Code P0174 P0171 P1131 P1151 in 2003 Ford F-150?

Answer 1

P0174 OBD-II Trouble CodeTechnical DescriptionSystem Too Lean (Bank 2) What does that mean?Basically this means that an oxygen sensor in bank 2 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines

, Bank 2 is generally the side of the engine that doesn't have cylinder #1.

Note: This DTC is very similar to P0171, and in fact your vehicle may show both codes at the same time.

--------------------------------------------------- P0171 OBD-II Trouble Code

Technical DescriptionSystem Too Lean (Bank 1) What does that mean?Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.

Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time.

------------------------------------------ P1131 OBD Trouble Code= Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1 =

------------------------------------------ P1151 OBD Trouble CodeNOTICE: The information contained on this site is presented for information only. OBD-Codes.com is not responsible for any actions you take on any vehicles. If you have any doubt as to repairs on your vehicle, please contact a qualified technician.

Technical DescriptionLack of HO2S-21 Switch, Sensor Indicates Lean What does that mean?A Heated Exhaust Oxygen (HO2S) sensor indicating lean at the end of a test is trying to correct for an over-rich condition. The test fails when the fuel control system no longer detects switching for a calibrated amount of time.

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Oxygen Sensor

If you look inside the wheel wells behind the fender liner, right about where the frame is one O2 sensor, the other is underneath the truck about half way back in relation to the transmission. If you see where the exhaust joints together, you went about 6" too far.

When you start looking at the O2 sensors, they are normally numbered something like "Bank 1 Sensor 1" Bank 1 is on the passenger side; Bank 2 is on the driver's side. Sensor 1 is the upstream sensor (near the frame, between the block and the cat) and Sensor 2 is near the Y-pipe (downstream of the cat).

Normally it is the upstream sensors (sensor 1) that go first. They see the harshest conditions.

You will need;

Oxygen Sensor Socket

Anti-Seized

Penetrating Oil

Sometimes it will take 15 minutes or take a few hours it depends on your luck…

Okay, here's something else to consider for an aging F150, maybe other Ford products too? The AIRB or AIR BYPASS RELAY (SOLINOID) ages as does its counterpart the Diverter Relay. They are the same part and are hard to find let alone diagnose. The ERG relay is right next to both of these, at least in a 1996 PU.

SO, here was my problem: I could not get the diverter valve and the bypass air valves to coordinate properly. The bypass has to "know" to open and close in a rhythm like a heart beating. On my F150 the two valves are one part together where the air pump connects as well as the feed to the exhaust manifold.

If the diverter is not functioning, it'll cause a P0411. It may get a P0171 with it for a 6 cylinder. If you put pure vacuum on the diverter (both valves) then the darned P0171/174 combo will come up and the MIL is right back. The engine will run with a pure vacuum on both valves but may stall at idle. Note: EGR should have no vacuum going to it at idle. If it does, start there as you are basically chasing a vacuum problem, unless you have many other codes. Check or replace the DPFE sensor that operates the EGR, if you have one and you should. Just find it.

After doing everything in sight I finally touched on the idea of tying the EGR and the vacuum line to the diverter valve together using a Y connector. It worked. Not only did the P0411 go away but also the P0171 and the pesky come-and-go P0174. These say too lean a mixture. Bank 1 means cyl 1-3 in a straight 6.

The books say all sorts of things about the 171/174 situation including replacing the valve cover gasket. Guess what? Mine was loose so I merely tightened it. It's difficult to reach the rear bolts with the engine assembled. Do what you can reach, gently! Make sure everything is tight and as close to torque as possible. Check the PCV valve and its hose.

One other thing: To help ensure that the engine would pass smog tests, I put 92 octane gas in it for a few days. That's just a small insurance policy. My MIL has stayed off. I'm not able to further diagnose why the darn AIRB relay is not totally working. The problem is that another vac line leaves it and I was concerned about touching a relay or line I could not get a part number for. Those cheap plastic vac lines don't age very well. It was NOT a fuel pressure problem.

Heaven only knows what I'd have been charged at a repair shop? I figure they'd have said "it's the head" or worse. That'd been $1400 in CA priced labor right there! Keep at your fix. You can do it! I did. It just took two weeks to experiment with the engine. Spray silicone on all exposed rubber elbows from time to time. That'll keep them from cracking. My F150 has 279k on it. So far, I've not had to mess with the fuel pump. Those fuel filters last almost forever too.