Hi everyone,
I have been trying to diagnose some intermittent codes on my 2005 Ram 1500 4.7L and am stumped. The truck had been running fine, maybe just a tiny rough on idle, but not enough to cause concern. Then last week the CEL comes on and I get P0151-O2 SENSOR 2/1 CIRCUIT LOW and P0171-FUEL SYSTEM 1/1 LEAN.
I noticed no change in the performance of the truck. I tested the fuel pressure and it was at about 57 PSI, the pressure did bleed off fairly quickly but my gauge was leaking a little. I tried to back probe the O2 sensor but mostly just succeeded in burning my hand.....
I went ahead and cleared the codes. About 100 miles later I get P0175-FUEL SYSTEM 2/1 RICH and P0151-O2 SENSOR 2/1 CIRCUIT LOW. So I went and bought one of those blue tooth scanners to get the O2 voltage and this is where I get confused.... The service manual says that the P0151 code goes off when the O2 voltage is below 2.5196 volts for 3 seconds after starting engine. Well the scanner is saying both of my O2 sensors pretty much stay below 0.6 volts... So why am I only getting a code on one sensor?
This morning I trended the O2 voltage and the 2/1 sensor was reading pretty much zero. Then I cleared the code and as I was driving home I was trending the O2 voltage and the short term fuel trends and the 2/1 sensor bounced between 0 and 0.6 (just like the 1/1 sensor) for about 50 miles (long commute....). Then the 2/1 sensor suddenly drops off and my bank 2 fuel trim shoots to 30% for just a second or two. Interestingly enough this did not throw a code but it did save a freeze frame for what would have been a P0175. but what doesn't make sense is the O2 voltage stayed down and the fuel trim went back to normal. After this trip when I let the truck idle is was pretty rough.
Do you think I should just replace the O2 sensor and see what happens? I really didn't want to start throwing parts at it with it possibly being O2 sensors, injectors, fuel pump etc....
I will attach a screen shot of both of the trends I have referred to.
Thanks in advance for any help!!!

 

I think I got the attachments on here this time.....

 

Sounds like 02 sensors. IMO I would replace them all.

 

I replaced both O2 sensors on the number 2 bank with Delphi sensors. I will probably end up replacing them all just wanted to see if the number 2 bank solved my issues. Well all the codes I was getting (P0171, P0175 and P0151) have gone away and not returned however I am now getting P0155 and P0161 O2 Sensor Heater Circuit Bank 2 Sensor 1 and Sensor 2 respectively. I have searched for a fuse for the O2 sensor heater and can't find one. It's a little hard to believe that both O2 sensors I installed are faulty. What am I missing here?

 

It is possible. No fuse for heater circuit

 

I purchased 4 new 02 sensors from dealership when I did mine, 3 were good and one was bad, so its likely you do have bad ones. my 4 were from the same lot too.