Code No. P0150: Cylinder 2, 3 Oxygen Sensor (Front) System

OPERATION

The sensor signal is inputted to the engine-A/T-ECU (terminal No. 108) from the cylinder 2, 3 oxygen sensor (front) output terminal (terminal No. 4).
The cylinder 2, 3 oxygen sensor (front) (terminal No. 2) is earthed with engine-A/T-ECU (terminal No. 96).

FUNCTION

The cylinder 2, 3 oxygen sensor (front) converts the concentration of oxygen in the exhaust emission into a voltage and inputs the signal to the engine-A/T-ECU.
When the air-fuel ratio is richer than the theoretical air-fuel ratio, the cylinder 2, 3 oxygen sensor (front) outputs a voltage of about 1 V. When it is leaner than the theoretical air-fuel ratio, it outputs a voltage of about 0 V.
In response to the signal, the engine-A/T-ECU controls the fuel injection amount so that the air-fuel ratio can be equivalent to the theoretical air-fuel ratio.

TROUBLE JUDGMENT

Check Conditions

Above 3 minutes later after the engine has started up.
The engine coolant temperature is approximately 80°C or higher.
The engine speed is 1, 200 r/min or more.
During the run at the constant speed on the flat road.
Volumetric efficiency is 25% or more.

Judgment Criteria

When a power voltage of 5 V is applied to the cylinder 2, 3 oxygen sensor (front), the sensor output voltage is 4.5 V or more.

PROBABLE CAUSE

Failed cylinder 2, 3 oxygen sensor (front)
Open/short circuit in cylinder 2, 3 oxygen sensor (front) circuit or loose connector contact
Failed engine-A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list

Refer to Data List Reference Table .

Item 39: Cylinder 2, 3 oxygen sensor (front)

Q. Is the check result normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).

	Go to Step 2 .

STEP 2. Connector check: B-19 cylinder 2, 3 oxygen sensor (front) connector

Q. Is the check result normal?

Go to Step 3 .

Repair or replace.

STEP 3. Perform resistance measurement at B-19 cylinder 2, 3 oxygen sensor (front) connector.

Disconnect connector, and measure at harness side.
Resistance between terminal No. 2 and earth.

OK: 2 Ω or less

Q. Is the check result normal?

Go to Step 7 .

Go to Step 4 .

STEP 4. Connector check: C-113 engine-A/T-ECU connector

Q. Is the check result normal?

Go to Step 5 .

Repair or replace.

STEP 5. Check harness between B-19 (terminal No. 2) cylinder 2, 3 oxygen sensor (front) connector and C-113 (terminal No. 96) engine-A/T-ECU connector.

Check earthing line for open circuit and damage.

Q. Is the check result normal?

Go to Step 6 .

Repair.

STEP 6. M.U.T.-III data list

Refer to Data List Reference Table .

Item 39: Cylinder 2, 3 oxygen sensor (front)

Q. Is the check result normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).

	Replace engine-A/T-ECU.

STEP 7. Perform voltage measurement at B-19 cylinder 2, 3 oxygen sensor (front) connector.

Use special tool test harness (MB991316) to connect connector, and measure at pick-up harness.
Engine: After warm-up
Transmission: P range
Voltage between terminal No. 4 and earth.

OK:
When the engine is 2,500 r/min, the output voltage should repeat 0.4 V or less to 0.6 - 1.0 V alternately.

Q. Is the check result normal?

Go to Step 10 .

Go to Step 8 .

STEP 8. Check cylinder 2, 3 oxygen sensor (front) itself

Check cylinder 2, 3 oxygen sensor (front) itself (Refer to ).

Q. Is the check result normal?

	Go to Step 9 .

	Replace cylinder 2, 3 oxygen sensor (front).

STEP 9. Connector check: C-113 engine-A/T-ECU connector

Q. Is the check result normal?

Check output line for damage.

Repair or replace.

STEP 10. Perform voltage measurement at C-113 engine-A/T-ECU connector.

Measure engine-A/T-ECU terminal voltage.
Transmission: P range
Engine: After warm-up
Voltage between terminal No. 108 and earth.

OK:
When the engine is 2,500 r/min, the output voltage should 0.4 V or less to 0.6 - 1.0 V alternately.

Q. Is the check result normal?

Go to Step 12 .

Go to Step 11 .

STEP 11. Connector check: C-113 engine-A/T-ECU connector

Q. Is the check result normal?

Check output line for open circuit.

Repair or replace.

STEP 12. Connector check: C-113 engine-A/T-ECU connector

Q. Is the check result normal?

Repair or replace.