Component Location
General Description
Lambda sensor is so called wide range oxygen sensor and installed at exhaust manifold. It senses O2 density of exhaust gas for accurate EGR control through fuel correction. It also limits smoke which is generated by rich air-fuel mixture at engine maximum loading condition. ECM controls pumping current in order to fit ?-value from lambda O2 sensor to 1.0. If the ECM supplies the more current to lambda sensor, oxygen in the exhaust gas is thin or If the ECM take the current from lambda sensor, ECM judges O2 density in the exhaust gas is getting denser.
?Lean air-fuel mixture(1.0
?Rich air-fuel mixture(0.9
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.This performance is the most active and fast at normal operating temp.(780?) 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 when the temperature of lambda sensor is lower than target temperature(780?). Resistance of heater wire is in proportion to temperature and amount of current is in inverse proportion to temperature. ? sensor measured temperature by using this property and ECM controls heater in accordance with temperature measured by ? sensor. After warming-up, if the temperature of lambda sensor reaches 780?, the duty for the heater coil is controlled within 2 ~ 98%. During the acceleration, temperature of lambda sensor is momentarily increase to 786? or decrease to 774? due to exhaust gas.
noteIn case of replacing lambda sensor, perform the "COMPONENT CHANGE ROUTINE" procedure with scan tool. If the "COMPONENT CHANGE ROUTINE" procedure has not completed until automatic learning completed, it may cause vehicle performance and exhaust gas problem.
DTC Description
DTC P2251 is set when 'Ground' circuit in ? sensor is short to battery / ground or open. DTC "P2238" or "P2239" is retrieved together or "P2238, P2239" and "P2251" is set by abnormal signal is detected at 'Current adjust' and 'Ground'. If ECM detects 'Voltage nernst' or 'Current pump' is faulty.
DTC Detecting Condition
Item | Detecting Condition | Possible Cause |
DTC Strategy | Voltage monitoring
| ? sensor circuit.
? sensor component.
|
Enable Conditions | Engine Running (After lambda sensor is completely warmed up)
|
Threshold Value | 'Ground' is short to battery.
'Ground' is short to ground.
'Ground' is open.
|
Diagnostic Time | 2 sec.
|
Fail Safe | Fuel cut | NO | -
|
EGR Off | NO |
Fuel Limit | NO |
Check Lamp | OFF |
Specification
? value | 0.65 | 0.7 | 0.8 | 0.9 | 1.01 | 1.18 | 1.43 | 1.7 | 2.42 | Air |
Pumping current | -2.22 | -1.82 | -1.11 | -0.5 | 0 | 0.33 | 0.67 | 0.94 | 1.38 | 2.54 |
Diagnostic Circuit Diagram
Signal Waveform & Data
1. The voltage of a sensor when IG key "ON" and engine running. Its voltage is approximately 2.9 V.
2. The waveform of sensor ground when IG key "ON" and engine running. Its voltage is approximately 2.5 V.
3. The waveform of a sensor signal when IG key "ON" and engine running. Its voltage is approximately 2.0 V.
4. The waveform of a sensor pumping when IG key "ON" and engine running. Its voltage is approximately 2.0 V.