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Oxygen Sensor (O2) Bank 1, Sensor 2 DIY
03-26-17, 01:02 AM
#122
11-06-17, 10:35 AM
#123
Driver School Candidate
hi all and sorry for reviving an old thread...
My OBD2 scanner shows no voltage from the B1S2 O2 sensor, 0.00V thus making the Short term fuel trim to 99%. But when i measured the O2 sensor it shows 14ohm which is as per car manual.
is there anything i should check before replacing the 02 sensor or is it confirmed a faulty o2 sensor even though the sensor Ohms reading is within spec?
thanks again for a great thread.
My OBD2 scanner shows no voltage from the B1S2 O2 sensor, 0.00V thus making the Short term fuel trim to 99%. But when i measured the O2 sensor it shows 14ohm which is as per car manual.
is there anything i should check before replacing the 02 sensor or is it confirmed a faulty o2 sensor even though the sensor Ohms reading is within spec?
thanks again for a great thread.
11-06-17, 11:27 AM
#124
Pole Position
Bank 1 Sensor 2 is for measuring catalyst efficiency not for setting fuel trim. Fuel trim is determined by the Bank 1 Sensor 1 and Bank 2 Sensor 1. I've never heard of a fuel trim of 99%. Usually short term trim is limited to 25-40%. Do you have long and short term trim numbers for banks 1 and 2. Also, where did you get the 14 ohm measurement data? That sounds like it might be the internal heater resistance of the sensor. The heater can be good while the sensor is bad but you need to check that power is getting applied to the heater to verify circuit integrity.
11-06-17, 07:52 PM
#126
Pole Position
Looks like there may be two things going on here.
1) Looks to me like you have a vacuum leak somewhere in the induction system based on the B1S1 and B2S1 sensor readings. A vacuum leak will cause too much un-metered air going into the engine so the system will try to adjust by making the mixture richer, thus both short term trims are probably maxed out. Check the flex pipe between the MAF and the throttle body for cracks. Also look for any vacuum lines that may be leaking. Low fuel pressure is another possibility but this would show up as poor acceleration under WOT.
2) The B1S2 problem is odd. Not sure why your scanner would report a fuel trim issue based on that sensor since it is downstream from the catalytic converter. Check your codes for a catalyst efficiency problem. This would get reported if the B1S2 sensor went bad.
1) Looks to me like you have a vacuum leak somewhere in the induction system based on the B1S1 and B2S1 sensor readings. A vacuum leak will cause too much un-metered air going into the engine so the system will try to adjust by making the mixture richer, thus both short term trims are probably maxed out. Check the flex pipe between the MAF and the throttle body for cracks. Also look for any vacuum lines that may be leaking. Low fuel pressure is another possibility but this would show up as poor acceleration under WOT.
2) The B1S2 problem is odd. Not sure why your scanner would report a fuel trim issue based on that sensor since it is downstream from the catalytic converter. Check your codes for a catalyst efficiency problem. This would get reported if the B1S2 sensor went bad.
11-06-17, 08:04 PM
#127
carlmc,
please report your Long term and short term trims at idle and at 2000 RPM. Also report your idle RPM.
MAFs go bad in our cars. And having high trim values on both banks at high RPM can most likely be explained by the MAF, in the absence of a large crack in the hose between the MAF and the throttle body.
please report your Long term and short term trims at idle and at 2000 RPM. Also report your idle RPM.
MAFs go bad in our cars. And having high trim values on both banks at high RPM can most likely be explained by the MAF, in the absence of a large crack in the hose between the MAF and the throttle body.
11-06-17, 08:11 PM
#128
Check out the video in this thread for some good information on how to interpret the trim data
https://www.clublexus.com/forums/rx-...uel-trims.html
Those short term trims should head to 0 as the long term trim adjusts
I think the 99% reading is nonsense which makes me question the B1S2 reported voltage too
Do you have any codes or are you chasing something else?
https://www.clublexus.com/forums/rx-...uel-trims.html
Those short term trims should head to 0 as the long term trim adjusts
I think the 99% reading is nonsense which makes me question the B1S2 reported voltage too
Do you have any codes or are you chasing something else?
11-06-17, 09:57 PM
#129
Driver School Candidate
Ok guys..gonna take the idle and 2000rpm readings again...
Confusingly no codes but my fuel consumpation is verrry bad atm...so far seems like no cracks or passing in the air intake..gonna make a second check again
Confusingly no codes but my fuel consumpation is verrry bad atm...so far seems like no cracks or passing in the air intake..gonna make a second check again
11-06-17, 10:41 PM
#130
Driver School Candidate
Check out the video in this thread for some good information on how to interpret the trim data
https://www.clublexus.com/forums/rx-...uel-trims.html
Those short term trims should head to 0 as the long term trim adjusts
I think the 99% reading is nonsense which makes me question the B1S2 reported voltage too
Do you have any codes or are you chasing something else?
https://www.clublexus.com/forums/rx-...uel-trims.html
Those short term trims should head to 0 as the long term trim adjusts
I think the 99% reading is nonsense which makes me question the B1S2 reported voltage too
Do you have any codes or are you chasing something else?
11-06-17, 10:51 PM
#131
Driver School Candidate
ok guys...
Idle 895rpm
air flow rate from air flow sensor: 6.58g/s
b1s1 voltage: 0.655v
short term fuel trim b1s1: 19.5%
b1s2 voltage: 0.00v
short term fuel trim b1s2: 99.2%
b2s1 voltage:0.660v
short term fuel trim b2s1: 19.5%
at 2000rpm
air flow rate from air flow sensor: 14.9g/s
b1s1 voltage: 0.655v
short term fuel trim b1s1: 19.5%
b1s2 voltage: 0.00v
short term fuel trim b1s2: 99.2%
b2s1 voltage:0.660v
short term fuel trim b2s1:20.3%
at idle
short term fuel trim bank 1 : 19.5%
Long term fuel trim Bank 1 : 30.5%
Short term fuel trim Bank 2 :19.5%
Long term fuel trim Bank 2 : 30.5%
MAF problem? done the maf cleaning procedure before....
Idle 895rpm
air flow rate from air flow sensor: 6.58g/s
b1s1 voltage: 0.655v
short term fuel trim b1s1: 19.5%
b1s2 voltage: 0.00v
short term fuel trim b1s2: 99.2%
b2s1 voltage:0.660v
short term fuel trim b2s1: 19.5%
at 2000rpm
air flow rate from air flow sensor: 14.9g/s
b1s1 voltage: 0.655v
short term fuel trim b1s1: 19.5%
b1s2 voltage: 0.00v
short term fuel trim b1s2: 99.2%
b2s1 voltage:0.660v
short term fuel trim b2s1:20.3%
at idle
short term fuel trim bank 1 : 19.5%
Long term fuel trim Bank 1 : 30.5%
Short term fuel trim Bank 2 :19.5%
Long term fuel trim Bank 2 : 30.5%
MAF problem? done the maf cleaning procedure before....
11-07-17, 05:19 AM
#132
Pole Position
Idle is high, should be around 700-750 rpm when engine is fully warmed up and all accessories are turned off.
MAF is way high, about double what it should be. Normal is around 3.1 to 3.3 g/S at normal idle.
Do your fuel trim numbers improve at cruise rpm (2000-2500rpm). If they trend toward normal numbers at higher rpm this is a good indication of a vacuum leak.
Also curious what the trim numbers would be if you simply unplugged the MAF and let the ECU use default limp-mode numbers.
MAF is way high, about double what it should be. Normal is around 3.1 to 3.3 g/S at normal idle.
Do your fuel trim numbers improve at cruise rpm (2000-2500rpm). If they trend toward normal numbers at higher rpm this is a good indication of a vacuum leak.
Also curious what the trim numbers would be if you simply unplugged the MAF and let the ECU use default limp-mode numbers.
11-07-17, 07:32 AM
#133
Driver School Candidate
Idle is high, should be around 700-750 rpm when engine is fully warmed up and all accessories are turned off.
MAF is way high, about double what it should be. Normal is around 3.1 to 3.3 g/S at normal idle.
Do your fuel trim numbers improve at cruise rpm (2000-2500rpm). If they trend toward normal numbers at higher rpm this is a good indication of a vacuum leak.
Also curious what the trim numbers would be if you simply unplugged the MAF and let the ECU use default limp-mode numbers.
MAF is way high, about double what it should be. Normal is around 3.1 to 3.3 g/S at normal idle.
Do your fuel trim numbers improve at cruise rpm (2000-2500rpm). If they trend toward normal numbers at higher rpm this is a good indication of a vacuum leak.
Also curious what the trim numbers would be if you simply unplugged the MAF and let the ECU use default limp-mode numbers.
tried disconnecting the battery today and reset the ecu...all fuel trim went to 0% for short and long term fuel BUT after a few minutes in idle went back to above reading...
11-07-17, 07:52 AM
#134
I would replace the MAF. I had lesser values but high LT trims at both idle and 2000 RPM for both banks. The CEL was P0171 (bank1 lean), but both banks were close in LT trim, around 20%. Cleaning the mAF did nothing. Replacing the MAF fixed the high RPM trims, but I still had some elevated LT trims at idle, around 10-15% with them higher on bank2. I found a couple of vacuum leaks on bank 2 and improved the trims at idle.
FWIW, I bought a Denso MAF 197-6020 at Advance Auto.
FWIW, I bought a Denso MAF 197-6020 at Advance Auto.
Last edited by Lexmus; 11-07-17 at 07:54 AM. Reason: added data
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carlmc (11-07-17)
11-07-17, 07:54 AM
#135
Driver School Candidate
I would replace the MAF. I had lesser values but high LT trims at both idle and 2000 RPM for both banks. Cleaning the mAF did nothing. Replacing the MAF fixed the high RPM trims, but I still had some elevated LT trims at idle, with them higher on bank2. I found a couple of vacuum leaks on bank 2 and improved the trims at idle.
FWIW, I bought a Denso MAF 197-6020 at Advance Auto.
FWIW, I bought a Denso MAF 197-6020 at Advance Auto.