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1131 Code, changed oxygen sensor, code still comes up.

SvtBob

New CEG'er
Joined
Jan 1, 2007
Messages
10
Hi Gang,

Originally I was flashing a 0133 code and an 1131 code.

I replaced the Upstream bank 1 O2 sensor ( by the firewall ) . Which was time consuming but not bad because I bought the right tools as stated on the forum before I tackled the job.

I reset the CEL and drove it for a few days and eventually the CEL came back on. I went and got the code checked again and now it shows an 1131 code but the 0133 code is gone.

Any clues as to what may be giving me the 1131 now that I have replaced the sensor?

also the idle is a little rough and has been rough ever since I originally a few months ago started getting the Check Engine Light.

Thanks gang,

Bob
1999 Contour SVT
 
From TSB, go through the cheap and easy ones first.

P1131 - Lack of HO2S-11 Switch, Indicates Lean.

When an HO2S sensor indicates lean at the end of a test, the system is trying to correct for an over-lean condition. The code is set when the fuel control system no longer detects switching for a calibrated amount of time.


Electrical

· Short to VPWR or VREF in harness or HO2S
· HO2S circuit shorted to Ground
· Water in harness connector
· Open circuit
· Corrosion or poor mating terminals and wiring
· Damaged HO2S
· Damaged PCM (other DTCs should be present)

Fuel System:
· Excessive fuel pressure (stuck fuel pressure regulator, restricted fuel return lines, etc.)
· Leaking/contaminated fuel injectors or fuel pressure regulator
· Low fuel pressure or running out of fuel (fuel pump concern, fuel supply line restrictions, low fuel level, etc.)
· Vapor recovery system (stuck VMV, etc.)

Induction System:
· MAF contamination
· Air leaks between MAF and throttle plate
· PCV system / Other vacuum leaks
· Improperly seated engine oil dipstick

EGR System:
· Leaking gasket
· Stuck EGR valve / Leaking diaphragm or EVR

Base Engine:
· Oil overfill
· Incorrect cylinder compression
· Exhaust leaks before or near the HO2S
· Secondary air stuck on

Edit. "also the idle is a little rough and has been rough ever since I originally a few months ago".
Check for vacuum leaks first.
 
Tony 2005 - Thanks for the information. My youngest son has a 98 Contour and called to say his CEL came on. Scanner indicated P1131. The only thing that I could find was that only one of the five clips that hold the air cleaner box lid on were snapped - hence extra air. Hope this solves his challenge with the CEL. I turned the light off and will check again in a few days.

From my scanner the 02 sensor readings seemed within tolerance so went looking for the "dumb stuff". He recently had his oil changed so who knows.

Russ
 
This is getting curiouser and curiouser. Cleaned the MAF, reattached all of the clips on the air filter housing clips and turned off the CEL. A week later the CEL is back on with P1131 again. So I scanned everything and oddly enough the readings for the O2S 1 1 (upstream) vary from .085 to .175 while the readings for the 02S 1 2 (downstream) stay steady at .785. Must have an O2S getting sick. Any confirmation?

Thanks

Russ
 
The lower (downstream) sensor is fine. Don't mess with it.

As for the upstream sensor, is this what you did?

"With the HO2S connected and engine running, measure the voltage with a Digital Volt-Ohmmeter (DVOM) between terminals HO2S and SIG RTN (GND) of the oxygen sensor connector. Voltage should fluctuate between 0.01-1.1 volts. If voltage fluctuation is slow or voltage is not within specification, the sensor may be faulty." Autozonelink

http://www.autozone.com/az/cds/en_us/0900823d/80/1b/ca/83/0900823d801bca83/repairInfoPages.htm

And did you check the connector as well as the wiring for the O2 sensor? As it is near the Bank 1 Exhaust manifold, the insulator may have got "nicked" when you installed the new Bank 1 (firewall side) Upper O2 sensor.
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=v6maint&Number=1023736&Forum=v6maint&Words=replace%20o2&Match=And&Searchpage=0&Limit=2500&Old=allposts&Main=1023736&Search=true#Post1023736
 
Last edited:
Thanks for your replies. I was using my scanner and not a DVOM. I did replace the O2 Sensor upstream of the catalytic converter and we are in the process of driving the car to relearn the new device. The readings that I get on my scanner from the new sensor compared to the old one are very different.

I have not been able to locate any vacuum leaks however if there are certain known weak spots I would appreciate knowing about them so I can look again.

BTW my car is a 2.0 l 4-cylinder so the O2s was in front and the connector is attached above the radiator. No signs of any discoloration or other wear/tear. Connector was nice and clean inside. The old O2 sensor was original Ford and the car has 123,000 miles. Should have been changed at 100 k from what I understand.

Russ
 
There is no specified change interval.

Although I believe in aggressive maintenance, I saw no need to change mine until it started acting up which didn't happen until well past 200,000 miles.
 
Duh, how do you turn off the CEL?

Duh, how do you turn off the CEL?

I know this might sound ignorant, but how do you reset the CEL?
 
I have a 98 SVT 2.5 V6, MTX. Am getting intermittent dct P1131. At times the car "heals" itself and CEL goes out or I can clear code with my scanner. A day or two can go by and code comes back. Seems to happen most frequently wirh cruise control on and going over an over pass and when I start down the other side CEL lights back up. Car runs fine. O2 senssor has been replaced (Bosch). No apparent vacuum leaks. MAF has been cleaned. Any suggestions?
 
I had the code 2 weeks ago and threw in a different O2 I had lying around. Problem solved. Maybe the rear bank of the LIM is not opening under throttle causing that bank of cylinders not to have the proper air.
 
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