Greetings all. My 96 Pathy has been throwing a few codes for a few years, but it really never concerned me until I recently moved into an area that requires emissions testing via a scanner / analyzer. As a few codes are emissions related, I'm hoping to avoid the large expense of paying to replace a bunch of parts unnecessarily - ANY help at all will be appreciated!
The codes I am throwing are:
P0156 - Rear Heated O2 sensor, left bank
P0172 - Fuel injection system (bank 1) too rich
(perhaps unrelated, this one as well) P0325 - Knock sensor circuit, left bank.
So, I've been trying to interpret these codes and replace the source of the problem; Nissanhelp sez the O2 code is coming from the post-cat sensor, perhaps replace that, ya? However, the rich condition code lists the possible problem being the PRE-cat sensor (among other possible causes...) - so I'm not sure where the source of the problem is.
Can anyone shed some light on this and possibly give a clue as to where the problem may be, so I can hopefully avoid the scenario of replacing things willy-nilly??
Thanks very munch, --ponga
96 Pathy OBD-II codes / emissions Help please
Re: 96 Pathy OBD-II codes / emissions Help please
O2 and and richness can be related by a lazy O2 sensor and if heated as you are saying the power source for the heated element could be compormised.
Test for voltage at the heated part.
Test the leads
See if you can spray cleaner over the sensor
If the sensor is 60,000 miles old, replace
Reset the MIL light and drive as usual. The code may or may not come back. If it returns you may be rich, check your intake manifold for back soot, check your exhaust tail pipe for black soot.
A lazy O2 sensor is the cause of rich mixture since the hi lo cycle cannot keep up and the leaning of the mixture can not be maintained and thus a rich mixture is the predominant mixture and the O2 sensor chases its signals ans the signals cannot keep pace with the cycles and it all falls apart.
So try the cleaning and see if it works before replacing things but the total mileage on the vehicle will dictate...sensors do wear, do get lazy and a change out is needed
Test for voltage at the heated part.
Test the leads
See if you can spray cleaner over the sensor
If the sensor is 60,000 miles old, replace
Reset the MIL light and drive as usual. The code may or may not come back. If it returns you may be rich, check your intake manifold for back soot, check your exhaust tail pipe for black soot.
A lazy O2 sensor is the cause of rich mixture since the hi lo cycle cannot keep up and the leaning of the mixture can not be maintained and thus a rich mixture is the predominant mixture and the O2 sensor chases its signals ans the signals cannot keep pace with the cycles and it all falls apart.
So try the cleaning and see if it works before replacing things but the total mileage on the vehicle will dictate...sensors do wear, do get lazy and a change out is needed
Re: 96 Pathy OBD-II codes / emissions Help please
ARKQX33V6 - Understood ; but when you suggest to check / replace the O2 sensor, are you referring to the post-cat sensor, the pre-cat sensor, or both?? ()
REALLY appreciate the reply - I don't believe I am actually running rich because it does not smell that way, no sooty tail pipes, and despite the fact that it's a 96, I'm getting dead-on the EPA estimated MPG that was set way back when. Thanks again, kinda worried that these emissions monkeys will plug in an summarily fail my poor Pathy
REALLY appreciate the reply - I don't believe I am actually running rich because it does not smell that way, no sooty tail pipes, and despite the fact that it's a 96, I'm getting dead-on the EPA estimated MPG that was set way back when. Thanks again, kinda worried that these emissions monkeys will plug in an summarily fail my poor Pathy
Re: 96 Pathy OBD-II codes / emissions Help please
Your MIL will indicate left, right, pre or post depending on the quantity of O2 sensors. With an indication of a trouble code for a particular sensor the ECU which is by no means the brains of the system but more an indicator. As an indicator that ECU at that time indicated a possible problem. At that time it is not a trend, you must have at least 3x an indication with the same fault to indicate that a trend is happening.
Record all MIL faults and with time verification can be done. Sensors are a one time at a time indicators that have a threshold to hand out their indication. It is this threshold that is variable even if the threshold design is fixed. Why? These devices are massed produced and have a tolerance that varies just a little from one to the other. Two of the same sensors may be exact but very rare, they are close, very close and that closeness is the tolerance factor and this changes when that sensor is to be triggered but the ECU is built around these tolerances.
Even ECUs are not exact, close but not the same and it's this about the same that gives out a variable but close output.
When you have the output about the same at many times you may have a trend and it's the trend you need to work on.
So if you have the same trouble code reset and reappear three times then you may have a problem. If it is a heated O2 sensor the heat circuit or the actual O2 circuit may be at fault. Some sensors are not heated and they last longer but do become retarded in their action and thus create problems for a fast acting reacting ECU.
The engine always reacts to the ECU, the ECU reacts to the sensors, SENSORS react to their conditions, all this action and reaction takes time. Some reactions are handled with memory and only after a 2nd or 3rd reaction does the MIL come on.
You have a 1996 vehicle, that is the first year for the OBDII and there may be some gliches. The 96, 97, and 98 have far less real parameter used as compared to newer years. This may be a blessing more than a curse.
Repairing sensors is more work than replacing them, but they both require unplugging, letting the harness free, removing the sensor from its rusted bed. Then a trial and error of sprays to clean them then replacing that old sensor, hooking it back up and resetting the MIL and patience as you drive to see if it returns.
Time spent under a car is a PITA. Better to stay away from the bottom of the car, reset the MIL at leaSt 3 x to see if it's a trend then after the 3rd time buy a new sensor than go car diving once and fix the problem.
Or forget about it, tape up the MIL and reap the benefits of poor gas mileage, a rich engine and wait for a decoking process that will hinder cooling, render the knock sensors into play and destroy the catalyst and end up with at least $1500 in repair costs as compared to $150.
Although it always cost you, better the devil you know than the devil awaiting.
Record all MIL faults and with time verification can be done. Sensors are a one time at a time indicators that have a threshold to hand out their indication. It is this threshold that is variable even if the threshold design is fixed. Why? These devices are massed produced and have a tolerance that varies just a little from one to the other. Two of the same sensors may be exact but very rare, they are close, very close and that closeness is the tolerance factor and this changes when that sensor is to be triggered but the ECU is built around these tolerances.
Even ECUs are not exact, close but not the same and it's this about the same that gives out a variable but close output.
When you have the output about the same at many times you may have a trend and it's the trend you need to work on.
So if you have the same trouble code reset and reappear three times then you may have a problem. If it is a heated O2 sensor the heat circuit or the actual O2 circuit may be at fault. Some sensors are not heated and they last longer but do become retarded in their action and thus create problems for a fast acting reacting ECU.
The engine always reacts to the ECU, the ECU reacts to the sensors, SENSORS react to their conditions, all this action and reaction takes time. Some reactions are handled with memory and only after a 2nd or 3rd reaction does the MIL come on.
You have a 1996 vehicle, that is the first year for the OBDII and there may be some gliches. The 96, 97, and 98 have far less real parameter used as compared to newer years. This may be a blessing more than a curse.
Repairing sensors is more work than replacing them, but they both require unplugging, letting the harness free, removing the sensor from its rusted bed. Then a trial and error of sprays to clean them then replacing that old sensor, hooking it back up and resetting the MIL and patience as you drive to see if it returns.
Time spent under a car is a PITA. Better to stay away from the bottom of the car, reset the MIL at leaSt 3 x to see if it's a trend then after the 3rd time buy a new sensor than go car diving once and fix the problem.
Or forget about it, tape up the MIL and reap the benefits of poor gas mileage, a rich engine and wait for a decoking process that will hinder cooling, render the knock sensors into play and destroy the catalyst and end up with at least $1500 in repair costs as compared to $150.
Although it always cost you, better the devil you know than the devil awaiting.