I have a 98 4.0 Ranger. Recently my CEL came on so I pulled the codes which came back P0153 (bad o2 sensor: bank 2, sensor 1). I replaced the sensor, reset the codes and was good for a few days, until the CEL turned back on. Pulled the code and got the same result... P0153. What's going on here? Do I have a bad electrical connection? I've read that dialectic grease should never be used on o2 sensor plugs. Is there something else I can try? Any info is appreciated. Thanks guys.

EDIT: Also, the dude at Autozone who sold me the new o2 sensor told me it was the upstream sensor on the passenger side. Is this correct? I've found conflicting info saying that it is on the driver's side...

 

The dude at AZ is wrong. P0153 code implicates the driver's side upstream 02 sensor.

 

That chaps my a$$ and is another reason why I usually get my parts from O'reilly. I guess that's what I get for not double checking with my repair manual first. Looks like I'll be replacing that sensor tomorrow. Might as well clean my MAF while I'm at it too. Can a bad PCV valve trip that code? The truck has 175k on it so I'm thinking there could be several contributing factors. I may go ahead and replace the PCV valve too considering how cheap they are.

 

Most 02 codes have to do with lean or rich conditions. P0153, on the other hand, is more often either a hardware-related problem (02 sensor is bad) or a circuit-related problem (short/open in 02 wiring). If it's within your budget, you're probably better off just leaving the new 02 sensor on the passenger side, and replacing the one on the driver's side.

Go ahead and clean the MAF and change out the PCV valve (I recommend a Motorcraft PCV valve, they seem to fit better on mine...).

 

Most O2 sensor codes have nothing to do with rich or lean conditions. The O2 sensor codes are set when the sensor has something wrong with it. The rich and lean codes are something different and replacing the sensors to resolve rich or lean codes almost never fixes the problem.

At you mileage, the sensors should have been replaced twice already.

Just so you know, for Fords and most imports, both Japanese and European, the Bank#1 is the passenger side and bank two is the divers side on RWD models. For FWD, Bank#1 is the firewall side and Bank#2 is the radiator side.

The exceptions are GM vehicles, some of the Chryslers, and a few others here and there.

 

Then what would you call P0171, P0172, P0174 and P0175? It's through 02 sensor signal feedback that the system knows whether the engine is running lean or running rich, and the aforementioned codes are seen far more often then any other codes having to do with the 02 sensors.

 

P0153 is for slow response of the bank-2 (drivers side) upstream O2 sensor.

With the mileage on this ride I agree with changing Both O2 sensors, as their response time slows (gets lazy) with age, sorta like me!!!! lol

Most folks change them around 75-100K miles.

Be sure to use some high temp nickel anti-sieze compound on the threads if they don't come with it applied. Careful not to get any on the sensor end & contaminate it.

If your also going to clean the MAF sensor, remove it for a careful cleaning after it's cooled down & be sure to use a non residual plastic safe cleaner like CRC MAF Sensor spray cleaner. Don't touch the sensor with the wand & keep the sensor squeeky clean on installation, so it's not contaminated & have it's PID to the computer corrupted.

You might pull the B- battery cable while your doing all this, to wipe the computers memory, so it can begin to build new fuel trim tables with the cleaned MAF sensor & new O2 sensors in place.

If you have an auto tranny, after the repairs & to aid the vehicle in relearning it's cold & warm idle strategy & maybe avoid some driveability problems, turn off all electrical loads, reattach the B- battery cable, start the engine & let it idle down some, then shift into All gears ending in "N" or "P" & let it sit idling without touching anything, or turning anything on while the engine fully warms up, then shift into all gears again.

Then do some stop & go driving, then some highway driving & by then the computer should have relearned enough that driveability should be ok, while it relearns the remainder of what it needs too know.

More thoughts for consideration, let us know how it goes.