2001 gt o2 sensors and fuel trim

Black GT

Active Member
Sep 8, 2018
148
9
28
Jacksonville, Florida
Hooked my scan tool up to my 2001 gt today to live data to check the o2 sensors. Bank 1 sensor 1 volts went from 0.120 to 0.745 which I think is normal. bank 1 sensor 2 read 0.000 at all rpm's with short term fuel trim read 99.2 %. Bank 2 sensor 1 had a volt range of 0.120 to 0.700 with a stft reading of 8.6 to 19%. Bank 2 sensor 2 volt range was 0.04 to 0.2 with stft of 99.2% .Am I correct thinking that both side down stream sensors are bad? My car does not have a stock exhaust. There are no catalytic converters. It has a straight pipe coming off the exhaust manifolds going into a H pipe. All 4 o2 sensors are in the short part of the H pipe where the pipes meet. From there it goes into flow master mufflers. This was all done by the previous owner. Wondering if this set up could be the problem with the downstream sensors. My car throws code p0174 which is to lean bank 2 and code p0153, o2 sensor bank 2 sensor 1 slow response.
 
  • Sponsors (?)


Am I correct thinking that both side down stream sensors are bad?
IMO it "could" mean they are bad. It could also mean:
  • There's isn't enough heat in the O2 sensors to allow them to work.
  • The O2 heaters are bad
  • There's a wiring fault to/from the O2 sensors.
  • Of course a bad sensor itself.
  • bad PCM
Wondering if this set up could be the problem with the downstream sensors. My car throws code p0174 which is to lean bank 2 and code p0153, o2 sensor bank 2 sensor 1 slow response.
But I have to ask, why are you so concerned about the rear (after cat) O2 sensors? For a 2004 or older model year car the rear O2's won't affect driveability. The DTC codes you are getting are strictly related to the front O2 sensors.

Seems like a better use of time to rule in/out:
  • Intake vacuum leak
  • Exhaust leak before the front O2 sensors.
  • O2 sensors being located too far away from the Motor (not enough heat in the exhaust).
 
  • Like
Reactions: 1 user
I learned something today. Did not know the downstream sensors would not effect the way the car runs. Will not let them bother me anymore then. If it was a intake vacuum leak wouldn't it throw codes on bank 1 and bank 2? The code has appeared 4 different times. I will erase the codes and within 100 miles they reappear. Code is always p0174 which is a lean code for bank 2. No codes for bank 1. The car seems to run the same with or without the codes appearing.
 
If it was a intake vacuum leak wouldn't it throw codes on bank 1 and bank 2?
Not necessarily. What if:
  • the leak is an exhaust leak. Very easy to see how this could affect only one bank.
  • The leak is on one side of the intake. Say for example injector O rings on one side. Or an intake gasket leak on one side.
  • Leak on one side valve cover gasket.
  • Clogged fuel injector.
 
Last edited:
  • Like
Reactions: 1 user