OPERATION
- The sensor signal is inputted to the engine-A/T-ECU (terminal No. 109) from the cylinder 1, 4 oxygen sensor (front) output terminal (terminal No. 4).
- The cylinder 1, 4 oxygen sensor (front) (terminal No. 2) is earthed with engine-A/T-ECU (terminal No. 96).
FUNCTION
- The cylinder 1, 4 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 1, 4 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 infection 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
82°C or higher.
- The engine speed is 1200 r/min or more.
- The monitoring time is 5 seconds.
Judgment Criteria
- When the cylinder 1, 4 oxygen sensor (front) output voltage is 0.2 V or less and a power voltage of 5 V is applied to the cylinder 1, 4 oxygen sensor (front) in the engine-A/T-ECU, the sensor output voltage is 4.5 V or more.
- To be monitored once per driving cycle.
Check Conditions
- The engine speed is 1200 - 3000 r/min.
- The engine coolant temperature is approximately
60°C or higher.
- Volumetric efficiency is 20 - 60%.
- During the air-fuel ratio feedback control
Judgment Criteria
- When the cylinder 1, 4 oxygen sensor (front) output frequency is 6 or less for 10 seconds on the average.
PROBABLE CAUSE
- Failed cylinder 1, 4 oxygen sensor (front)
- Open/short circuit in cylinder 1, 4 oxygen sensor (front) circuit or loose connector contact
- Failed engine-A/T-ECU
)
Q: Is the check result normal?
YES:
Go to Step 3 
.NO: Repair.
- 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?
YES:
Go to Step 7 .NO: Go to Step 4
.)
Q: Is the check result normal?
YES:
Go to Step 5 .NO: Repair.
NOTE: Before checking harness, check intermediate connector C-16, and repair if necessary.
- Check earthing line for open circuit and damage.
Q: Is the check result normal?
YES:
Go to Step 6 .NO: Repair.
- 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 to 0.8 V alternately.
Q: Is the check result normal?
YES:
Go to Step 10 .NO: Go to Step 8
.
Q: Is the check result normal?
YES:
- Check and repair harness between B-122 (terminal No. 4) Cylinder 1, 4 oxygen sensor (front) connector and C-137 (terminal No. 109) engine-A/T-ECU connector.
- Check output line for damage.
- Measure engine-A/T-ECU terminal voltage.
- Transmission: P range
- Engine: After warm-up
- Voltage between terminal No. 109 and earth.
OK:
- When the engine is 2,500 r/min, the output voltage should repeat 0 to 0.8 V alternately.
Q: Is the check result normal?
YES:
Go to Step 12 .NO: Go to Step 11
.
Q: Is the check result normal?
YES:
- Check and repair harness between B-122 (terminal No. 4) oxygen sensor (front) connector and C-137 (terminal No. 109) engine-A/T-ECU connector.
- Check output line for open circuit.
Q: Is the check result normal?
YES:
- Go to Step 6 .