Technical p0141 help please

[markwi]

hi all
my friends panda 1.2 has had this p0141 fault for a a while now.... ever since the exhaust was changed a couple of years ago:chin: but now the new mots are here need to try and sort it out.
anyway changed the pre and post cat sensors twice, car runs fine, emissions apparently are fine. reset the code start car no engine light, stop then restart, light reappears. fuse 11 in engine bay hasnt blown. so if anybody could point me where to go it would be much appreciated.... thank you!

 

[jrkitching]

hi all
my friends panda 1.2 has had this p0141 fault for a a while now.... ever since the exhaust was changed a couple of years ago:chin: but now the new mots are here need to try and sort it out.
anyway changed the pre and post cat sensors twice, car runs fine, emissions apparently are fine. reset the code start car no engine light, stop then restart, light reappears. fuse 11 in engine bay hasnt blown. so if anybody could point me where to go it would be much appreciated.... thank you!

The only way I can imagine a new exhaust would affect this would be a change in backpressure, though I'd have expected most of that to come from the maniverter (which presumably is still original). I'd be interested to know what happens if you stick a bit of rag up the tailpipe after resetting the code (but don't try driving it like this ).

IIRC the pre and post cat sensors are identical; you could also try swapping them round.

 

[markwi]

tried swapping sensors, and yes it is the original maniverter. actually were recently on the second exhaust since this problem started. will try the rag later, i assume your trying to add a little more pressure in the system?!

 

[koalar]

Isn't it the heating element of the O2 behind the CAT

And its been changed twice

I would start by making sure there is power to the heater. There's resistance across the element and a path to earth


Before even that I would remove the connector get a good light looks at the contacts check the wires at the end of the connector and run my fingers along the wire checking for chaffing or melting.

 

[jrkitching]

will try the rag later, i assume your trying to add a little more pressure in the system?!

That was my thinking, yes. I'm not too hopeful of a result, but at least it's something easy to try!


Koalar's suggestion of checking the O2 sensor wiring is sound.

 

[markwi]

Isn't it the heating element of the O2 behind the CAT

And its been changed twice

I would start by making sure there is power to the heater. There's resistance across the element and a path to earth


Before even that I would remove the connector get a good light looks at the contacts check the wires at the end of the connector and run my fingers along the wire checking for chaffing or melting.

so far, yes have resistance across the heater. while engine running and sensor disconnected, have 10.5 volts across the heater circuit. if i measure live heater circuit to battery earth i have 14 volts. when you say a path to earth you mean the heater circuit negative?! i cant seem to get an earth resistance on the grey wire ( cant remember colour on loom side) weather car running or not.

 

[koalar]

so far, yes have resistance across the heater. while engine running and sensor disconnected, have 10.5 volts across the heater circuit. if i measure live heater circuit to battery earth i have 14 volts. when you say a path to earth you mean the heater circuit negative?! i cant seem to get an earth resistance on the grey wire ( cant remember colour on loom side) weather car running or not.

The heater circuit on the sensor should have two wires the same colour.

The resitance between them should be quite low something like 15 ohms(engine off)


On the wiring harness side the corresponding pins to the two wires the same colour on the sensor


Measure the resistance between these to pins. Engine off should be open circuit (engine off)


Set the multimeter to volts. One lead on the battery negative the other on the connector and it should read 0 volts and 14 volts (Engine cold. Engine on)

Move the lead on the battery to the positive terminal and the other lead to the pin that read 0 volts and it should read 14 volts (engine cold. Engine on)


Make sure you know what you are dong as shorting or measuring the wrong thing can cause damage.



Take a look on youtube there should be a tuturial.

 

[markwi]

The heater circuit on the sensor should have two wires the same colour.

The resitance between them should be quite low something like 15 ohms(engine off)


On the wiring harness side the corresponding pins to the two wires the same colour on the sensor


Measure the resistance between these to pins. Engine off should be open circuit (engine off)


Set the multimeter to volts. One lead on the battery negative the other on the connector and it should read 0 volts and 14 volts (Engine cold. Engine on)

Move the lead on the battery to the positive terminal and the other lead to the pin that read 0 volts and it should read 14 volts (engine cold. Engine on)


Make sure you know what you are dong as shorting or measuring the wrong thing can cause damage.



Take a look on youtube there should be a tuturial.

ok, so i have
5 ohms across the heater
corresponding wires on harness side (brown wire and pink with white stripe) are open circuit.
battery negative to brown wire 14 volt and 3.5 to pink wire with white stripe
battery positve to pink/white wire 10.6 volt

 

[koalar]

ok, so i have
5 ohms across the heater
corresponding wires on harness side (brown wire and pink with white stripe) are open circuit.
battery negative to brown wire 14 volt and 3.5 to pink wire with white stripe
battery positve to pink/white wire 10.6 volt

Well done.

Its almost certain that the heater element in the O2 sensor is fine

Looks like its being supplied a voltage

Looks like its got a return to earth and no sort circuit.

Running out of options now.

You have cleared the code as I believe this on doesn't self clear

The only place I can think of is the connector itself

There are several way to check this. If the sensor comes out easy you could just connect back up but leave out and start the engine from cold for a few seconds and see if it warms up. This is the best as it tests everything as it would work in use. Be careful not to burn yourself.

Or

Connect it back up and back probe the connector on the sensor side if there enough room


Or pierce the sensor heater wire with a pin and test the same as you have already done. If you do it this way be very careful not to short the pin to any metal. Plus you will need to seal the hole as water will be sucked in and corrode the wire from the inside.

 

[markwi]

Well done.

Its almost certain that the heater element in the O2 sensor is fine

Looks like its being supplied a voltage

Looks like its got a return to earth and no sort circuit.

Running out of options now.

You have cleared the code as I believe this on doesn't self clear

The only place I can think of is the connector itself

There are several way to check this. If the sensor comes out easy you could just connect back up but leave out and start the engine from cold for a few seconds and see if it warms up. This is the best as it tests everything as it would work in use. Be careful not to burn yourself.

Or

Connect it back up and back probe the connector on the sensor side if there enough room


Or pierce the sensor heater wire with a pin and test the same as you have already done. If you do it this way be very careful not to short the pin to any metal. Plus you will need to seal the hole as water will be sucked in and corrode the wire from the inside.

right had another look this morning.
took sensor out started car, no heat
disconnected sensor and connected its heater wires across battery and it heated up.
reconnected then measured voltage as close as i could get to sensor 14 volt on both white wires to negative. then measured voltage just before the harness wires enter the multi pin connector, same reading, 14 volts to negative.
so would i be right in thinking negative fault? obviously its a switched negative as mentioned previously theres no reading to negative until the cars running

thanks for this by the way !!

 

[koalar]

Sounds like there is high resistance in the earth wire when you tested it was 10.6 volts instead of battery volts. Either in the connectors or the insulation is damaged and touching the chassis or exhaust

 

[markwi]

Sounds like there is high resistance in the earth wire when you tested it was 10.6 volts instead of battery volts. Either in the connectors or the insulation is damaged and touching the chassis or exhaust

sorry for long wait ...... usually i get an email when i get a reply.
do you know where the other end of the pink white wire goes?...... before i try and pull the loom apart. if not i'll have to try and get a wiring diagram.

thank you!

 

[koalar]

As far as I remember its direct to the ECU. But don't quote me on this. First I might have remembered wrong. Second the Haynes manual is very hazy on the engine management and dash wiring diagrams.

 

[markwi]

As far as I remember its direct to the ECU. But don't quote me on this. First I might have remembered wrong. Second the Haynes manual is very hazy on the engine management and dash wiring diagrams.

thank you, will have a look in the next day or so.