P0141 on Vectra 2.2 direct petrol 2004

[chips]

Hi, i am having an intermittant p0141 fault. The story so far ..... Originally had a post cat lambda sensor with an open circuit heating element, so it was replaced & the fault codes reset. Then what happened was every 100 or 200 miles (1 or 2 days worth) the emisions light would come on again with a P0141. So checked the heater & signal wires from sensor connector to ecu connector - all ok. The heater on the sensor was ok. Managed to change the sensor with another new part (same type). Still get the same fault intermittantly. So i conclude that it is not the sensor or the wiring to the ecu. Now i have seen several posts about P0141, some indicating a wiring open / short, but another said the fault would appear if the sensor did not start to give a correct signal when it was warm as measurd from the coolant sensor. So i checked the coolant sensor and it seems to be reporting a genuine temperature, without wiring probs. Could it be a hole upstream of the post cat sensor allowing oxygen in to make the post cat sensor give bad signals ? If so, how do i detect the leak ? Any suggestions ???

[mattv6diesel]

a leak in the exhaust you would hear. have you had the emissions tested just to see if out at all as the cat might be failing. is it definatly the 2nd sensor

[clive3373]

Have you had your exhaust gasses checked, to see what your levels are.

Did you replace sensor with a exact same genuine bosch one, not a universal one

You might have to replace both sensors.

[chips]

Hi, thanks for your replies, no i haven't had the exhaust tested. Will organise that soon to see what the levels are. However, 6 months ago the emissions test showed :
At fast idle:
CO = 0.00 %vol
HC = 0 ppm
Lambda = 1.03
At Natural Idle:
CO 0.00 %vol
When this test was done, the post cat sensor heating element was open circuit, which was the start of the issue. Subsequently this sensor was replaced with a NTK OZA531-GM22, which is specifically made for my car, as the connector, length of cable, position of cable fixings on the cable were all just so for my car. When i then had the intermittant P0141, i fitted another new NTK sensor, but have the same issue.
Can you get just the emmissions test done, or do you need to put it through an entire mot ?

[chips]

Thnx for all your help so far, and sorry it has taken me an age to get some action! However, i have now the results from 2 emissions tests done recently :

Test 1:
CO % = 0.00 (natural idle = 0.00)
HC ppm = 5
Lambda = 1.03

Test 2:
CO % = 0.00 ( natural idle = 0.1)
HC ppm = 10
Lambda = 1.02

So, both the before and after service tests are good for the MOT. Would i be right in thinking that the cat is working fine, and the air / fuel mix is ok?

Now i rechecked the wiring between the sensor plug & the ecu plug all seems ok. Should i be getting a voltage across the heater elements for the post cat sensor at all times whilst the engine is running, even when it is fully warmed up ? What about when the ignition is just turned on, but without starting the engine ?

Also, the spark plugs which came out from the service were normal colour, if that helps.

[chips]

Have just double checked the voltage on the post cat sensor heating element, & there is 0V at all times (the engine was warm, had been standing for an hour from normal working temp). So this could be the fault ? I have checked all the engine compartment fusebx fuses & all are ok. So is the heater driven directly from the ecu (no fuses, relays etc)? If it is, then my ecu is the problem ? What about taking the ecu apart ? Dangerous ? (used to electronics, soldering etc). Might just be a soldering problem on the ecu?