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11-17-2013, 07:14 PM #1
- Join Date
- Nov 2013
O2 Sensor Problem? Other Problem?
Have a 2005 Suburban 5.3L flex Fuel engine. About 80,000 miles on rig. About two weeks ago it started to misfire. I had run the tank very low and had just filled it up. Always makes you wonder when something starts the next day after that. Well first thing I found out was that the suburban does not have a changeable fuel filter. It finally started to throw codes with a check engine light so I checked them out using a ELM-327 bluetooth OBD-II reader. I was getting P0131: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1) (Powertrain, Generic), P0171: System Too Lean (Bank 1) (Powertrain, Generic), and P0300: Random/Multiple Cylinder Misfire Detected (Powertrain, Generic). I double checked the mass airflow sensor and the air filter. Both looked great and brand new.
By this time, the suburban was starting to backfire and run extremely rich. You could smell gas when it was running. The fact that an O2 sensor was showing a lean condition when excess gas was present indicated to me that the sensor was probably bad. I also figured that issues with the fuel filter would cause errors to both banks equally. Well long story short. I bought a Bosch 15284 O2 sensor to replace the front driver's side sensor. When we put that sensor in, the signal to 0.1 V on both Bank 1 sensors 1 and 2. When we returned the original sensors, 1#1 (bank 1 senor before cat) read at 0.1V while 1#2 (bank 1 after cat) read at 0.1V until the engine was rev'd up then it would go up and come back down as the engine slowed. Still way too much gas. Well maybe both bank 1 sensors were bad so I picked up a Denso 234-4668 O2 sensor. When this is installed it shows 0.1V. We then unplugged 1#2. With it unplugged, it shows 0.44V (which I assume is good that it is reverting to the norm). We then unplugged 1#1. It then showed 0.44V. Still lots of excess fuel being pumped into the system. With both sensors unplugged, the OBD-II reader was not providing fuel trim values. They had been running normal on bank 2 but had been about 25% to 30% on bank 1. Based on the smell, it was at least that bad with both sensors unplugged.
We are now thinking of moving the bank 2 sensors over to bank 1 and vise versa to establish that it is a sensor problem and not a wiring problem on bank 1. However, we are scratching our heads with the gremlin causing the problem. I have only had the rig for about 1.5 months and have put about 3k on it. It has run great both on and off road until now. If we have to take it to a shop, we will, but we are also very competent mechanics. Unfortunately, mechanic is the key word. This is all electronic/computer crap. Any help that people can provide would be appreciated.
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