Oxygen Sensor Fault Code

[Yeeha! Stephen]

GS-911 says #304 Oxygen Sensor Circuit Malfunction... Short Circuit to Earth.

 

Does that mean my Oxygen Sensor itself is bad and time to order?

 

Or do I look for a real short somewhere?

 

TIA

[T__]

 

Does that mean my Oxygen Sensor itself is bad and time to order?

 

Or do I look for a real short somewhere?

 

TIA

 

Stephen, if you believe the GS-911 is telling you the truth & a #304 is in fact an O2 short to ground on your Motronic system (you didn’t give us a bike make model or year) then yes that means your O2 (or O2 system wiring) is bad..

 

On the other hand if you are getting a false trouble code,, or the failure is pertaining to a different model or Motronic system,, or for some other reason the failure code isn’t true then who knows if you have an actual O2 failure..

 

Will the GS-911 allow you to monitor the O2 cross counts or voltage swings above & below .500 volts while riding? If so what action is the O2 showing?

 

Even if the GS-911 is showing a true O2 failure (output short to ground) there is no way of knowing if the problem is in the O2 itself or in the wiring (or connector pin out) without checking the wiring for possible grounding or connectors for being pinned incorrectly.. All the GS-911 is showing you is what the fueling computer sees not the actual O2 output..

 

Personally,, I would start the O2 system integrity check by accessing the black O2 output wire (don’t disconnect just add an access point) then hooking up a “high impedance” voltmeter between the O2 black wire & good chassis ground.. On a good warm (10 minutes of running or more) system you should see continuous varying O2 voltage with the voltage swinging from below .500 volts to above .500 volts (cross counts).. Maybe a steady voltage on a cold engine & under long term acceleration but should be always varying through .500v on normal warm engine steady throttle riding..

 

The other thing you could do is install a new O2 then see if that changes the GS-911 readings (expensive way to troubleshoot)..

 

A quick thought—Do you have an aftermarket fuel controller (like a Techlusion) on that bike? If so that could easily give you a strange O2 reading on the GS-911 as some of those fuel controllers spoof the O2 signal..

 

Hopefully someone from the board here can follow up with you on this as I am back on the road again in a short time (no computer access) so probably won’t check back in here (this web site) for quite a while..

 

Twisty

 

[Yeeha! Stephen]

I believe the GS911, it hasn't lied to me yet. I just didn't know what it was telling me. It wouldn't hurt to go ahead and put a new O2 sensor on, the old one was faithful to me The bike is an 1150 RT, stock bike - no gizmo's. Lotsa miles - 122k+ with original O2 sensor.

 

I was doing a throttle sync and started with a good idle balance... and then instantly it went wildly unbalanced. Like you had both Brass screws at opposite ajustments.

 

Thought it was clogged LBS's and then thought Air Leak. Checked both and they are fine.

 

Restarted the bike, got a good balance and them boom... imbalance again.

 

Went back and forth several times and then decided to look for fault codes on the GS 911. Found the above code. Code is not present when the bike is keyed off and keyed on. Restarts without the code ("Code Not Present" on the GS911) and shortly after the code pops up and the bike starts running badly. Idles very high, 1500 or greater, and shakes somewhat.

 

That help?

[smiller]

First I'd verify that it really is the O2 sensor that's causing your problem. Have you tried disconnecting the O2 sensor and seeing what happens? With the sensor disconnected the ECU should run in a 'limp in' open-loop mode that should provide reasonable performance and a proper idle. If the bike runs more-or-less OK without the O2 sensor and then goes nuts when it is connected then something is wrong with the sensor or its associated wiring, but if disconnecting the sensor doesn't make any difference then there's probably something else causing your problem.

[philbytx]

Just went through the same thing with my BMW car and I R&R'd the 02 sensor. Car runs great now...

 

Dollars to donuts its the o2 sensor and, as Seth said, if you unplug it when the bike is hot and running badly, restart and then the bike runs smoother, its definitely the 02 sensor.

 

One reason it can start running ok when you first start up cold/warm then goes off tune is that our 02 sensors are heated and only start working when off idle and it has reached temps around 600F.

 

 

 

[T__]

I believe the GS911, it hasn't lied to me yet. I just didn't know what it was telling me. It wouldn't hurt to go ahead and put a new O2 sensor on, the old one was faithful to me The bike is an 1150 RT, stock bike - no gizmo's. Lotsa miles - 122k+ with original O2 sensor.

 

I was doing a throttle sync and started with a good idle balance... and then instantly it went wildly unbalanced. Like you had both Brass screws at opposite ajustments.

 

Thought it was clogged LBS's and then thought Air Leak. Checked both and they are fine.

 

Restarted the bike, got a good balance and them boom... imbalance again.

 

Went back and forth several times and then decided to look for fault codes on the GS 911. Found the above code. Code is not present when the bike is keyed off and keyed on. Restarts without the code ("Code Not Present" on the GS911) and shortly after the code pops up and the bike starts running badly. Idles very high, 1500 or greater, and shakes somewhat.

 

That help?

 

 

Stephen, don’t know what you have there? In any case the O2 shouldn’t have any effect on the TBI balance (or at least not enough to measure with a mercury gauge).. The TBI balance is basically the measure of air flow across the throttle plate to TBI bore (pressure delta across the throttle plate).. You have that air flow based on the air pumping ability of the engine not fueling or spark related.. You could shut the fuel off & disconnect the coil & drive the engine with an electric motor & still get a decent TBI balance as long as the valves are sealing & working correctly & there isn’t any intake or exhaust restrictions..

 

You might have a couple of problems there-- the TBI balance variance is not O2 related,, that would be more likely a sticking valve or exhaust restriction,, or maybe even a worn TBI throttle shaft or loose throttle plate (something mechanical effecting the engine vacuum or side to side pumping ability)..

 

The idle speed variance or rough running could easily be O2 related or even Motronic mapping related due to a sensor input problem.. Maybe check the Motronic grounding as well as TPS grounding & O2 grounding (could be a common ground problem).. A ground problem on either the O2 or TPS can drive your fueling computer crazy.. On the same note it could be engine mechanical like a sticking valve or plugging cat converter..

 

As Seth mentioned definitely try running with the O2 disconnected as that might help point out the idle RPM problem.. It should have no effect on the TBI balance though (might slightly change the actual vacuum but not the side to side balance)..

 

CHECK YOUR HARNESS,, SENSOR,, & MOTRONIC GROUNDS for tightness & being clean & oxidation free..

 

Maybe also check your rocker arm end play,, if too tight a rocker could momentarily stick at low RPM’s as the engine heats & cause a rough idle along with a big cross side vacuum discrepancy..

 

Twisty

 

 

[Yeeha! Stephen]

Too hot in the garage this evening to mess with it. I'll try again in the morning and get back to ya!

 

Thanks...

[smiller]

Too hot in the garage this evening to mess with it.

Tell me about it. Man, it's getting old...

[Yeeha! Stephen]

Thanks for the help boys.

 

Still hot in the garage.

 

Checked the Roacker Arm end play. It's ok. The right Exhaust was a little tight, but not outside the limit of .05mm. It was at .06mm. I reset them all to .10mm, Max is .40.

 

Ran the bike from there... same prob.

 

Unplugged the sensor and it runs a little better. Got the carb stix to sort out fairly well. Runs really well off idle.

 

Plugged the sensor back in, and the balance held. It's too hot to mess with it now. I'm going to wait till the evening and go ride it, get it really warm, and check for faults again.

 

Secretly I'm hoping it was a dirty connection. Really I think I'll have to buy another one. Jeez, the dealer wants $225 for them.

 

Thinking of trying a sensor from Bosch for a BMW car. Autozone price $79.

 

 

Or one form these folks - almost half the dealer price @ $119 www.euromotoelectrics.com

 

 

Photo of mine is attached:

[Yeeha! Stephen]

OK boys,

Problem solved... sort off.

 

The reason for wildly different levels on my carb stix was the O2 Sensor. The GS 911 wasn't lying.

 

Bought one from these folks for 1/2 what the dealership wanted. http://www.euromotoelectrics.com/

 

I usually shop the Ft Worth dealership because with my 10% local club discount they will usually match/come close to Net prices. Not this time. I asked and they couldn't do it. Dealer price $225 plus 8.75% sales tax vs $119 + $5 shipping.

 

Installed the new sensor and got my stix to balance within 2 of the graduation marks which is 2 cmhg. The bad sensor wouldn't get closer than 40 cm.

 

Try as I might, I couldn't get the last little bit to balance. Messing with the cable pulley I found the T-Body wasn't on it's stop. With a small push with my finger it "popped" into place on the stop and the TB's went to perfect balance.

 

Turned the bike off and started looking for dirt on the pulley, or a sticking cable. Found that the throttle shaft wobbles a bit in it's "bushing". I guess there's a bushing in there that's worn out. The shaft moves enough to get stuck just a Hair off the throttle stop.

 

Now the next question... Is there a place to buy rebuild parts for these throttle bodies? Any home shop mech. out there building them in their garage for sale on the Net? I sure could use a set right now.

 

Bike runs ok for now. When it's really hot outside, and we're stopped at a light, the idle drops little by little until the bike dies. I can blip the throttle a couple of times and everything is fine. But you know how we hate to be one of "Those" riders! Ha!

 

Let me know if you hear anything. Plz and Thnks

 

 

[T__]

Stephen, o2 sensor CAN’T cause a TBI balance problem.. Can make the engine run bad but won’t effect intake manifold vacuum unless the engine is running SO bad it is farting & backfiring into the intake manifold..

 

You saying--“Messing with the cable pulley I found the T-Body wasn't on it's stop. With a small push with my finger it "popped" into place on the stop and the TB's went to perfect balance.”

 

Sounds more like your problem was with that TBI cam/cable area--- That WILL effect the TBI balance..

 

Twisty

 

[Yeeha! Stephen]

Strange but true. I don't know why it did it, but that's what happened.

 

When Seth suggested I unplug the O2 sensor, I did that and the balance came a lot closer. Plugged the bad sensor back in and the balance went wildly out of whack again. (really warm engine)

 

Got the new sensor in and immediately got a really good balance.

 

That's the only thing I messed with the whole week.

 

I'm using a Motion Pro mercury stick and when I say the balance was bad, I mean the right cyl was showing a little below normal and the left was way up toward the top of the stick.

 

Unplug the old sensor and the right came up some and the left came way down to within 3 of those marks which would be 6 cm hg.

 

Plug the new sensor in and without touching anything else, the mercury came to inside 2 cm hg on both cyl.

 

The right T-body pulley is just a hair off the stop. You can barely see it. But you can hear a faint click when it touches the stop when pushed by a finger.

 

When I close the TB to it's stop, they both come to as perfect a balance as I can get. Both on the same line of cm hg.

 

With the new O2 sensor, I have not been able to duplicate the severe imbalance I had with the bad sensor.

 

During the whole process, I've never touched the off-idle adjusment.

 

So, should I be looking for further trouble? I thought I was good to go.

 

Thinking of taking the TB's off and checking inside to see if there's a bent/broken/about to break butterfly inside.

 

Whacha' think along those lines?

[Boffin]

Bing offer Throttle body refurb kits, though if the bushing is too worn they may not help. There has however been a very good thread on ADVrider detailing a throttle body rebuild with this kit and instalation of a new bush.

 

Also mentioned are Motorworks' tickler killers which kill the ticking on RH throttle bodies. Unfortunately Motorworks will not sell to the USA or Canada anymore...

 

Andy