Lambda sensor installed at exhaust manifold is planar ZrO2 dual cell type and it senses O2 density of exhaust gas for accurate EGR control through fuel correction. It also limits smoke which is generated by reach air-fuel mixture at engine maximum loading condition. ECM controls pumping current in order to fit ?-value from linear O2 sensor to 1.0.
Lean air-fuel mixture(1.0
Rich air-fuel mixture(0.9
This performance is the most active and fast at normal operating temp.(450?~600?) thus, in order to reach normal operating temp. and last at that temp., heater(heating coil) is integrated with Lambda sensor.
Heater coil is controlled by ECM as PWM. the resistance of heater coil is low when coil is cold thus, current through it increases while resistance is high when coil is hot thus, current decreases. With this principle, Lambda sensor temp. is measured and Lambda sensor heater operation varies based on the data.
P2251 is set when ground line(terminal 3) is opened. This code is due to the problem of Lamda sensor circuit.
Item
Detecting Condition
Possible Cause
DTC Strategy
? Voltage monitoring
? Lambda sensor circuit
? Lambda sensor component
Enable Conditions
? Engine running
Threshold Value
? Open in Lamda sensor ground circuit
Diagnostic Time
? 2.0 sec.
Fail Safe
Fuel Cut
NO
EGR Off
Fuel Limit
Check Lamp
? value
0.65
0.70
0.80
0.90
1.01
1.18
1.43
1.70
2.42
Air
Pumping current
-2.22
-1.82
-1.11
-0.50
0.00
0.33
0.37
0.94
1.38
2.54