I have a 99 motorhome on a f550 ford V10 chassis. On 2 short camping trips now, I have gotten the service engine light, and a code of 1131 on the return trip home. The engine is running great, and has no miss, hesitation or any reason to thing anything is wrong other than the light and code. Any ideas??? Actually, any ideas that dont include a trip to a Ford dealer and a huge hole in my wallet??? Thanks

 

Chk to see if this vehicle has o2 sensors .If it was a p1131 dtc code it indicates a failure in the heater for the o2 sensor or a voltage switching at the sensor feedback to the pcm.
Rich

 

Yes, it has all the standard gear of a ford F550 or F53 motorhome chassis. I can see O2 sensors in the exhaust pipes just below where the come off the exhaust manifolds on both sides.
So, do you think I should just replace the bank 1 sensor (code says bank 1, p1131)? I am told bank 1 is the passenger side. Is that correct?
Thanks again.
Lee Bates
'99 bounder 34V

 

Lee

It is Ok to replace one at a time .... but the typical O2 sensor gets weaker and slower with age... when one fails the other is usually not too far behind, in my experiance

I always replace them in pairs... I am not every looking forward to putting in 4 new ones in my current truck, but they are an important enough component to the proper air fuel mix that I will when the time comes

 

I'm with Fred ,I change both at the same time ,they should be about $60 apiece .
Make sure your wiring going to them looks okay before buying new o2's it can be burned wiring also.
Rich

 

P1131 is almost always the sensor. UPSTREAM on the passenger side. P1151 for the driver's side. Neither code has anything to do with the heater circuits.

Fred, It makes absolutely no sense at all to replace all four sensors. The downstream ones are not used for A/F control, they are only there to see if the cats are working.

Personally, I only replace O2 sensors when there is an indication they're at fault. If it makes you feel better to replace them in pairs, it's your money.

Steve

 

Thanks everyone for the info. Will probably replace the passenger side upstream one first.....then see what happens next trip, the end of october. It will be a short one too, so not harm in a test run. Thanks again. I will let you know if it fixes the recurring code "1131".

 

projectSHO89

If I know what the 4 O2 sensors on my 3v V10 6.8L are designed to do, and how they do it. AND I have experience with how O2 Sensors typically fail. AND I have a desire for my equipment to operate the way it is intended to operate... it seems logical for me to conclude that I might some day need to consider replacing all 4 of my O2 sensors at the same time

If some how "It makes absolutely no sense at all to replace all four sensors" can be explained in a tad more detail, perhaps I can save some money and time about 70,000 miles from now

BTW...I fully understand every thing in the OBD I and II description and theory I posted below. Including the rest of the 130+ pages of data for 2005 ODB II implementation , diagnostics, and calibration as it ralates to my Ford 3v V10 powered truck.

Some in here may be interested in the last paragraph where alcohol blend fuels are discussed

In an effort to not be stuck on stupid, I spend a fair amount of time on my personal education.

From the Motorcraft technical info site (link at bottom of page):

The Catalyst Efficiency Monitor uses an oxygen sensor before and after the catalyst to infer the hydrocarbon efficiency based on oxygen storage capacity of the ceria and precious metals in the washcoat. Under normal, closed-loop fuel conditions, high efficiency catalysts have significant oxygen storage. This makes the switching
frequency of the rear HO2S very slow and reduces the amplitude of those switches as compared to the switching frequency and amplitude of the front HO2S. As catalyst efficiency deteriorates due to thermal and/or chemical deterioration, its ability to store oxygen declines.

The post-catalyst HO2S signal begins to switch more rapidly with
increasing amplitude, approaching the switching frequency and amplitude of the pre-catalyst HO2S. The predominant failure mode for high mileage catalysts is chemical deterioration (phosphorus deposition on the front brick of the catalyst), not thermal deterioration.

All applications utilize an FTP-based (Federal Test Procedure) catalyst monitor. This simply means that the catalyst monitor must run during a standard FTP emission test as opposed to the 20-second steady-state catalyst monitor used in 1994 through some 1996 vehicles. Two slightly different versions of the catalyst monitor are used
for 2001 MY and beyond vehicles. Both versions will continue to be used in subsequent model years. Switch Ratio Method (1996 - 2005)
In order to assess catalyst oxygen storage, the monitor counts front and rear HO2S switches during part-throttle, closed-loop fuel conditions after the engine is warmed-up and inferred catalyst temperature is within limits.

Front switches are accumulated in up to nine different air mass regions or cells although 3 air mass regions is typical. Rear switches are counted in a single cell for all air mass regions. When the required number of front switches has accumulated in each cell (air mass region), the total number of rear switches is divided by the total number of front switches to compute a switch ratio. A switch ratio near 0.0 indicates high oxygen storage capacity, hence high HC
efficiency. A switch ratio near 1.0 indicates low oxygen storage capacity, hence low HC efficiency. If the actual switch ratio exceeds the threshold switch ratio, the catalyst is considered failed. Index Ratio Method (some 2001 and beyond) In order to assess catalyst oxygen storage, the catalyst monitor counts front HO2S switches during part-throttle, closed-loop fuel conditions after the engine is warmed-up and inferred catalyst temperature is within limits. Front switches are accumulated in up to three different air mass regions or cells. While catalyst monitoring entry conditions are being met, the front and rear HO2S signal lengths are continually being calculated. When the required number of front switches has accumulated in each cell (air mass region), the total signal length of the rear HO2S is divided by the total signal length of front HO2S to compute a catalyst index ratio. An index ratio near 0.0 indicates high oxygen storage capacity, hence high HC efficiency. An index ratio near 1.0 indicates low oxygen storage capacity, hence low HC efficiency. If the actual index ratio exceeds the threshold index ratio, the catalyst is considered failed.

General Catalyst Monitor Operation If the catalyst monitor does not complete during a particular driving cycle, the already-accumulated switch/signallength data is retained in Keep Alive Memory and is used during the next driving cycle to allow the catalyst monitor a better opportunity to complete, even under short or transient driving conditions.

Rear HO2S sensors can be located in various ways to monitor different kinds of exhaust systems. In-line engines and many V-engines are monitored by individual bank. A rear HO2S sensor is used along with the front, fuel control HO2S sensor for each bank. Two sensors are used on an in-line engine; four sensors are used on a V-engine. Some V-engines have exhaust banks that combine into a single underbody catalyst. These systems are referred to as Y-pipe systems. They use only one rear HO2S sensor along with the two front, fuel-control HO2S sensors. Y-pipe system use three sensors in all. For Y-pipe systems, the two front HO2S sensor signals are combined by the software to infer what the HO2S signal would have been in front of the monitored catalyst. The inferred front HO2S signal and the actual single, rear HO2S signal is then used to calculate the switch ratio.

FORD MOTOR COMPANY REVISION DATE: DECEMBER 2, 2004 PAGE 5 OF 131
Most vehicles that are part of the “LEV” catalyst monitor phase-in will monitor less than 100% of the catalyst volume – often the first catalyst brick of the catalyst system. Partial volume monitoring is done on LEV and ULEV vehicles in order to meet the 1.75 * emission-standard. The rationale for this practice is that the catalysts nearest
the engine deteriorate first, allowing the catalyst monitor to be more sensitive and illuminate the MIL properly at lower emission standards.
Many applications that utilize partial-volume monitoring place the rear HO2S sensor after the first light-off catalyst can or, after the second catalyst can in a three-can per bank system. (A few applications placed the HO2S in the middle of the catalyst can, between the first and second bricks.) Index ratios for ethanol (Flex fuel) vehicles vary based on the changing concentration of alcohol in the fuel. The
malfunction threshold typically increases as the percent alcohol increases. For example, a malfunction threshold of 0.5 may be used at E10 (10% ethanol) and 0.9 may be used at E85 (85% ethanol). The malfunction thresholds are therefore adjusted based on the % alcohol in the fuel. (Note: Normal gasoline is allowed to contain up to 10% ethanol (E10)).

All vehicles employ an Exponentially Weighted Moving Average (EWMA) algorithm to improve the robustness of the FTP catalyst monitor. During normal customer driving, a malfunction will illuminate the MIL, on average, in 3 to 6 driving cycles. If KAM is reset (battery disconnected), a malfunction will illuminate the MIL in 2 driving cycles. See the section on EWMA for additional information.

The full text can be found at: http://www.motorcraftservice.com/vdirs/diagnostics/pdf/OBDSM505.pdf

 

projectsho89
Well it must be that all the manuals I've ever read are wrong then for the p1131 code !
Then.
If you have used a good scanner and monitored a o2 sensor feedback to the pcm you will see a difference from older o2 sensors versa's newly installed sensors.
As stated in fred's explanation directly from Ford they become coked or insulated therefore don't read properly.
Rich

 

I do driveability work at a dealer and have never had to replace all 4 o2 sensors for just one code, the definition of the code would be something like o2 sensor bank one sensor one lack of switching indicates rich or lean, something of that sort. So why would you replace all 4 especially considering that the "downstream o2's" only monitor the operation of the catalists. What you have posted is totally true and if read and comprehended correctly you also would conclude that you do not need to replace all 4 o2 sensor to correct the problem. I have personally dealt with this code numerous times, replaced the o2 sensor at fault and haven't had any come back with the same concern. Finally, I did not type this to undermine or call anyone stupid, I'm just trying to save a fellow ford truck owner a little money.

-Ryan

 

Jesus.......I didn't mean to start a bar brawl!!!!! Next time, I'll write to ANN LANDERS or something!!!!

 

Yes you did, admit it!!!!!!! HE he he !
we are entertaining

Hope things work out !

projectsho89 is correct about the heater circuits though ,I was going from memory ,I just reread the code description .
But I always change both upstream bank 1 and bank 2 when one side fails.This tends to keep the fuel trims balanced.


Rich

 

Well ryans 428
You are talking from a dealer tech perspective while I am talking from an experience with my own vehicles perspective...I assume you mostly see O2 sensors that fail early.

I have a little experience with high tech computer controlled motors from as early as my 1976 Datsun 280ZX, 81 280ZX, 84 300ZX and a 86 300 ZX Twin turbo twin intercooled super car I bought in Germany and had professional tuned by and AMG type company. My wife had a German Ford XR4II that would whoop my Z cars *** all day long on the A-bahn and wink wink my Z car would do 258KPH ! (159MPH). Yep it was computer controlled too....Included in my experience are most of the 79 and up model Ford and Chevy BB trucks, Carb and EFI 460 and 454 v8s.

We had 2 BMW and a Mercedes along with a 2000 Ford Escort ZX2 I still have that is tuned pretty damned hot. Also a Volvo, 3 VWs, 2 Audis, a Jeep CJ7, and a Crown Victoria...... On the last 18 cars and trucks I have owned I, my wife, and my son do the maintenance, modifications, and management. (Daughters just sits around looking good and managing to put most of the dings on the machines)

Of interest some here might note that my family has had several vehicles from 1975 to present that got well over 300,000 miles with no rebuilds... my wife and I put almost 400K on a 71 Toyota Corolla, we had a used 77 VW Golf diesel that went 378K, my 1986.5 Nissan truck is still on the road in town with over 390K on the clock and still starts first flip every time

The 86 Z car and the 01 F250 and this 05 F350 are the only brand new vehicles I have bought....all the other cars were used and a few of them were cheap basket cases that I resurrected. Most were butt ugly

You might say I have a little bit of O2 and computer control vehicle experience

My experience is with O2 sensors that have gone the 70,000 to 90,000 expected life span....In the past I have tried to cut the corner, change the one bad sensor, and reset the CEL... experience proved on more then one vehicle from more then one manufacture that ultimately the other sensor(s) fails shortly thereafter....

On pre 2005 V10s I think the issue is not as critical as on the newer versions. And certainly as Ford moves the PCM diagnostic programing to control more and more of the POWER TRAIN in an effort to give perfect drivability, comply with stricter and stricter EPA and CAFE standards, and support the warranty requirements on the emissions systems, there will be more need to replace components in pairs to maintain the calibration and balance

BTW did you notice that the gentleman who asked the question has a 99 F550 chassis motorhome... age and the nature of the sever duty of his machine suggest to me that his O2 sensor (s) are not faulting due to manufacture defect or corrosion... they are at end of their life expectancy...IMO

Now to make all you folks who don't read for comprehension feel good... if my 2005 3v V10 with a scant 30,000 miles was to fault for an O2 sensor right now, and Ford diagnosed and replaced only one of them, I would not be jumping up and down demanding all 4 be replaced...

I would be confident that just that one was defective and failed early.....

But a completely different story at the 75,000 mile or higher milage...then I would most certainly bite the bullet and put 4 new $60-$90 replacement O2 sensors in, and chalk it up to normal maintenance... anyone who expects an O2 sensor to last the life of a modern vehicle is fooling them selves

Best I have seen in last twenty years are the Bosh units that are good for about 100K and even they can fail early at the 80-90K range due to excessive rich conditions from folks who have changed the factory command settings (modified the motor) or let the engine get way too far out of proper maintenance intervals.

 

Top,

Not trying to start any pi$$ing contest with you. But, replacing the downstreams at the same time as the upstreams is an extra expense that cannot usually be justified from either an expense or emissions standpoint unless there are indications that it is need.

We both have a lot of experience. Me, I spent seven years as a 27B. Followed that with a stint with Hughes at Ft Hood as the LAO for the TOW system on the Bradley back in the mid-80s then ran their DRF for a year. FWIW, lived in CC and Kempner while I was at there. Spent last 20 years after that doing commercial electronics. I have a very good understanding of the OBDII system and already have all the Ford docs.

When I come across a lazy/weak upstream O2 sensor on a two-bank engine, I always look at the output of the other one on a graphing scan tool (computerized). If it is switching cleanly, I can't justify the expense of replacing it. If it is erratic or noisy, it gets replaced. A little diagnostic work can indeed go a long way.

I also try not to get stuck on stupid (I loved hearing that general telling that reporter off). However, it's also important not to get stuck on stubborn.


Rich,

I see nothing in the above quote that mentions anything about "As stated in fred's explanation directly from Ford they become coked or insulated therefore don't read properly." Where did the Ford doc mention this regarding O2 sensors?

Steve

 

Hey Steve not stuck on stubborn either

I get what you are saying... and agree with it for new vehicle within warranty....BUT....folks with 7 year old or older vehicles or high mileage may be better served to spend $60-$90 X 2 (or even X 4) as a prophylactic exercise then spend $75 to $629 for a Ford technician to do a diagnostic test, drive-ability test, and then test an individual component.... and then maybe still have to replace the component(S).... for the $60-$90 plus labor....

Shall we discus my bill from the Killeen Ford dealer on exactly this issue on my daughters 2001 Ranger... that at 60,000+/- miles was acting weird (daughters description) CEL, hard start, dies at lights, poor fuel economy. Out of warranty

I was out of country, wife tells kid to take it to the dealer.....( I buy all my new vehicles from Cove Ford and personally know every person on the service staff) silly daughter drops it off at the Killeen dealer who does a diagnostic, replaces a part, no fix, re test, replace another part, no fix, replace catylitic and O2 sensors... $679 bill...paid by wife over phone...

I get back three days later, hear the story, get the ***.....I went into the Killeen service department and asked head manager to explain this process... (a master tech (that I know at Killeen Ford) tells me that he originally told the servicing tech to start at the cat and O2 sensors (experianced based diagnosis))... I relate this to the service manager who does a little investigation and reduces bill to $256 for a cat and O2 sensors...

I am savvy enought to loudly complain to the Ford Regional rep who got me a refund of the $265 based on my argument that the diagnosis and repairs of emissions related is mostly covered by the 8/80,000 clean air act requirements

Come on Steve...my advice to the original poster was that it was OK to just replace the one... I went on to describe how I would do it on my current truck if and when the time comes... and I seem to be taking a lot of flak for the notion that I would simply replace all 4 sensors.... we are not talking expensive or labor intensive parts here