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Got a few codes on the way home!!

N

Newsvt

Veteran CEG'er
Joined
Apr 30, 2008
Messages
654
Location
Milwaukee, WI
So i picked up the car last night and it ran perfect for the 740miles i drove it home, i got a CEL light last night so i checked it today.. I got 3 codes, PO171, PO174, and PO1131? I know the first to are bank 1 and 2 running lean but whats 1131 mean? Can someone help me fix this!! thanks!!

p.s The cars a 1998 svt tour, with an 02' 3L escape motor, with svt upper and lower! The car does have a custom chip with tune.
 
I cleared the codes today to see if they would stay off, they came on after maybe an hour. The car does run and drive fine, but when I let it sit and idle it will idle low at maybe 500 and sometimes its a little lower. Any help would be appreciated, I have searched both the old and new forums with code po1131.
 
OBD-II CEL codes


P1131 -[FONT=arial,verdana,helvetica,sans-serif][SIZE=-0][FONT=arial,verdana,helvetica,sans-serif]Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1.


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I searched three the engine bay and can't really seem to fine anything, I'm gonna have a buddy look at it maybe im over looking something, thanks for the links, that's a very good write up.

I'll keep everyone updated!
 
so I did find out that there are no precats, and the car has not been tuned since the headers were put on. I did do a search but couldn't find exacly what I was looking for. If I were to do a milelimintor would this clear up the idle, correct me if im wrong but the car is trying to account for the precats but there not there so its making it idle bad and throwing the codes above??
 
Well the code you're getting is for a bad upstream o2 sensor, so swap that first while keeping an eye out for vacuum leaks.
 
Dyoel182 said:
Well the code you're getting is for a bad upstream o2 sensor, so swap that first while keeping an eye out for vacuum leaks.
Click to expand...


So the codes im threwing wouldnt have anything to do with the precats missing? I thought i would be throwing bank 1 code cus of this, as the codes only came on after the headers were installed on the car, with no precats? Thats also when i the idle started acting up?
 
Actually, no. The sensor is not SWITCHING, meaning that it's not doing the switch above and below .5 volt. .2 is lean and .8 is rich, normal running has voltage constantly jumping back and forth across .5 volt. When something goes wrong like vacuum leak, voltage locks at .2 or so if there is not enough fuel adjustment to bring it back up. That's on a good working sensor. It's telling you the system cannot add enough fuel to correct the problem. A sensor can go bad for various reasons like breakage, but the usual old age problem is that the sensor which when new switches very rapidly begins to slow down that switching a whole lot.
 
amc49 said:
Actually, no. The sensor is not SWITCHING, meaning that it's not doing the switch above and below .5 volt. .2 is lean and .8 is rich, normal running has voltage constantly jumping back and forth across .5 volt. When something goes wrong like vacuum leak, voltage locks at .2 or so if there is not enough fuel adjustment to bring it back up. That's on a good working sensor. It's telling you the system cannot add enough fuel to correct the problem. A sensor can go bad for various reasons like breakage, but the usual old age problem is that the sensor which when new switches very rapidly begins to slow down that switching a whole lot.
Click to expand...


So should I start by doing the o2 and well I'm in there spray around and look for any vaccum leaks?
 
The heating element only heats the sensor, sensor will not read properly until good and hot, heater is to allow sensor to achieve temp quicker so PCM can go to closed loop quicker and thus tighten up emissions. Earliest sensors had no heater at all. The sensor itself once hot generates a voltage that varies according to amount of oxygen remaining in exhaust. That voltage varies from around .1 to .9 volts. The middle of the range, or .5 is the number interpreted by the PCM as 14.7/1 air/fuel ratio or perfect mix. The PCM can't hit "perfect" all the time so it averages that out by constantly over richening and over leaning the mixture by longer and shorter injector on times. If you hook up a device to oxy sensor that can read out the voltages on a normally running car, you can see that switching as the voltages jump all over the place both above and below that .5 volt threshold. That is on a so-called "narrow" band sensor, the ones now can control even closer as they can control all over the fuel/air map, not locked into that narrow voltage. The narrow switching point is great for economy/emissions but not for full power as in high performance because the numbers for hi perf are more in the region of 12-13/1. The new wide band sensors can do that much easier.
 
In answer to the question, sensor has no output voltage until it hits a certain temperature. Older models had no heater, sensor heated up by just laying in exhaust gas stream. Car builders realized PCM took too long to go to closed loop, can't close loop until sensor is hot, alive and "switching", so they added the heater to speed up the wait. Most emissions now from a car come before car is warmed up, faster that happens the less total emissions car puts off. That's got a lot to do with what seems like a lot more water and radiator hoses too than used to be on older cars. Whole idea is to get the motor to temp quicker. Ever seen a Contour Zetec 4 lower radiator hose? That's a scary looking thing!!
 
Well I did find a vaccum leak today, its coming from the lim gasket, so as long as im in the we'll do the uim gasket as well as a good cleaning!
 
Well I sprayed carb cleaner and as soon as it hit the lim the idle jumped, and you can her a vaccum leak and that's where it seems to be coming from. We'll get more into it on Monday and see if I can find anything else.

I walked out today to find I leaked a good amount of coolant, and now the light is on! I seen it driping, it was somewhere above the oil filter, all I can think of is the svt oil cooler. I did get under the car and it wasn't leaking and I couldn't see anything wet.ill look Monday and get back to everyone, I haven't checked anything cus I had to go to work and didnt have time, I can in the morning!
 
I found my leak today and took care of that. The small return line that comes off the resavior was stuck under my imrc cover and was rubbing on the belt by the water pump. I also took out the silencers out of the exaust the car sounds pretty good now, when I get my camra fixed I'll have to post a video up.
 
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