Discussion in 'Honda Acty References' started by Randy WCA, Jun 5, 2016.
Hi there, I was wondering if the Honda Acty will run if I eliminate the 02 sensor?
My check engine light was on and the tuck would run ok to it got warmed up then it would idle poorly and stumble when I accelerated. I changed the o2 sensor and the light went out and it runs great again.
The O2 Sensor is what tells the computer whether it is rich or lean so the computer can adjust the mixture for smooth running so it is recommended to run a O2 sensor for a decent running engine. If the computer is not receiving a signal from the O2 sensor it will default to the factory default parameters and will not run as good as it has self-learned to.
If the O2 sensor is disconnected, the engine control module will run in default factory mode and not run as good as it has self learned. Basically all engine controls are based on this principle, copied from a Bosch Motronic M1.3 for BMW and other makers at same period when our old Acty were produced:
Limited Operating Strategy (LOS)
In the event of a serious fault in one or more of the sensors or their wiring circuits, Motronic will substitute a fixed default value in place of the defective sensor. This procedure is often termed limp home. A serious fault occurs when the signal from the sensor is outside of its normal operating parameters. When operating in LOS the engine may actually run quite well with failure of one or more minor sensors. Since the substituted values are those of a hot engine, cold starting and running during the warm-up period may be less than satisfactory. Also, failure of a major sensor, ie the AFS, will tend to make driving conditions less easy. Once the fault has cleared, Motronic will once more accept the live signal from the sensor. The following LOS measures are taken in the event of a failure
AFS........................substitute values are calculated from the TS position. The load signal is fixed to 6.0 ms and the ignition timing to 20° BTDC once the TS contact is open.
ATS........................substitute value of 50° C . A code will not be set, and LOS will not commence until a minimum of 3 minutes after engine start and the engine idling for a minimum of 30 seconds.
CID sensor.............injectors are pulsed simultaneously
CO pot..................substitute value of 2.77 volts
CTS...................substitute value of 80° C if ATS value is greater than 20° C .
if ATS value is less than 20°C , substitute value of ATS value for first three minutes after engine start-up.
OS.....................substitute value, open loop control
TS.....................substitute values, restricted engine operation
AFS = air flow sensor
The AFS is located between the air filter and the throttle body. As air flows through the sensor it deflects a spring loaded vane (flap). The greater the volume of air, the more will the flap be deflected. The vane is connected to a wiper arm which wipes a potentiometer track and so varies the resistance of the track. This allows a variable voltage signal to be returned to the ECU. The voltage signal varies in proportion to the volume of air that flows through the vane.Three wires are used by the circuitry of this sensor and it is often referred to as a three wire sensor. A 5 volt reference voltage is applied to the resistance track with the other end connected to the AFS earth return circuit. The third wire is connected to the wiper arm. From the voltage returned, the ECU is able to calculate the volume of air (load) entering the engine and this is used to calculate the main fuel injection duration. To smooth out inlet pulses, a damper is connected to the AFS vane. The AFS exerts a major influence on the amount of fuel injected.
ATS = air temperature sensor
The ATS is mounted in the AFS inlet tract and measures the air temperature before it enters the inlet manifold. Because the density of air varies in inverse proportion to the temperature, the ATS signal allows more accurate assessment of the volume of air entering the engine. However, the ATS has only a minor correcting effect on ECU output. The open circuit supply to the sensor is at a 5.0 volt reference level and the earth path is through the AFS earth return circuit. The ATS operates on the NTC principle. A variable voltage signal is returned to the ECU based upon the air temperature. This signal is approximately 2.0 to 3.0 volts at an ambient temperature of 20° C and reduces to about 1.5 volt as the temperature rises to around 40° C.
CID sensor = cylinder identification sensor
CO pot = The CO pot mixture adjuster is a three wire potentiometer that allows small changes to be made to the idle CO. A 5.0 volt reference voltage is applied to the sensor and connected to the AFS earth return circuit. The third wire is the CO pot signal.
As the CO pot adjustment screw is turned the change in resistance returns a voltage signal to the ECU that will result in a change in CO. The CO pot adjustment only affects idle CO. Datum position is usually 2.50 volts. On catalyst equipped models, the CO pot has no effect and the CO is thus non-adjustable.
CTS = coolant temperature sensor
The CTS is immersed in the coolant system and contains a variable resistance that operates on the NTC principle. When the engine is cold, the resistance is quite high. Once the engine is started and begins to warm-up, the coolant becomes hotter and this causes a change in the CTS resistance. As the CTS becomes hotter, the resistance of the CTS reduces (NTC principle) and this returns a variable voltage signal to the ECU based upon the coolant temperature. The open circuit supply to the sensor is at a 5.0 volt reference level and this voltage reduces to a value that depends upon the resistance of the CTS resistance. Normal operating temperature is usually from 80° to 100° C. The ECU uses the CTS signal as a main correction factor when calculating ignition timing and injection duration.
The ECU is adaptive to changing engine operating characteristics and constantly monitors the data from the various sensors (ie MAP, ATS, CTS and TPS). As the engine or its components wear, the ECU reacts to new circumstances by adopting the changed values as a correction to the basic Map. When the adaptive map is used in conjunction with the OS, Motronic is able to respond much more quickly and retain tighter control over the changing gases in the exhaust system. During closed loop operation the basic injection value is determined by the values stored in the map for a specific rpm and load. If the basic injection value causes exhaust emissions outside of the Lambda value (ie 0.98 to 1.04 AFR) the mixture would be too rich or too lean and the OS would signal Motronic which in turn will correct the mixture. However, this response takes a little time and so Motronic learns a correction value and adds this 'Adaptive' values to the basic map. From now on, under most operating conditions, the emissions will be very close to Lambda and so, after reference to the OS signal, the ECU will only need to make small corrections to keep it that way. Adaption and correction of the map occurs during the following engine operations.
Idle mixture adjustment
part load mixture adjustment
More details here http://www.opel-scanner.com/files/DME_1.1_1.3.pdf
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