I had the two O2 sensors changed on my Ranger 2002 XL 2.3L, 4 cylinder. I supplied the parts. I bought a Bosch 15716 Oxygen Sensor, OE Type Fitment for the downstream one and a Bosch 15717 Oxygen Sensor, OE Type Fitment for the upstream one.

My mechanic told me that the 15717 didn't appear to be the correct part number for the upstream. He said if check engine light comes on then bring it back and he would swap it out.

Sure enough the light came on. I double checked what I did with the parts and found out that both the 15717 and 15716 were for the downstream.

I was more careful the second time and purchased the Bosch 15664 Oxygen Sensor, OE Type Fitment for the upstream. My mechanic swapped the 717 for the 664.

Damn it all if the check engine light doesn't come on again. I take it to Advance Auto and they plug in their OBD code reader. Sure enough it says the O2 sensor is the code (I believe the front one still but forget). Anyhow, I tell him I just had it changed. He says that if they don't reset the computer correctly, it may continue to set off the check engine light. He asks if I want to reset it using his OBD machine since he can't do it for liability purposes. I go ahead and do it. Check engine light now off.

Next day, damn check engine light comes on again. Truck seems to run fine. Is there a problem with Bosch sensors in Ford trucks? I assume the truck will run rough if O2 sensor is really too blame. What other signs are there of a bad O2 sensor? Is there another way to reset the computer if that is the problem? Or am I missing something altogether?

Thanks

 

What is the code. It is almost useless to ask such questions unless you post the actual code you are getting.

 

I'll get the code and post it. I'm certain it will say upstream oxygen sensor. Sorry if I wasted anyone's time but I thought I was clear in the thread that I had replaced that o2 sensor a second time with the correct part number. Maybe that was not abundantly clear.

 

P0136 - circuit condition (heated oxygen sensor bank 1 sensor 2)
Probably causes -
1 - o2 sensor defective;
2 - fuel system running rich or lean - check other codes first;
3 - engine misfire condition - repair; or
4 - fuel pressure very high or low - fuel pump or pressure regulator.

 

What does that mean?

Essentially the same as P0137, a P0136 code refers to the second oxygen sensor on Bank 1. The O2 oxygen sensor produces a voltage between .1 mV and .9 mV. The ECM monitors O2 sensor voltage and determines if exhaust is lean or rich. O2 sensor voltage is high when exhaust is rich and low when exhaust is lean. The ECM monitors this voltage and increases or decreases fuel injector pulsewidth according to engine fuel/air ratio. If the ECM detects low HO2Sensor voltage for an extended period, it will set P0136 Conditions required to set: HO2 sensor voltage is low for longer than 2 minutes (minutes depend on model of vehicle. Could be up to 4 minutes)
Symptoms

There may be no visible symptoms to the driver. Poor fuel mileage, possible misfire, depending on O2 sensor position when sticking.
Causes

A code P0136 may mean that one or more of the following has happened:

Faulty O2 sensor leak in exhaust close to O2 sensor
Short to voltage on O2 signal circuit
Open in circuit resistance caused by corrosion in connector

Possible Solutions

Replace the second oxygen sensor on bank 1
Repair open or short in signal circuit
Clean corrosion from connector

 

Only thing I can figure is Fords don't like Bosch sensors and maybe I should switch to Motorcraft. Anyhow, at least its not the front sensor and now I know the back one is the problem. I'll switch that out and see.

 

I don't see how you could figure that Ford's don't like Bosch sensors. Bosch makes the Motorcraft sensors, every genuine Motorcraft sensor I have ever seen had either NGK or Bosch inscribed on the sensor. More reasonable logic is that you replaced the sensor, the same code comes back, it means that replacing the sensor did not resolve the problem. Logic dictates the problem must lie elsewhere. Check the wiring and connectors.

 

I originally replaced the sensors as part of general maintenance and not because the check engine light came on. Check engine light only came on after new sensors were installed. Logic therefore dictates that the sensor is most likely the problem unless it was installed improperly which would still be a sensor problem.

 

Ok, then logic dictates that moisture has gotten into a connector, or that the wiring has been damaged in the process. The likelihood of a faulty sensor is fairly slim, assuming the correct part was installed.

You can continue with parts swapping. Hasn't been a successful strategy so far, but hey you could get lucky right?