3.
Is the problem found?
 | ▶ Repair the trouble causing part and go to "Verification of Vehicle Repair". |
 | ▶ Go to "Power Circuit Inspection". |
Lambda sensor installed at exhaust manifold is linear Lambda sensor 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 λ-value from linear Lambda sensor to 1.0.
Lean air-fuel mixture(1.0<λ<1.1) : ECM supplies pumping current to Lambda sensor (+pumping current) and activates it for Lambda sensor to have the characteristic at λ=1.0 (0.0 pumping current). With the value of pumping current supplied to Lambda sensor, ECM detects O2 density of exhaust gas.
Rich air-fuel mixture(0.9<λ<1.0) : ECM takes away pumping current from Lambda sensor (-pumping current) and deactivates it for Lambda sensor to have the characteristic at λ=1.0 (0.0 pumping current). With the value of pumping current taken away from Lambda sensor, ECM detects O2 density of exhaust gas.
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.
P0031 is set when open or short to ground in Lambda sensor control circuit is detected for more than 5.0 sec. at Lambda sensor heater control condition. This code is due to 1)open or short to ground in heater control circuit or 2)Lambda sensor heater internal short.
Item | Detecting Condition | Possible Cause | ||
DTC Strategy | ● Voltage monitoring | ● Lamda sensor heater circuit ● Lamda sensor component | ||
Enable Conditions | ● Engine running | |||
Threshold Value | ● Short to GND in Lamda sensor heater control circuit ● Open in Lamda sensor heater control circuit | |||
Diagnostic Time | ● 5.0 sec. | |||
Fail Safe | Fuel cut | NO | ||
EGR Off | NO | |||
Fuel Limit | NO | |||
Check Lamp | NO | |||
Temperature (℃) | Lambda sensor heater resistance(Ω) | Temperature (℃) | Lambda sensor heater resistance(Ω) | Lambda sensor heater control Hz |
20 | 9.2 | 400 | 17.7 | 100 Hz |
100 | 10.7 | 500 | 19.2 | |
200 | 13.1 | 600 | 20.7 | |
300 | 14.6 | 700 | 22.5 |
Fig.1) Waveform of Lambda sensor heater power. It is battery voltage and Lambda sensor heater control at idle.
Electrical systems consist of a lot of harness and connectors, poor connection of terminals can cause various problems and damge of component.
Perform checking procedure as follows.
Check damage of harness and terminals : Check terminals for contact resistance, corrosion and deformation.
Check connecting condition of ECM and component connector : Check terminal seperation, damage of locking device and connecting condition between terminal and wiring.
Disconnect the pin which requires checking at male connector and insert it to the terminal at female connector for checking connecting condition. ( after checking, reconnect the pin at correct position. )
Is the problem found?
| ▶ Repair the trouble causing part and go to "Verification of Vehicle Repair". |
| ▶ Go to "Power Circuit Inspection". |
IG KEY "OFF", ENGINE "OFF".
Disconnect Lambda sensor connector.
IG KEY "ON".
Measure the voltage between heater power terminal of Lambda sensor harness connector and chassis ground.
Specification : 11.0V~13.0V ( Main relay ON power )
Is the measured voltage within the specification?
| ▶ Go to "Control Circuit Inspection". |
| ▶ Repair open in Main relay power circuit and FUSE in E/R JUNCTION BOX and go to "Verification of Vehicle Repair". |
Check Lambda sensor heater control circuit voltage
IG KEY "OFF", ENGINE "OFF".
Disconnect Lambda sensor connector.
IG KEY "ON".
Measure the voltage between heater control terminal of Lambda sensor harness connector and chassis ground.
Specification : 2.0V~2.5V
Is the measured voltage within the specification?
| ▶ Go to "Component Inspection". |
| ▶ No voltage is detected : Go to "2. Check open in Lambda sensor heater control circuit" as follows. ▶ High voltage is detected : Repair short to battery in control circuit and go to "Verification of Vehicle Repair". |
Check open in Lambda sensor heater control circuit
IG KEY "OFF", EFNGINE "OFF".
Disconnect Lambda sensor connector and ECM connector.
Check continuity between heater control terminal of Lambda sensor harness connector and ECM harness connector.
Specification : Continuity (below 1.0Ω )
Is the measured resistance within the specification?
| ▶ Repair short to ground in control circuit and go to "Verification of Vehicle Repair". |
| ▶ Repair open in Lambda sensor heater control circuit and go to "Verification of Vehicle Repair". |
Check Lambda sensor component heater coil resistance.
IG KEY "OFF", ENGINE "OFF".
Disconnect Lambda sensor connector.
Check continuity between heater power terminal and heater control of Lambda sensor connector (component side).
Specification : Refer to "Specification" of "General Information"
Is the measured resistance within the specification?
| ▶ Go to "Verification of Vehicle Repair". |
| ▶ Replace Lambda sensor and go to "Verification of Vehicle Repair". |
After a repair, it is essential to verify that the fault is corrected.
After connecting GDS select "Diagnostic Trouble Codes(DTCs)" mode to and then clear DTC.
Drive the vehicle within DTC Enable conditions in General information.
After selecting "Diagnostic Trouble Codes(DTCs)" mode and check DTC is recorded again.
Are any DTCs recorded ?
| ▶ Go to the DTC guide of recorded NO. in GDS |
| ▶ System operates within specification. |
