Oxygen concentration sensor (with heating) (Mitsubishi Matrix)

The engine control unit uses the signals from the oxygen sensor to regulate the composition of the fuel-air mixture, ensuring optimum fuel economy and reducing harmful emissions. Based on the information on the oxygen content in the exhaust gases, coming from the front oxygen sensor, the degree of enrichment or leanness of the fuel-air mixture supplied to the engine cylinders is determined. Based on the signals from the rear oxygen sensor, the efficiency of the catalytic converter of exhaust gases is determined. The ECU calculates the efficiency of the converter by comparing the signal from the rear oxygen sensor with the signal from the front sensor.

The normal oxygen sensor signal voltage is constantly changing around 500 mV, and the signal frequency of the front sensor is at least 5 Hz at 2500 min⁻¹. Due to the action of the catalytic converter, the signal frequency of the rear oxygen sensor is lower than the signal frequency of the front oxygen sensor. If the signal frequency of the rear oxygen sensor is the same as the signal frequency of the front oxygen sensor for a long period of time, this indicates a decrease in the efficiency of the catalytic converter or a malfunction of the engine fuel system.

Conditions for storing fault codes

The ECU stores a fault code and the engine management system malfunction indicator lamp comes on when an open or short circuit to ground in the injector circuit is detected in two driving cycles.

Code P0130

In each driving cycle after the engine is started, the ECU checks the front oxygen sensor once for 5 seconds. If the front oxygen sensor signal voltage is not within the range of 0 to +380 mV in two driving cycles, while the rear oxygen sensor signal voltage is above 350 mV, the ECU sets a malfunction code and turns on the engine management system malfunction indicator lamp. This code indicates that the ECU has detected a malfunction in the front oxygen sensor.

Code P0136

After the system enters the closed control loop and the engine has been running for 3 minutes, the ECU checks the signal voltage of the rear oxygen sensor. If the signal voltage of the rear oxygen sensor is not within 400-500 mV in two driving cycles, the ECU sets a malfunction code and turns on the engine management system malfunction indicator lamp. This code indicates the presence of abnormal readings from the rear oxygen sensor or the ECU after the engine has been warmed up for 3 minutes.

Code P0131

Three minutes after the front HO2S heating is turned on, the ECM continuously measures the front HO2S signal voltage at 0.5 s intervals. If the front HO2S signal voltage is below 50 mV for 0.5 s in two driving cycles, the ECM sets the P0131 code and turns on the engine management system malfunction indicator lamp. This code indicates that the front HO2S or the ECM has detected a severely lean mixture.

Code P0131

After the system enters the closed control loop and after 3 minutes of engine operation, the ECU checks the signal voltage of the rear oxygen sensor for 0.5 s. If the signal voltage of the rear oxygen sensor is below 50 mV in two driving cycles, the ECU sets the code P0137 and turns on the engine management system malfunction indicator lamp. The output of this code indicates an extremely low signal voltage of the rear oxygen sensor.

Code P0132

Three minutes after the front oxygen sensor heater is turned on, the engine control module continuously measures the front oxygen sensor signal voltage at 0.5 s intervals. If the front oxygen sensor voltage exceeds 1.058 V for 0.5 s in two driving cycles, the ECM sets the code P0132 and the engine management system malfunction indicator lamp comes on. This code indicates that the fuel-air mixture is too rich.

Code P0138

After the system enters the closed control loop and after 3 minutes of engine operation, the ECU checks the signal from the rear oxygen sensor for 0.5 seconds. If the voltage of the rear oxygen sensor signal exceeds 1.058 V in two driving cycles, the ECU outputs the code P0138 and the engine management system malfunction indicator lamp comes on. Output of this code indicates excessively high voltage of the rear oxygen sensor signal.

Code P0133

The engine control unit stores the code P0133 in its memory and the engine management system malfunction indicator lamp comes on if the ECU does not detect the parameters listed below in two driving cycles.

1. Within 2 minutes, the ECU must determine that the fuel mixture compensation coefficient is greater than 85% or less than 95%.

2. The ECU must make some correction to the fuel-air mixture when:

[The article is borrowed from the website: HyundaiBook.ru]

• the crankshaft speed is within 1600–3200 min⁻¹;
• engine load is within 1.35–3.4 ms;
• catalytic converter temperature above 372°C;
• the system is in a closed control loop.

The output of this code indicates that the ECU does not properly correct the air-fuel mixture composition based on signals from the front oxygen sensor or does not correct it with the required frequency after the engine warms up or during normal engine operation.

Code P0134

After 3 minutes of engine operation, the ECU checks the signal voltage of the front oxygen sensor. If the signal voltage of the front oxygen sensor is not within 400-600 mV for 5 seconds in two driving cycles, the ECU issues a code and the engine management system malfunction indicator lamp lights up. The output of this code indicates that after the engine warms up, the signal voltage of the front oxygen sensor is not within the required limits.