OXYGEN SENSOR VOLTAGE (#05)
Reading #05 on the XR25 : the value read is the voltage sent to the computer by the oxygen sensor; it is ex-
pressed in volts (the value actually varies between 0 and 1 000 millivolts).
When the engine is in the loop phase, the voltage value should oscillate rapidly and should be between
50±50 mV (lean mixture) and 850 ± 50 mV (rich mixture) and vice versa.
The smaller the gap between the upper and lower values, the poorer the information from the sensor (the
gap is usually at least 500 mV).
RICHNESS CORRECTION (#35)
The value given under # 35 on the XR25 represents the average value of richness corrections made by the
computer depending on the richness of the burnt mixture as seen by the oxygen sensor (the oxygen sensor ac-
tually analyses the oxygen content of the exhaust gases directly from the richness of the burnt mixture).
The richness correction has a centre point of 128 with thresholds of 0 and 255 (experience has shown that un-
der normal operating conditions # 35 is located close to 128 with only a small amount of variation).
- Value less than 128 : request for mixture to be made leaner.
- Value greater than 128 : request for mixture to be made richer.
ENTRY INTO RICHNESS REGULATION MODE
Loop phase
Richness regulation begins after the timed starting period :
- for no load, if the coolant temperature has reached :
•46°C for the E7J engine ,
•30°C for the D7F engine.
- outside no load conditions if the coolant temperature is greater than :
•+ 20°C for the E7J, engine
•+ 20°C for the D7F engine.
The timed starting period is dependent on the coolant temperature :
- at 20°C it is a maximum of :
•3 minutes for the E7J engine,
•1 minute 20 seconds for the D7F engine,
- at 80°C it is a maximum of :
•1 minute 30 seconds for the E7J engine,
•35 seconds for the D7F engine,
If richness regulation has not yet started, #35 = 128
INJECTION
Richness regulation
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INJECTION
Richness regulation
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Non-loop mode
When richness regulation is occurring, the operating phases when the computer ignores the voltage informa-
tion from the oxygen sensor are:
- Full load: #35 = variable and greater than 128
- Sharp acceleration: #35 = variable and greater than 128
- Deceleration with no load information (injection cut) : #35 = 128
- Oxygen sensor fault: #35 = 128
DEFECT MODE IN THE EVENT OF AN OXYGEN SENSOR FAULT
If the voltage from the oxygen sensor is incorrect (# 05 varies only slightly or not at all) during richness regu-
lation, the computer will only enter defect mode (# 35 = 128) if the fault has been present for 3 to 5 minutes.
The fault will be memorised in this case only.
If an oxygen sensor fault is present and recognised and if the fault has already been stored, the system enters
the open loop mode directly (# 35 = 128)
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