Nissan Qashqai J11. Manual - part 183
ECH-30
< SYSTEM DESCRIPTION >
[HRA2DDT]
SYSTEM
The richness is managed by heated oxygen sensors shown in the following scheme:
Two sensors measure the combustion efficiency:
Heated Oxygen Sensor 1
The heated oxygen sensor 1 enables the richness closed loop mode. This is a differential sensor and the rich-
ness signal directly depends on the information given by this component:
• Lean (less fuel than air) if the voltage is under 450 mV, so mixture needs an enrichment.
• Rich (more fuel than air) if the voltage is above 450 mV, so mixture needs a richness reduction.
Heated Oxygen Sensor 2
The heated oxygen sensor 2 enables the application of the richness double loop mode and diagnosis of cata-
lyst. Its working technology is the same as the heated oxygen sensor 1.
To be operational very quickly, theses sensors need to be warmed by electric signal and exhaust gas.
The richness regulation is managed by the heated oxygen sensor 1. It consists in applying a correction on the
injection time which depends on the richness states.
Those states depend on the engine speed and engine load. In closed loop mode, fuel injected mass is regu-
lated by the information given by heated oxygen sensors (around reference point). In open-loop mode, rich-
ness is no more regulated and is specific to the mode (above reference point). In full load, richness increase in
order to have the best performance (maximal richness).
Closed loop richness mode is a regulation system using heated oxygen sensor information to quantify the fuel
injected mass; it enables the engine to stay in the catalytic working window, which reduces pollutant emis-
sions. Those sensors (heated oxygen sensor 1 and 2) reflect efficiency of the combustion. More precisely, if
the mixture lacks fuel (lean mixture) the system will then increase the fuel rate, in the opposite case (rich mix-
ture) the fuel rate will be decreased.
The richness double loop regulation is managed by the heated oxygen sensor 2. It consists in computing one
more correction, added to the richness in order to have the best three way catalyst efficiency. For its activation,
the driver has to run nearly 1.5 minutes with a warm running engine out of the idle speed state.
The richness management also includes richness adaptation function.
It consists in learning the injectors lift and wearing effects on richness basic settings. It also shifts the engine
richness mean value around the reference point with a correction, directly modifying the injection time.
The richness is affected by the ‘wall wetting’ phenomena (deposit of a fuel film in the intake ports). ECM com-
pensates the effects by a correction on the fuel injected mass set point.
In order to respect pollutants emissions rules, a gasoline engine needs a catalyst.
The catalyst warm-up quickly enables to trigger this component. There are different phases during this cycle;
several of them affecting richness (richness increased) especially in cold temperature conditions.
AFTER TREATMENT SYSTEM
JPBIA5640GB