1997 Explorer SOHC code P0174

[allmyEXes]

On my Blue '97 I'm having a recurring DTC P0174. That is system too lean on bank 2. How would I determine if the problem is an O2 sensor and which of the 2 on the right side? Thanks for any input anyone has.

 

[donalds]

I'm not sure how to do it without a good scan tool
Or Forscan

I'd try a smoke test and look for vacuum leak

You can DIY a smoke tester
Bank two is passenger side

 

[allmyEXes]

I've leaked check as recent as two years ago when I re-did the entire intake manifold set. I do have the Innova 3100 hand held. I'm not sure how to use it other than to read codes on it.

 

[donalds]

Yes I'm pretty sure your Innova 3100 can test o2 sensors
You will find videos on YouTube on how to do it

 

[J_C]

I hate the idea of firing the parts cannon but in this case if your O2 sensors are original, it seems timely to replace the upstream sensor.

Watching live data on a scan tool would definitely be useful. If the fuel trims lower significantly with increasing throttle, more likely a vac leak, but if you haven't cleaned your MAF sensor in a while, I'd try that too.

 

[C420sailor]

Don’t the upstream determine A/F ratio and the downstream monitor catalytic converter efficiency?

 

[donalds]

Don’t the upstream determine A/F ratio and the downstream monitor catalytic converter efficiency?

Yes sir

 

[allmyEXes]

Thanks, so far y'all. Does the 1997 4.0 SOHC have heated oxygen sensors?

 

[RickOTR]

Yes they do> What about those plastic vacuum hoses?

 

[donalds]

The fact that you are getting the code says the sensor is working
How well. The data can only show that

 

[allmyEXes]

Studying how to use the Innova 3100, and looking for a 50 HP air compressor for work for media blasting.
?? For no money could someone swap the L and R upper O2 sensors, clear the pcm and cause it to post a DTC of P0171 ? To determine if it has one bad (EDIT-Faulty) O2 sensor?

 

[J_C]

It looks like on the Innova 3100, from the main menu you choose System Tests, then OBD Monitor Test, then it will list the O2 sensors and should give a live update with engine running.

Swapping the sensors seems like extra work to me, I mean if you're going to take them both out then I'd just replace them both, but yes you could do that. In theory if they are bad enough to be near needing replaced, you may also gain a little fuel economy from doing so. You might also want to check the spark plugs on that engine bank, in case it's started burning oil and this accounts for the O2 sensor getting fouled.

 

[drdoom]

Years ago on my '97 SOHC I had same code, ended up pulling the sensor and check with multimeter & propane torch...passed the test a couple times, then I tested it once more and caught it acting up. Replaced and good to go.

 

[allmyEXes]

I would think that if it was a general engine vacuum issue then I would get a DTC for both sides of the engine.
If it were a vacuum leak from a leaking intake runner I would expect a one sided type of reading. Right at two years ago I installed a complete FELPRO set and I'm absolutely sure that I didn't have any install issues.
As far as getting under the vehicle to swap used O2 sensors as a way to determine if the sensor is bad I'm too old for that. I'll do good to install one new one if I can get up under it.
I'll try that with the INNOVA 3100 this weekend to get a KOER readout on it.
Thanks guys.

 

[DemonMudder]

Well I hope yours ain't like my '99, it recurred on mine for the longest time and I finally figured out that it's a leak in the intake manifold gasket. So I'm replacing that in a week or so, depends on when the parts come in. Hopefully yours is as simple as the O2 sensors, mine had to be a pain

 

[jammor]

Well I hope yours ain't like my '99, it recurred on mine for the longest time and I finally figured out that it's a leak in the intake manifold gasket. So I'm replacing that in a week or so, depends on when the parts come in. Hopefully yours is as simple as the O2 sensors, mine had to be a pain

Mine was intake manifold gasket as well. Very important to get good quality gaskets and install and torque properly. And if you can't torque it properly make sure you torque the hell out of it. You might be able to fix it by tightening what's on there- definitely just bite the bullet and replace O2 sensors and spark plugs if they are old. I eventually did my injectors but that was due to P0304---- Smoke test first sounds good too...

 

[allmyEXes]

Fixed it. It was the O2 sensor closest to the RH exhaust manifold.

 

[CDW6212R]

That's the best result. The lean code can be from several things, the O2 sensors are the easiest to do.

My 99 had the P0174 rarely, but finally it did it at high speed(I noticed a loss of power and then the light came on). I had tested fuel pressure about four times before then, it had enough until after the highway issue. Then I only had 52psi or so, it was the fuel pump rubber hose, one had a split in it, it was leaking fuel. So it cost a pump for about $50, plus the labor to R&R the tank.

 

[DemonMudder]

Mine was intake manifold gasket as well. Very important to get good quality gaskets and install and torque properly. And if you can't torque it properly make sure you torque the hell out of it. You might be able to fix it by tightening what's on there- definitely just bite the bullet and replace O2 sensors and spark plugs if they are old. I eventually did my injectors but that was due to P0304---- Smoke test first sounds good too...

Haven't had that code before, but yeah, I already replaced the O2 sensors, fuel filter, alternator, etc.. anything to fix my rough idle lol

 

[allmyEXes]

By the way, thanks again guys!