able to help as I'm a novice with electrics but would be able to change them no bother. If money isn't an issue, would it be easier to just replace both?

 

[fingers99]

Not if the fault is outside the lambda!

Fault codes tend to narrow it down a bit, rather than give definitive answers.

 

[Ziggy122]

hence why I suggest you do a quick resistance check on both sensors to ensure that the elements haven't gone open circuit, but as im with fingers here, its abit odd that BOTH sensors are reporting the same fault all of a sudden.....

If a fuse had blown affecting them - the speedo sensor is powered off the same line so the speedo wouldn't work either

Ziggy

 

[jonyid]

Thanks guys, I guess its not the fuse then. Hoping to borrow a mates multimeter tonight can check the resistance then. I have googled ways to check and it suggest running the engine so that they're warm. Placing the red on the red wire coming from the sensor to the clip and then the black to a grounding part on the car, leaving the sensor screwed in and clipped into the ECU connector. is this right?

 

[jonyid]

Yea - its what i would do personally to start with

From the Multi pin connector to the Big multi plug on the back of the ECUdisconnect them both from clips and go from live pin (which out of the 4 is live) to multimeter and black multimeter wire to earth?

(best disconnecting both from ecu) both lambda sensors?

Prob from the wire to the ecu and see what you get
If its open circuit (infinity reading) on the meter, then thats why the sensors aint happYso the non-sensor clip pick the live one again and check to make sure that wiring from ECU is okay?

Wiring Diagram in haynes mayforwell help you understand whats what


Ziggy

shall i also disconnect the battery or is that not necessary?

 

[jonyid]

Got hold of the multimeter but wanted to bump this to make sure all was covered and I didn't mess anything up?

 

[atom0007]

Here's the order I'd go in.

Disconnect one sensor, probe the heater pins on the sensor itself. As ziggy says, if open circuit (infinite resistance), heater is dead. You can take it off the car if you want, or leave it in.

If dead heater, repeat for other sensor. Heater dead too? Replace both.

If the first sensor heater is ok on the other hand, then as already said, is likely to be a problem with the wiring backwards. This is the more likely scenario, I wouldn't expect both lambda sensors to die at once.

Then it's just a case of measuring the resistance over the wire from the sensor back to the ecu.

If that's ok, then is would assume its a problem with the ecu, and that's out of my depth....

 

[jonyid]

okay great cheers mate, i know i'm annoying people but which one is the heater pin?

 

[Ziggy122]

okay great cheers mate, i know i'm annoying people but which one is the heater pin?

This MAY help
I think in this one he's explains which wire is which




Ziggy

 

[atom0007]

I can check tomorrow, I'd guess it's the two wires that look identical.

 

[jonyid]

and i then check both wires with the multimeter?

 

[jonyid]

I can check tomorrow, I'd guess it's the two wires that look identical.

So i've jsut checked the two heater pins (wire for future reference) and cant get a reading from them....lambda sensor it is.