Service engine soon light

[Tony1955]

My service engine light just came on and these are the codes it's showing: P1491- "Vac Bypass Circuit Malfunction"

P0138- HO2S (bank 1 sensor2) Circuit High Input ( rich shift)

P0456- Evaporation Emmision System Leak Detected-(very small leak)

 

Does anyone know what any of this means?

2002 Pathfinder LE 4x4 167000 miles

 

Thanks in advance, Tony

 

P.S. truck getting 14mpg city. Would any of these codes be related to MPG?

Edited April 26, 2014 by Tony1955

[SpecialWarr]

I'm not a real mechanic but the p0138 sounds like a bad oxygen sensor. Easy to change just make sure you get a nissan oem for its correct voltage range. The p0456 evap can is most likly a small hole in the tubing. Also an easy fix. The p1491 is beyond my experience....anyone else have ideas??

 

sent from under Ernest the Pathfinder

 

 

[Tony1955]

I'm not a real mechanic but the p0138 sounds like a bad oxygen sensor. Easy to change just make sure you get a nissan oem for its correct voltage range. The p0456 evap can is most likly a small hole in the tubing. Also an easy fix. The p1491 is beyond my experience....anyone else have ideas??

 

sent from under Ernest the Pathfinder

 

Thanks, Warr...

[ahardb0dy]

Have you downloaded the Factory Service Manual yet? Should be procedures to troubleshoot all the codes.

[Tony1955]

Have you downloaded the Factory Service Manual yet? Should be procedures to troubleshoot all the codes.

 

Not yet, but will do, thanks.

[5523Pathfinder]

My service engine light just came on and these are the codes it's showing: P1491- "Vac Bypass Circuit Malfunction"

P0138- HO2S (bank 1 sensor2) Circuit High Input ( rich shift)

P0456- Evaporation Emmision System Leak Detected-(very small leak)

 

Does anyone know what any of this means?

2002 Pathfinder LE 4x4 167000 miles

 

Thanks in advance, Tony

 

P.S. truck getting 14mpg city. Would any of these codes be related to MPG?

P1491 is a common code on the R50's. It's related to the emissions system, in the left rear if your truck. It's been covered many times around here. Either is clogged, or something is leaking. You I gotta go underneath and look for a 4 ported white valve. Inspect the lines going to it for leaks. You may need to pull it down and check for a clog. There is also a solenoid valve near it that could be sticking or leaking as well. Some R50's have problems with the charcoal canister coming apart and the charcoal beads will clog the lines and stop the system from working correctly.

 

P0138- is for the left rear oxygen sensor, it's probably failed, and again, it's kinda common. There may be a TSB on it, but I can't look at the moment. Yes, it's possible it would affect fuel mileage.

 

P0456- May be related to he first code. Again, gotta get underestimate there and look for leaks. You may need to take it to a shop and have the system smoke checked.

[byob]

As far as the B1S2 02 sensor. There is a TSB for a ecm update and it also recomends replacing both. On the P1491 it is the fuel vapor recovery valve in the back near the gas tank. It looks like a flying saucer it will also cause a small evap leak code. There is no way for the ecm to detect it-it assumes it is bad but look at the lines going to it for cracks and be careful not to top off when filling. I have found fuel in the lines

[Tony1955]

P1491 is a common code on the R50's. It's related to the emissions system, in the left rear if your truck. It's been covered many times around here. Either is clogged, or something is leaking. You I gotta go underneath and look for a 4 ported white valve. Inspect the lines going to it for leaks. You may need to pull it down and check for a clog. There is also a solenoid valve near it that could be sticking or leaking as well. Some R50's have problems with the charcoal canister coming apart and the charcoal beads will clog the lines and stop the system from working correctly.

 

P0138- is for the left rear oxygen sensor, it's probably failed, and again, it's kinda common. There may be a TSB on it, but I can't look at the moment. Yes, it's possible it would affect fuel mileage.

 

P0456- May be related to he first code. Again, gotta get underestimate there and look for leaks. You may need to take it to a shop and have the system smoke checked.

 

Thank you for your help.

[Tony1955]

P1491 is a common code on the R50's. It's related to the emissions system, in the left rear if your truck. It's been covered many times around here. Either is clogged, or something is leaking. You I gotta go underneath and look for a 4 ported white valve. Inspect the lines going to it for leaks. You may need to pull it down and check for a clog. There is also a solenoid valve near it that could be sticking or leaking as well. Some R50's have problems with the charcoal canister coming apart and the charcoal beads will clog the lines and stop the system from working correctly.

 

P0138- is for the left rear oxygen sensor, it's probably failed, and again, it's kinda common. There may be a TSB on it, but I can't look at the moment. Yes, it's possible it would affect fuel mileage.

 

P0456- May be related to he first code. Again, gotta get underestimate there and look for leaks. You may need to take it to a shop and have the system smoke checked.

 

Thank you

[Tony1955]

As far as the B1S2 02 sensor. There is a TSB for a ecm update and it also recomends replacing both. On the P1491 it is the fuel vapor recovery valve in the back near the gas tank. It looks like a flying saucer it will also cause a small evap leak code. There is no way for the ecm to detect it-it assumes it is bad but look at the lines going to it for cracks and be careful not to top off when filling. I have found fuel in the lines

 

Thanks for your help.

[Tony1955]

Thanks for all the input. I'll be getting underneath the truck soon to replace both lower trailing arms ( already did the uppers), and will inspect and replace these parts.