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At Sunday's tech session, Herman (scarver) put his computer on my LT and it showed a faulty O2 Sensor, Should I replace it with a generic Bosche one $79 from beemerboneyard or a Bosche one from Bob's BMW for $133? What do you guy's suggest? Noticed that my gas mileage was terrible so it is probably shot, 38K on the bike.

Thanks
Bo
 

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As long as it is a Bosche that is specified for the BMW K1200 LT, I would get the Boche... probably what your going to get if you order from BMW anyway. I doubt the BMW part number is going to make that much difference.

If I remember correctly, O'Riley Auto parts sells the Bosche for the K1200LT too... I am not sure if you have O'Riley's down in TX or not. If you do, you might give them a call.
 

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I got the one from beemerboneyard when mine went out. Been working great ever since. MPG is back to 45+ after it slipped to around 27 with the bad O2 sensor (in the middle of a BB1500 Iron Butt ride). Easy to install.
 

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How do you know it's the O2 sensor?

Just wondering what the symptoms of a failed sensor would be. I guess poor mileage for one, but are there others?

Tks in advance,

John
 

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O2 sensors are pretty much identical in their function... (ok, everyone jump in here and say how wrong I am..)

If the "Bosch" one you get at your local dis-kount partz place looks like the one you remove, including the wiring connector then I'd run it.

If the Mileage improves, EUREKA! you fixed it..

For folks like myself, here are some other more involved steps... from a CAR site... http://www.gnttype.org/techarea/ecmsensors/O2sensors.html

How does an O2 sensor work?


An Oxygen sensor is a chemical generator. It is constantly making a comparison between the Oxygen inside the exhaust manifold and air outside the engine. If this comparison shows little or no Oxygen in the exhaust manifold, a voltage is generated. The output of the sensor is usually between 0 and 1.1 volts. All spark combustion engines need the proper air fuel ratio to operate correctly. For gasoline this is 14.7 parts of air to one part of fuel. When the engine has more fuel than needed, all available Oxygen is consumed in the cylinder and gasses leaving through the exhaust contain almost no Oxygen. This sends out a voltage greater than 0.45 volts. If the engine is running lean, all fuel is burned, and the extra Oxygen leaves the cylinder and flows into the exhaust. In this case, the sensor voltage goes lower than 0.45 volts. Usually the output range seen seen is 0.2 to 0.7 volts.

The sensor does not begin to generate it's full output until it reaches about 600 degrees F. Prior to this time the sensor is not conductive. It is as if the circuit between the sensor and computer is not complete. The mid point is about 0.45 volts. This is neither rich nor lean. A fully warm O2 sensor *will not spend any time at 0.45 volts*. In many cars, the computer sends out a bias voltage of 0.45 through the O2 sensor wire. If the sensor is not warm, or if the circuit is not complete, the computer picks up a steady 0.45 volts. Since the computer knows this is an "illegal" value, it judges the sensor to not be ready. It remains in open loop operation, and uses all sensors except the O2 to determine fuel delivery. Any time an engine is operated in open loop, it runs somewhat rich and makes more exhaust emissions. This translates into lost power, poor fuel economy and air pollution.

The O2 sensor is constantly in a state of transition between high and low voltage. Manfucturers call this crossing of the 0.45 volt mark O2 cross counts. The higher the number of O2 cross counts, the better the sensor and other parts of the computer control system are working. It is important to remember that the O2 sensor is comparing the amount of Oxygen inside and outside the engine. If the outside of the sensor should become blocked, or coated with oil, sound insulation, undercoating or antifreeze, (among other things), this comparison is not possible.

How can I test my O2 sensor?


They can be tested both in the car and out. If you have a high impedance volt meter, the procedure is fairly simple. It will help you to have some background on the way the sensor does it's job. Read how does an O2 sensor work first.

Testing O2 sensors that are installed.


The engine must first be fully warm. If you have a defective thermostat, this test may not be possible due to a minimum temperature required for closed loop operation. Attach the positive lead of a high impedance DC voltmeter to the Oxygen sensor output wire. This wire should remain attached to the computer. You will have to back probe the connection or use a jumper wire to get access. The negative lead should be attached to a good clean ground on the engine block or accessory bracket. Cheap voltmeters will not give accurate results because they load down the circuit and absorb the voltage that they are attempting to measure. A acceptable value is 1,000,000 ohms/volt or more on the DC voltage. Most (if not all) digital voltmeters meet this need. Few (if any) non-powered analog (needle style) voltmeters do. Check the specs for your meter to find out. Set your meter to look for 1 volt DC. Many late model cars use a heated O2 sensor. These have either two or three wires instead of one. Heated sensors will have 12 volts on one lead, ground on the other, and the sensor signal on the third. If you have two or three wires, use a 15 or higher volt scale on the meter until you know which is the sensor output wire.

When you turn the key on, do not start the engine. You should see a change in voltage on the meter in most late model cars. If not, check your connections. Next, check your leads to make sure you won't wrap up any wires in the belts, etc. then start the engine. You should run the engine above 2000 rpm for two minutes to warm the O2 sensor and try to get into closed loop. Closed loop operation is indicated by the sensor showing several cross counts per second. It may help to rev the engine between idle and about 3000 rpm several times. The computer recognizes the sensor as hot and active once there are several cross counts.

You are looking for voltage to go above and below 0.45 volts. If you see less than 0.2 and more than 0.7 volts and the value changes rapidly, you are through, your sensor is good. If not, is it steady high (> 0.45) near 0.45 or steady low (< 0.45). If the voltage is near the middle, you may not be hot yet. Run the engine above 2000 rpm again. If the reading is steady low, add richness by partially closing the choke or adding some propane through the air intake. Be very careful if you work with any extra gasoline, you can easily be burned or have an explosion. If the voltage now rises above 0.7 to 0.9, and you can change it at will by changing the extra fuel, the O2 sensor is usually good.

If the voltage is steady high, create a vacuum leak. Try pulling the PCV valve out of it's hose and letting air enter. You can also use the power brake vacuum supply hose. If this drives the voltage to 0.2 to 0.3 or less and you can control it at will by opening and closing the vacuum leak, the sensor is usually good.

If you are not able to make a change either way, stop the engine, unhook the sensor wire from the computer harness, and reattach your voltmeter to the sensor output wire. Repeat the rich and lean steps. If you can't get the sensor voltage to change, and you have a good sensor and ground connection, try heating it once more. Repeat the rich and lean steps. If still no voltage or fixed voltage, you have a bad sensor.

If you are not getting a voltage and the car has been running rich lately, the sensor may be carbon fouled. It is sometimes possible to clean a sensor in the car. Do this by unplugging the sensor harness, warming up the engine, and creating a lean condition at about 2000 rpm for 1 or 2 minutes. Create a big enough vacuum leak so that the engine begins to slow down. The extra heat will clean it off if possible. If not, it was dead anyway, no loss. In either case, fix the cause of the rich mixture and retest. If you don't, the new sensor will fail.

Testing O2 sensors on the workbench.


Use a high impedance DC voltmeter as above. Clamp the sensor in a vice, or use a plier or vice-grip to hold it. Clamp your negative voltmeter lead to the case, and the positive to the output wire. Use a propane torch set to high and the inner blue flame tip to heat the fluted or perforated area of the sensor. You should see a DC voltage of at least 0.6 within 20 seconds. If not, most likely cause is open circuit internally or lead fouling. If OK so far, remove from flame. You should see a drop to under 0.1 volt within 4 seconds. If not likely silicone fouled. If still OK, heat for two full minutes and watch for drops in voltage. Sometimes, the internal connections will open up under heat. This is the same a loose wire and is a failure. If the sensor is OK at this point, and will switch from high to low quickly as you move the flame, the sensor is good. Bear in mind that good or bad is relative, with port fuel injection needing faster information than carbureted systems.

ANY O2 sensor that will generate 0.9 volts or more when heated, show 0.1 volts or less within one second of flame removal, AND pass the two minute heat test is good regardless of age. When replacing a sensor, don't miss the opportunity to use the test above on the replacement. This will calibrate your evaluation skills and save you money in the future. There is almost always *no* benefit in replacing an oxygen sensor that will pass the test in the first line of this paragraph.
 

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You know your on a BMW M/C forum when............

cfell said:
O2 sensors are pretty much identical in their function... (ok, everyone jump in here and say how wrong I am..)

If the "Bosch" one you get at your local dis-kount partz place looks like the one you remove, including the wiring connector then I'd run it.

If the Mileage improves, EUREKA! you fixed it..

For folks like myself, here are some other more involved steps... from a CAR site... http://www.gnttype.org/techarea/ecmsensors/O2sensors.html

How does an O2 sensor work?



An Oxygen sensor is a chemical generator. It is constantly making a comparison between the Oxygen inside the exhaust manifold and air outside the engine. If this comparison shows little or no Oxygen in the exhaust manifold, a voltage is generated. The output of the sensor is usually between 0 and 1.1 volts. All spark combustion engines need the proper air fuel ratio to operate correctly. For gasoline this is 14.7 parts of air to one part of fuel. When the engine has more fuel than needed, all available Oxygen is consumed in the cylinder and gasses leaving through the exhaust contain almost no Oxygen. This sends out a voltage greater than 0.45 volts. If the engine is running lean, all fuel is burned, and the extra Oxygen leaves the cylinder and flows into the exhaust. In this case, the sensor voltage goes lower than 0.45 volts. Usually the output range seen seen is 0.2 to 0.7 volts.

The sensor does not begin to generate it's full output until it reaches about 600 degrees F. Prior to this time the sensor is not conductive. It is as if the circuit between the sensor and computer is not complete. The mid point is about 0.45 volts. This is neither rich nor lean. A fully warm O2 sensor *will not spend any time at 0.45 volts*. In many cars, the computer sends out a bias voltage of 0.45 through the O2 sensor wire. If the sensor is not warm, or if the circuit is not complete, the computer picks up a steady 0.45 volts. Since the computer knows this is an "illegal" value, it judges the sensor to not be ready. It remains in open loop operation, and uses all sensors except the O2 to determine fuel delivery. Any time an engine is operated in open loop, it runs somewhat rich and makes more exhaust emissions. This translates into lost power, poor fuel economy and air pollution.

The O2 sensor is constantly in a state of transition between high and low voltage. Manfucturers call this crossing of the 0.45 volt mark O2 cross counts. The higher the number of O2 cross counts, the better the sensor and other parts of the computer control system are working. It is important to remember that the O2 sensor is comparing the amount of Oxygen inside and outside the engine. If the outside of the sensor should become blocked, or coated with oil, sound insulation, undercoating or antifreeze, (among other things), this comparison is not possible.

How can I test my O2 sensor?


They can be tested both in the car and out. If you have a high impedance volt meter, the procedure is fairly simple. It will help you to have some background on the way the sensor does it's job. Read how does an O2 sensor work first.

Testing O2 sensors that are installed.


The engine must first be fully warm. If you have a defective thermostat, this test may not be possible due to a minimum temperature required for closed loop operation. Attach the positive lead of a high impedance DC voltmeter to the Oxygen sensor output wire. This wire should remain attached to the computer. You will have to back probe the connection or use a jumper wire to get access. The negative lead should be attached to a good clean ground on the engine block or accessory bracket. Cheap voltmeters will not give accurate results because they load down the circuit and absorb the voltage that they are attempting to measure. A acceptable value is 1,000,000 ohms/volt or more on the DC voltage. Most (if not all) digital voltmeters meet this need. Few (if any) non-powered analog (needle style) voltmeters do. Check the specs for your meter to find out. Set your meter to look for 1 volt DC. Many late model cars use a heated O2 sensor. These have either two or three wires instead of one. Heated sensors will have 12 volts on one lead, ground on the other, and the sensor signal on the third. If you have two or three wires, use a 15 or higher volt scale on the meter until you know which is the sensor output wire.

When you turn the key on, do not start the engine. You should see a change in voltage on the meter in most late model cars. If not, check your connections. Next, check your leads to make sure you won't wrap up any wires in the belts, etc. then start the engine. You should run the engine above 2000 rpm for two minutes to warm the O2 sensor and try to get into closed loop. Closed loop operation is indicated by the sensor showing several cross counts per second. It may help to rev the engine between idle and about 3000 rpm several times. The computer recognizes the sensor as hot and active once there are several cross counts.

You are looking for voltage to go above and below 0.45 volts. If you see less than 0.2 and more than 0.7 volts and the value changes rapidly, you are through, your sensor is good. If not, is it steady high (> 0.45) near 0.45 or steady low (< 0.45). If the voltage is near the middle, you may not be hot yet. Run the engine above 2000 rpm again. If the reading is steady low, add richness by partially closing the choke or adding some propane through the air intake. Be very careful if you work with any extra gasoline, you can easily be burned or have an explosion. If the voltage now rises above 0.7 to 0.9, and you can change it at will by changing the extra fuel, the O2 sensor is usually good.

If the voltage is steady high, create a vacuum leak. Try pulling the PCV valve out of it's hose and letting air enter. You can also use the power brake vacuum supply hose. If this drives the voltage to 0.2 to 0.3 or less and you can control it at will by opening and closing the vacuum leak, the sensor is usually good.

If you are not able to make a change either way, stop the engine, unhook the sensor wire from the computer harness, and reattach your voltmeter to the sensor output wire. Repeat the rich and lean steps. If you can't get the sensor voltage to change, and you have a good sensor and ground connection, try heating it once more. Repeat the rich and lean steps. If still no voltage or fixed voltage, you have a bad sensor.

If you are not getting a voltage and the car has been running rich lately, the sensor may be carbon fouled. It is sometimes possible to clean a sensor in the car. Do this by unplugging the sensor harness, warming up the engine, and creating a lean condition at about 2000 rpm for 1 or 2 minutes. Create a big enough vacuum leak so that the engine begins to slow down. The extra heat will clean it off if possible. If not, it was dead anyway, no loss. In either case, fix the cause of the rich mixture and retest. If you don't, the new sensor will fail.

Testing O2 sensors on the workbench.


Use a high impedance DC voltmeter as above. Clamp the sensor in a vice, or use a plier or vice-grip to hold it. Clamp your negative voltmeter lead to the case, and the positive to the output wire. Use a propane torch set to high and the inner blue flame tip to heat the fluted or perforated area of the sensor. You should see a DC voltage of at least 0.6 within 20 seconds. If not, most likely cause is open circuit internally or lead fouling. If OK so far, remove from flame. You should see a drop to under 0.1 volt within 4 seconds. If not likely silicone fouled. If still OK, heat for two full minutes and watch for drops in voltage. Sometimes, the internal connections will open up under heat. This is the same a loose wire and is a failure. If the sensor is OK at this point, and will switch from high to low quickly as you move the flame, the sensor is good. Bear in mind that good or bad is relative, with port fuel injection needing faster information than carbureted systems.

ANY O2 sensor that will generate 0.9 volts or more when heated, show 0.1 volts or less within one second of flame removal, AND pass the two minute heat test is good regardless of age. When replacing a sensor, don't miss the opportunity to use the test above on the replacement. This will calibrate your evaluation skills and save you money in the future. There is almost always *no* benefit in replacing an oxygen sensor that will pass the test in the first line of this paragraph.
Mannnnn..............you just can't get this kinda stuff on the "OTHER" motorcycle forums!!! :rotf:
 

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Discussion Starter #7
Herman connected his GS911 to my bike and it reported that the Oxygen Sensor voltage did not change 300+ times, and my mileage has dropped significantly so that is why I think that I should replace it. I will check the cable first to make sure that it is pluged in. We have used the GS911 on 8 to 10 other LT's and it has not reported this fault on any others.

Has anyone bought a O2 (Lambda) Sensor from O'Riely Autoparts? Do I just take the one off and take it in and get one that looks the same? Any advice from someone that has done it would be great.

Thanks
 

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Interesting stuff, but I was in over my head after How does an O2 sensor work? :D

Good thing I have friends who understand this stuff. . .
 

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Tony.. O2, it's like a switch or a potentiometer.... when it gets hot from the exhaust gasses it generates a very low voltage that is "read/sensed/interpreted/crystal balled" by the black box.. to add or take away fuel in mixture.

The rest of the stuff is just to mess with ya.
 

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cfell said:
O2 sensors are pretty much identical in their function... (ok, everyone jump in here and say how wrong I am..)
You are 100% correct, all NARROW band O2 sensors operate the same way (some do it better than others), I won't get into wide band O2's.
Now for the bad news....On most car forums everyone agrees that Bosch O2 sensors are no good, sad but true. They tend to go bad earlier than they should and still more are bad right out of the box.
Solution? Get another brand. Most single wire (narrow band) O2's use the same style single pin connector (some use a heated 3 wire sensor). If the LT uses a different style connector than the others, you can simply cut the connector off of the bad sensor and cut the connector off the new one and using silver bering solider, solider the old connector to the new sensor. Be sure to use heat shrink (marine grade if you can) on all of the solider joints.
 

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Discussion Starter #11
Morley said:
You are 100% correct, all NARROW band O2 sensors operate the same way (some do it better than others), I won't get into wide band O2's.
Now for the bad news....On most car forums everyone agrees that Bosch O2 sensors are no good, sad but true. They tend to go bad earlier than they should and still more are bad right out of the box.
Solution? Get another brand. Most single wire (narrow band) O2's use the same style single pin connector (some use a heated 3 wire sensor). If the LT uses a different style connector than the others, you can simply cut the connector off of the bad sensor and cut the connector off the new one and using silver bering solider, solider the old connector to the new sensor. Be sure to use heat shrink (marine grade if you can) on all of the solider joints.
The LT has 4 wires. I guess 2 for the sensor and 2 for the heater?
 

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Discussion Starter #12
New O2 Sensor GOOD, old one BAD

Well, all is well. Thanks for the suggestion of O'Rielly Auto Parts. They had the O2 Sensor in stock, it turns out that it is the same one for the BMW Z3 and several other BMW Cars (who new they made cars?). I replaced it and then asked Herman (scarver) to test it again with his GS-911, and voila no faults. I haven't ridden it enough to know if my gas mileage is improved but my seat-of-the-pants feeling is that the O2 sensor is pretty important to both performance and fuel economy.

To replace it you only have to take the tupperware off of the left side and the shifter. You don't have to remove the gas tank. It is actually easier to change than the spark-plugs.
 

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Texas42 said:
Herman connected his GS911 to my bike and it reported that the Oxygen Sensor voltage did not change 300+ times,
So, is this a fair predictor of an imminent failure? The reason I ask is that I had an O2 sensor fail on my K1100LT on the '99 Iron Butt. It resulted in poor mileage and, eventually, a fouled spark plug. I was able to buy and change the plug, wich allowed the bike to run OK, but my mileage still sucked. When I finished, (very well, I might add :)), I had my dealer replace the O2 sensor. The bike had about 90,000 miles on it at the time.

OK, so in 13 days I leave for St. Louis and the '07 Iron Butt to make one more attempt at wining the damn thing for a second time, (which hasn't been done since the first two in '84 & '85). My '01 LT will have 160,000 on it when I arrive in St. Louis, (though, due to a screw up on my part, then engine, trans, clutch, etc. will only have about 55,000). I think, just for the peace of mind, I should change my O2 sensor.

What you you guys think?

TIA,

George
 

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Discussion Starter #15
grifscoots said:
It helps to unplug it:rotf:
and to un-screw it :( of course
 

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Texas42 said:
I don't know if the GS-911 will work on an K1100, I don't know if it has a diagnostic port.
I guess I wasn't clear; I'm on a K1200LT now. I was just explaining what happened on my K1100 when the O2 sensor failed.

GB
 

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Discussion Starter #18
yes, the GS-911 can diagnose lots of different things both about the motor, fuel injection and the ABS system on the LT. 199 for the USB only and 249 for the bluetooth/usb version.
 

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Finaly did mine

Well
I was working about 130 miles form home last week and my gas millage was only at 32.7 to 34.3 for the trips all 5 days (reset each day).
Mostly turnpike riding at 70 to 75mph (115 Miles) anywhere from 65 to 94 degrees.

lots of black soot on the chrome around the tailpipe.(running rich ?)
Did not do any diags on the O2 Sensor when I removed it, may do in a day or two will post results.

Went to Autozone yesterday and bought a Bosch 15738 (4 wire, Universal O2 sensor)
Universal = A supposed weather proof wire connector (you cut the original harness 4 inches from the sensor and splice in the new so it is the same length).

Went for a test ride after installing new O2 sensor and saddlebag lights from Ridewest (nice look easy to install)

only did about 75 miles as it was raining today but I am back up to 48.5 at 70 MPH on the freeway.
 

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That's interesting, I've had low gas mileage for the 2 years I've owned,(average 36). I attributed the low MPG due to the fact that most of my riding is backroads and generally twist the throttle too much, but sounds like I should check the O2. My buddy had a BMW 320 car for quite a few years, he was replacing O2's on the average of once a year. It must not have been that unusual, as there was an 02 sensor idiot light that would proudly glow yellow when said part failed.
 
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