Nissan primera P12

[andybaz]

Hi all, i will admit, oxy sensors/lambda sensors always confuse me,as these report what they see and are not always the fault which i understand, the heating side no probs, as yes it simply heats the sensor to operating temperature quicker to improve fuel econmy etc is what i am lead to believe.

So , i have been round to look at a nissan primera P12, with obd code P0171 fuel system too lean bank 1 .

Now my understanding is, this 1st sensor measures whats coming out of the engine, the second sensor after the cat measures the cat emmission and both items report back to the ecu which then controls fueling, along with other data from other sensors.

I have watched the MAF sensor, on live data as a voltage value, and this increase with throttle response, coolant temp is correctly reading, but in live data for both oxy sensors, should i be seeing more of a switching operation ?, when i take live data, i record at x4.
Also, in the second graph, the MAF i can not show as 'g's, the only option i have is voltage, and if i look down to 'accel voltage' , the 2 raised sections are where i am applying throttle operation, should i be seeing a fluctuating MAS flow voltage ?

Cheers for your time folks, andy

[markt]

going off the graph for the before cat sensor it looks to be only peaking at 0.1 volt ?.way too low and would suspect a faulty sensor off its reading or bad wiring. if an air leak would cause this reading then i would expect to see high revs or possible idle fault also.
the after cat sensor is possibly reading high due to the ecu trying to richen the fuel as its seeing the lean mixture from the front sensor. a good enough display for the front sensor but would just confoirm its switching ratio on me scope or multimeter.
just a little info for you there Andy

[andybaz]

I can use a multimeter , so that would be back probing the multiplug on the feed and return and seeing the voltage rise/drop/rise/drop etc, the motor is low mileage, no apparent visual or audible symptons as advised on the s'pro via t'shooter, wish all cars were this clean under the bonnet to work on .
So no voltage change, then im on the right track, will update as i go.

Back in my comfort zone tomorrow - toyota's , on a dirty caked solid with muck hilux gearbox removal for strip investigation, im sure the mushrooms growing under it will keep me sane

[markt]

yep..just earth lead to battery then pos lead to sensor output.

[andybaz]

Spot on Mark !!

Due to lack of transport, a colleague put this on for me, car runs sweet, but will be going back to clear codes from his ecu and also get some after fitting ( live data) aswell.

Much appreiated

[markt]

if you get to plug the snappy in have a look to see if there is an adaption re-set you can perform as these can sometimes take a while to fully function off the new sensor.
well done matey

[andybaz]

if you get to plug the snappy in have a look to see if there is an adaption re-set you can perform as these can sometimes take a while to fully function off the new sensor.
well done matey

I would say i was 65% going that way, but its nice to confere with others with wider knowledge and not giving answers but giving little pointers to work with, if you get my drift, also thank you for your time viewing my graphs .

If im ever your way racing my 5th scale motors, i'll come an say hi

[andybaz]

Here we go folks the , data after repacing the FRONT 02 sensor, see a difference straight away and so did the owner