decoding codes

[jocro]

2002 F-150 4.2L 1131 1151 0131 0174 o2 censors but what is bank 1 and bank 2 or where is 1 and 2? Purchased 4 O2 censors not sure all bad.........what next? JOE

[way2old]

Here is short test from manual. The sensors are numbered as follows:
Bank 1 sensor 1 (B1S1) Is on passenger side close to the engine on the exaust. Sensor 2 is after the converter. Bank 2 is the drivers side, same layout.

DTCS P0171, P0174, P1130, P1131, P1150, OR P1151: LEAN SYSTEM DTCS
Note: Do not clear the DTCs or reset the keep alive memory (KAM).

Fuel System and HO2S DTC Reference List:

Bank 1 = DTC P0171 (lean)
Bank 2 = DTC P0174 (lean)
HO2S-11 = DTCs P1130 and P1131
HO2S-21 = DTCs P1150 and P1151
Access and record the ECT PID from the freeze frame data. The freeze frame data will be used to recreate the concern.
Retrieve and record the self-test DTCs.
Are any DTCs present other than P0171, P0174, P1130, P1131, P1150, or P1151?
Yes
DISREGARD the current diagnostic trouble code (DTC) at this time. GO to Section 4, Diagnostic Trouble Code (DTC) Charts and REPAIR the other DTCs.

P0131

CHECK FOR SOURCE OF POTENTIAL HO2S CONTAMINATION
Investigate the following items as potential sources of HO2S contamination:
Use of unapproved silicon sealers.
Fuel contaminated by silicon additives.
Excessive oil burning (i.e. rings, valve seals and oil overfill).
Glycol (antifreeze) leaking internally in the engine.
Lead contaminated fuel.
Short drive cycles in cold weather.
Use of unapproved cleaning agents.
Were any of the above conditions or concerns found during inspection?
Yes No
REPAIR source of contamination. REPLACE HO2S and oil/filter. COMPLETE PCM Reset to clear DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2, Drive Cycles). If diagnosing DTC P0141 or P0161, GO to H30 . All others: REPLACE PCM

[serge_saati]

Originally Posted by jocro

2002 F-150 4.2L 1131 1151 0131 0174 o2 censors but what is bank 1 and bank 2 or where is 1 and 2? Purchased 4 O2 censors not sure all bad.........what next? JOE

Bank 1 is for right (rear) exhaust manifold hose of engine. Bank 2 for left (front) side of engine.

1st O2 sensor is the one upstream (between engine and Catalyst)

2nd O2 sensor is downstream (between catalyst and exhaust pipe)

The P0174 is for system too lean, bank 2. It's not caused by O2 sensor, but a vacuum leak or something else that cause to run too lean, such bad front fuel injectors.

The 3 other codes are for bad O2 sensors. You need to replace the 2 upstream O2 sensors.

[mechanic1980]

did you change the air filter or open the air box because a loose air box will cause these codes to and even cause stalling because air is coming in after maf sensor so the computer doesnt know why its lean when the air in measured is right but the end result is wrong

[jocro]

replaced front two O2 sensors yesterday, got two codes today....0171 0174. Does the engine have to run a few days to settle in? Looks like too lean bank one and bank two. Looked for bad vacumn lines but did not put a gauge on it. Will hook up vacumn tester tomorrow. Any more thoughts deeply appreciated. Thanx.....JOE

[serge_saati]

usually, 171/174 codes on big ford engine are caused by vacuum leak on the upper intake manifold. Original isolator bolt also need to be replaced.

Or it can be resulted by a bad MAF sensor, but it's more rare. Sometime it just need to be cleaned a little bit.
Dirt MAF is a rare cause too.

[jocro]

update..............first, thanks to all for your help.................My son replaced the upper intake manifold gaskets...............the round ones I think.........and all is well. Two o2 sensors and the gaskets got the job done. thanks again..............JOE

[yotermanic]

I gotta pipe up and say the upstream O2 sensors probably weren't bad, but the vacuum leak caused the codes in the first place. Oreilly's and Advance started an urban legend when they were scanning cars that O2 sensors frequently go bad, and I'm doing what I can to combat it. DO NOT REPLACE O2 SENSORS WHEN BOTH BANKS BEGIN READING LEAN AT THE SAME TIME!!!! "They've been fine for 150,000 miles, now they both went out in the last seven minutes...what a coincidence."

[serge_saati]

Originally Posted by yotermanic

I gotta pipe up and say the upstream O2 sensors probably weren't bad, but the vacuum leak caused the codes in the first place. Oreilly's and Advance started an urban legend when they were scanning cars that O2 sensors frequently go bad, and I'm doing what I can to combat it. DO NOT REPLACE O2 SENSORS WHEN BOTH BANKS BEGIN READING LEAN AT THE SAME TIME!!!! "They've been fine for 150,000 miles, now they both went out in the last seven minutes...what a coincidence."

But you forget to consider P1131 & 1151 codes, which indicate O2 sensor heating circuit malfunction. The heating coils inside the sensors were damaged.