Oxygen Sensor question
- Thread starter 04SR54me
- Start date
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the answer is yes! Do pay attention to the quality and TYPE of O2 sensors that're going back into the engine. Amazon has lots of knock off Denso products. Also, pre-cat vs post-cat sensors may have different part numbers. Pre-cat sensors are often known as "air fuel ratio" sensors.
O2 sensor update/frustration
Had the two upstream sensors replaced with correct Denso from Rock Auto. The engine light is gone, but the VSC and Trac Off persist. When i start the car up its off, but as soon as i drive it, it goes on and stays on. I used the scanner and it shows no error codes. Gas cap good, MAF sensor cleaned. No vacuum leaks. Car seems to run fine.
So, what do I do?
Thanks.
Had the two upstream sensors replaced with correct Denso from Rock Auto. The engine light is gone, but the VSC and Trac Off persist. When i start the car up its off, but as soon as i drive it, it goes on and stays on. I used the scanner and it shows no error codes. Gas cap good, MAF sensor cleaned. No vacuum leaks. Car seems to run fine.
So, what do I do?
Thanks.
MikeinNH67
Senior Member
If it's just those 2 lights, I would try the zero point calibration you can do. Check it out in the stickies section. Older code readers can mess it up which will make the lights go on.
oxy sensor question
My mechanic put the o2 sensors in because one i got under the car and saw the limited access, I paid the $$ to have it done.
The VSC and Track Off lights came on once i start driving, not at idle when first starting car. But, later that day, the engine light came back on.
I did that reset thing a few years ago when this happened, but i did not have the engine light on,
My mechanic is supposed to use a more sophisticated scanner tomorrow. I guess i'll see. I did not have any codes show when i got home and used my cheap scan tool. But then the engine warning light returned. Pretty confusing.
My mechanic put the o2 sensors in because one i got under the car and saw the limited access, I paid the $$ to have it done.
The VSC and Track Off lights came on once i start driving, not at idle when first starting car. But, later that day, the engine light came back on.
I did that reset thing a few years ago when this happened, but i did not have the engine light on,
My mechanic is supposed to use a more sophisticated scanner tomorrow. I guess i'll see. I did not have any codes show when i got home and used my cheap scan tool. But then the engine warning light returned. Pretty confusing.
Update: So, after the two upstream O2 sensors were replaced, I was still getting the error codes. I did the zero point callibration with no change. Then I did a complete battery disconnect, let it sit for 10 minutes with the headlights on to drain the circuits and reconnected. Everything gone! I was excited until after 200 miles, the check engine, VSC and Track off lights returned. 
I pulled out my cheap scanner and I got the P0174: system too lean for bank 2, P0171: system too lean bank 1 and another P0174 system too lean Bank 2. I don't know what to do. Vacuum leak test passed according to scanner. The new O2 sensors are Denso.
As an aside, anyone recommend a user friendly, resonably priced scanner that would help diagnose the problem? Thx.
I pulled out my cheap scanner and I got the P0174: system too lean for bank 2, P0171: system too lean bank 1 and another P0174 system too lean Bank 2. I don't know what to do. Vacuum leak test passed according to scanner. The new O2 sensors are Denso.
As an aside, anyone recommend a user friendly, resonably priced scanner that would help diagnose the problem? Thx.
Update: So, after the two upstream O2 sensors were replaced, I was still getting the error codes. I did the zero point callibration with no change. Then I did a complete battery disconnect, let it sit for 10 minutes with the headlights on to drain the circuits and reconnected. Everything gone! I was excited until after 200 miles, the check engine, VSC and Track off lights returned.
I pulled out my cheap scanner and I got the P0174: system too lean for bank 2, P0171: system too lean bank 1 and another P0174 system too lean Bank 2. I don't know what to do. Vacuum leak test passed according to scanner. The new O2 sensors are Denso.
As an aside, anyone recommend a user friendly, resonably priced scanner that would help diagnose the problem? Thx.
How did you determine the gas cap is still good?
Unless it's new and OEM I would replace it with a new OEM cap, aftermarket caps are hit and miss with sealing properly, also make sure the metal gas filler neck sealing surface is sooth and clean.
I had the same lights come on and replaced my old cap with a new OEM cap and the lights went off on their own within 30 or so miles on my drive home.
You need to check with another dealer, that dealer is trying to rip you off!!
I paid less than $25 for mine, full retail is about $32.
Toyota Gas Cap - Guaranteed Genuine from ToyotaPartsDeal.com)
MikeinNH67
Senior Member
This is probably beyond this forum at this point, I think you need a good troubleshooter that has the right tools. May need to do a smoke test to look for leaks and such. Monitor fuel trims etc.
Curious, did you clear the codes or just hope they would go away? These cars seem to need a couple drive cycles with varying speeds for codes to clear themselves.
Curious, did you clear the codes or just hope they would go away? These cars seem to need a couple drive cycles with varying speeds for codes to clear themselves.
Last edited:
earthrealm
Senior Member
saw your post late,
you may just likely have a leak in the exhaust system. a spacer would have been a better and cheaper option, as a new sensor will still throw the codes.
i use a phone app with a bluetooth scanner. it has abs,srs and engine code read capability, so i actually dont need an expensive hand held scanner
check it out.Amazon.com
and MOTORDATA obd phone app