Hi everyone, really would like some help. I'll start at the beginning... I have a 2016 scrambler with Termi race slip-on with Up Map key installed, no baffles.. engine light had never been on in 1500 miles. I didn't like the surging at low rpm/speed so I installed a pair of o2 sensor eliminators (eBay ones from Greece... they are resistors that give a constant value reading to the ecu instead of varying voltages), physically removed the o2 sensors and used plugs to cap the holes in the exhaust pipes. Took it for a ride, surging had gone BUT when accelerating hard ie. throttle opened up lots, if I then fully closed the throttle for 2 or 3 seconds, the engine management light would come on. It would stay on for around 2 seconds. I presumed that even though the o2 sensor eliminators gave a constant voltage value for the ecu, the ecu wasn't entirely happy and so produced the engine management light. At this point I must point out I still had the oem air filter in. I felt that I wanted the fuelling to be spot on so I had my ecu flashed by Rexxer. I told them I had the Termi race slip-on, up map key installed, no baffles, o2 sensors disconnected and physically removed and that I wanted the o2 sensors switched off in the ecu. I also installed an pipercross air filter. At this point I also removed the o2 sensor eliminators. Put the newly flashed ecu back into the bike, started it up, let it idle for 5 min (didn't touch the throttle) and then rode it gently for 10 miles after which I rode it harder for another 10 miles. When giving lots of throttle and then closing the throttle fully shut (same way as before), yet again the engine management light comes on in the exact same way as before! I know I need to get it on a diagnostic machine to see what is going on and for it to hopefully tell me an error code. It's been suggested that a sensor is playing up and originally with the o2 sensors connected and in use, it was masking the fault. Has anyone experienced anything similar or have any ideas? Many thanks.
If you were going to start at the beginning you'd have introduced yourself properly in the newbies section
Hi Duncan, I have the same bike with the Termi slip-on, the up-map and no baffles. Surging has never been an issue with my bike and I have left it well alone. If it ain't broke don't fix it. Often the trouble with trying to fix one little niggling fault is that the "fix" introduces other faults. The Rexxer remap should have removed the requirement for the O2 sensors. Assuming that the fault is a sensor issue, what does that leave? Crank/rpm sensor : These tend to either fail completely or fail when they are hot and can cause misfires at higher revs or just a non-runner and often don't bring on the MIL (Malfunction Indicator Lamp). Engine temperature sensor: The ECU uses its output to adjust the mixture to suit engine temperature. ie. Rich for a cold engine, leaning out as it warms up. Not a likely candidate for the MIL on at closed throttle as it's output will not be affected by throttle openings. Air temperature sensor: Same as above Throttle Position Sensor (TPS) : Tells the ECU how far the throttle is open. If there is a noisy section of the track at the closed throttle end that could certainly put the MIL on but it would do that regardless of any of the changes you have made. Manifold Absolute Pressure (MAP) sensor : This tells the ECU the air pressure inside the throttle body. Depending on how the ECU uses this signal it may only be used to adjust the fueling according to the air pressure or it can be used along with the TPS value so that the ECU can measure the weight of air entering the engine and adjust the fuel to match it. I'm not sure that the Scrambler ECU is that clever though. If the MAP sensor output is out of range then that also could activate the MIL. It's difficult to say whether the fault was masked or has occurred as a result of the changes or if it is a new fault which has occurred simultaneously and it's going to be difficult for you to put it back to standard to find out if it goes away. The MC3 software from JPdiag should, with the right hardware, be able to communicate with the Scrambler ECU to read any stored DTCs (Diagnostic Trouble Codes). Incidentally, low rpm surging is usually caused by a too lean condition. Did anyone look at adjusting the throttle body air bypass?
Hi Derek, Thank you for the great reply. I made a mistake earlier in the process of fault finding. When I installed the o2 sensor eliminators aka resistors, when it threw the engine light on, whilst still having the original ecu map on, I should of re-installed the o2 sensors and electrically connected them back up. If the engine light then didn't come on I would of definitely known that it was directly related to the o2 sensors being removed and disconnected. I could of then physically left the sensors in place but re-introduced the resistors. If the problem didn't occur then it would be a physical problem ie o2 sensor blanking plugs not sealing correctly. I might re-install the o2 sensors but not electrically connect them and see what happens. After which depending on the findings, I can electrically connect them to see if that has any effect. (As a side note, I'm pretty confident the o2 sensors have been disabled in the ecu by rexxer otherwise I would have a engine light on all the time).
Derrick Thanks for your easy to understand explanation of how the sensors work with the e.c.u. This is information I have been interested in but didn't know.
I decided to install the o2 sensors back into my bike and connect them back up. Took it on a test ride and the engine light stayed OFF! I pulled over, quickly disconnected the o2 sensors and did the same route, the engine light came ON. So my theories are: 1) RexXer haven't properly turned the o2 sensors off in the ecu. 2) RexXer have disabled the o2 sensor in the ecu but for some reason the ecu is still receiving a signal from the o2 sensors.
