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Thread: Weird O2 sensor readings
06-09-2013, 12:47 PM #1
Weird O2 sensor readings
Recently I bought an OBDII Bluetooth adapter to monitor my Tahoe's engine performance and see extra/more exact info from the ECU. Currently my o2 sensors are giving conflicting readings.
What do I mean? Well the pre cat sensors at idle were reading a F/T of -1.6% for both the 1x1 and 2x1 sensors. While the post cat sensors are reading a F/T of 99.1% for both 1x2 and 2x2 sensors. Based on the info I've learned these readings are impossible. Does any one have an idea whats up with these readings? I have been getting a p0340 cat three way inefficiency code for the pass side cat recently, but the code keeps going away even tho its a major code that should stay in the ECU for a long time.
Pic from torque app at idle:
1996 Chevy Tahoe LT 5.7L V8 4X4 202,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.
Check out my other mods in My Garage: http://www.gmtruckclub.com/forum/sho...t-Tahoe-4-Door
06-09-2013, 07:36 PM #2
the P0430 code indicates that you have an air leak on the passenger side, or the cat is bad, or that passenger side rear O2 sensor is not connected to the wiring harness, or the wiring is bent, broken, melted, burned, etc...
what is the F/T reading supposed to be of?? it's not fuel trims, because the fuel trims don't go that high...06MonteSS
06-09-2013, 09:26 PM #3
Is it possible that the reading from the rear sensors isn't actually fuel trim like the fronts and it wrong because they don't measure fuel they measure % of co2, co and o2.
Also my p0430 code goes away on its own sometimes and only sporadically shows up. It makes trying to figure out what I need to fix very hard. Also the pass side used to have a weird sound for a while, which is now gone) I have a video of it I'll post and the pass side rear sensor is brand new (AC Delco)
06-09-2013, 09:31 PM #4
get a can of CRC Mass Airflow Sensor Cleaner from your auto parts store and spray clean your MAF sensor.... a dirty MAF sensor could be causing it as well....
06-10-2013, 01:12 PM #5Originally Posted by 06MonteSS53
Screenshot from today:
- - - Updated - - -
Last edited by Conlan Rose; 06-10-2013 at 09:53 AM.
06-10-2013, 04:22 PM #6
plus, only the front O2 sensors are the ones used for determining the fuel trims... the rear O2 sensors are just used to determine if the cat converters are functioning properly....
the fuel trim parameters you want to look at are called long term fuel trim bank 1 and long term fuel trim bank 2
06-10-2013, 04:41 PM #7
Currently with the free version of torque I can only see the instant trims which seem to switch neg and positive often. What voltage should the rear sensors be at if operating properly?
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