Code 4400: Lambda-Control, Upper control limit reached

Patient is a 2004 K1200GT and has been running fine. While working on another bike I discovered an incompatibility between my new GS-911 WiFi unit and my iPad Air2 when connecting over wifi--the GS-911 cannot see version MA2.4 Motronics when configured that way. Opened a ticket with Hexcode, they are aware of the problem and looking to fix in the next software or firmware release. So, per their instructions I connected via laptop and USB cable on my own bike, just to verify that PC/USB would work.

An autoscan reported the error shown in the title. I have not noticed fuel mileage issues nor any running issues, but clearly the code indicates a problem somewhere. I cleared all the codes, connected the GS-911, started the bike cold, and allowed it to idle until up to temp. So, I've collected a CSV file of relevant data and am trying to narrow down the possible problems. My three main suspects are fuel pressure, fuel volume (obstructed fuel filter?) or a bad O2 sensor. The bike is due for a new fuel filter so I will make that change, along with installing the BeemerBoneyard replacement for the curved hose. I do not have a fuel pressure gauge but could probably borrow one if need be. That leads to the questions on the O2 sensor:

1. What is considered a normal lambda value at cold startup? And at normal operating temp?

2. As the bike was coming into temp I noticed some wild fluctuation in the lambda readings. Is this normal, or should the value move progressively and be relatively stable? BTW, this was a straight idle, no throttle blipping until near the end just before shutdown.

3. If I need to replace the O2 sensor does anyone have the correct Bosch cross-reference number? I'm betting it's a part I can get at a FLAPS at a significant savings if I can get the Bosch number.

I have cleared all codes on the bike and will be taking it out tomorrow morning for a 100mi run so I can read codes again to see if the code is recurring.

Thanks for the help,

DeVern

I "think" I recall a section in the Oilheads threads where Roger talks about the O2 sensor (I'm too lazy to look it up), saying that it does fluctuate until the final temperature is reached - when cold, it sends out a voltage back to the computer, the computer makes an adjustment which modifies the fuel mix, then reads the sensor again; this is reiterative until stability is reached.

I seem to recall a couple of YouTube videos that also show that action on a scope - the voltage is similar to a square wave whose "swing" decreases until the operating temp is reached.

As for the upper control limit - either a bad sensor, or something else is keeping the mix from reaching the computer's idea of optimal.

DeVern,

For as on top of most things that you are on these bikes, I am amazed that you don't have a fuel pressure gauge. Try Harbor Freight for a very serviceable fuel pressure gauge set.

As you know, the code you are getting suggests that the mixture is up against the limit of what the O2 sensor circuit can compensate for. Since I don't have O2 sensor era bikes, I don't remember whether "upper limit" is too rich or too lean (I'm guessing too rich, but that is just a guess). Regardless, Possibilities are: fuel pressure too high or too low (regulator), regulator return hose kinked, fuel filter plugged, vacuum leak (air leak AFTER the air flow meter; crankcase vent hose, throttle body manifolds upper or lower etc.), bad air filter to plenum hose, bad temp sensor, bad O2 sensor, maybe even a bad EFI computer.


I'm sure you'll find it and report back to us to expand the community knowledge.

98lee said:

DeVern,

For as on top of most things that you are on these bikes, I am amazed that you don't have a fuel pressure gauge. Try Harbor Freight for a very serviceable fuel pressure gauge set.

As you know, the code you are getting suggests that the mixture is up against the limit of what the O2 sensor circuit can compensate for. Since I don't have O2 sensor era bikes, I don't remember whether "upper limit" is too rich or too lean (I'm guessing too rich, but that is just a guess). Regardless, Possibilities are: fuel pressure too high or too low (regulator), regulator return hose kinked, fuel filter plugged, vacuum leak (air leak AFTER the air flow meter; crankcase vent hose, throttle body manifolds upper or lower etc.), bad air filter to plenum hose, bad temp sensor, bad O2 sensor, maybe even a bad EFI computer.

I'm sure you'll find it and report back to us to expand the community knowledge.

Click to expand...

LOL! I’ve not previously had a need to check fuel pressure on either of the two brick-k bikes I’ve had. But you’re right-a couple feet of hose, a tee, the cheap HF gauge, and the plastic QDs I swapped out of this bike and I can quickly be ready to test fuel pressure. But at 100k miles I’m more suspicious of the O2 sensor, and I see that EME has a direct plug-in replacement at a reasonable price.

After clearing all the codes I took the rig for a 100mi run this morning, a breakfast run with my wife in the sidecar. Why drain the tank for filter service when you can ride the fuel off? I’ll start with a new FF tomorrow, but a check for faults after this morning’s run produced no fault codes. I hate transient issues...

Best,
DeVern