Another P1173 thread

[jkempf]

02 Disco 2 bone stock 160k miles in Central Vermont.

Read all the P1173 threads, and I am going to put a new O2 sensor in Bank 2, sensor 2 this week just because I have one on the shelf.

But here is the weird part and I am wondering what it points to:?

I just did an upper manifold off procedure to put in new coil packs, new wires, plugs are recent, did the crankcase breathers as they were rotten, replaced the flame arrestor and cleaned everything, put on a new TB heater cover and all rubber lines were replaced, and did the valve cover gaskets while I was in there as it is sort of all one job. Had a very intermittent P1173 before this and verified that I had a plugged breather system during this work. All went well and my humid rough running starts are all cured now.

The P1173 came back and here's how. I drive about a train commute trip twice a week which is about 50 miles one way. Normally I tank up near the train station because the gas is like $0.30 cheaper there. So I normally run the tank low at that end of the trip on Sunday. What I am now noticing is that the P1173 code comes on about 10 minutes after filling the tank almost every week. I clear it and it comes back again after filling the tank a week later under the same circumstances. The tank cap is perfect and sealing. I have gotten that evap code before. I get only P1173 and only in this way. I am now starting to suspect that there is still some vacuum or emissions related thing driving this code but cannot for the life of me come up with a scenario that would create this symptom.

Any ideas? No matter how wacko?

 

[jkempf]

A week later and it did the same thing. One whole tank of gas and I filled it up today and it spit out P1173 ten minutes after fill up. Weird. Tank ventilation system?

 

[jkempf]

One week later: Seems it is two starts after the fill up plus a bit of run time and P1173. That has to be some sort of other system bleeding something, either gas fumes or air, into the right bank causing some sort of mixture signal out of bounds.

If I clear the code it doesn't come back until the next fill and run cycle. As long as you don't open the tank there is no code. Open the tank when very low and refill and then cap the tank and drive it comes back.

Stumped!

O2 Disco 2 stock

 

[seventyfive]

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DTC P1173
Lambda sensor aging tv bank 2 Drive cycle C:Signal out of range - above maximum.

DTC P1173
Lambda sensor aging tv bank 2 Drive cycle C:Signal out of range - below minimum.


Possible causes by suggested order of priority:
^ Deteriorated upstream oxygen sensor.
^ Deteriorated downstream oxygen sensor.

Deteriorated Upstream Oxygen Sensor.
POSSIBLE FAULTS
^ The Motronic ECM has internally diagnosed that the switching characteristics of this oxygen sensor have degraded to a point where exhaust emissions will be increased.
^ This fault is normally caused by the aging of the sensor in normal operation, however, this effect can be accelerated if the sensor has been contaminated with oil or other surface contamination.

Deteriorated Downstream Oxygen Sensor
POSSIBLE FAULTS
^ The Motronic ECM has internally diagnosed that the characteristics of the upstream oxygen sensor have degraded to a point where exhaust emissions will be increased, however, this fault can sometimes be caused by the failure of the downstream sensor on the same bank causing an incorrect fault diagnosis. Also if both oxygen sensors (upstream and downstream) are flagged as faulty then the fault may in fact be only in the downstream sensor.
^ The fault is normally caused by the aging of the sensor(s) in normal operation, however, the effect can be accelerated if the sensor has been contaminated with oil or other surface contamination.
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[jkempf]

Why only after I fill the tank? That's the part that makes no sense. Vehicle is running perfect and has been getting better than ever mileage. I have a downstream to put in so I will do that. have to get an upstream if that doesn't work. Don't see how filling the tank triggers the Check engine light. Good confirmation that it is two driving cycles after the code is stored so that means that filling the tank starts the process.

 

[jkempf]

OK, rereading this maybe what is happening is that I am driving this thing around town all week and on the weekend I drive it past 50MPH for an hour to go to the train station. That would get it up in high gear with enough time to trip this particular code. At least that is something to go test and solve.

THANKS!