Federal
Heated Oxygen Sensor (rear) Circuit:
CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal 75)
- Terminal 2 of the heated oxygen sensor (rear) is grounded with ECM (terminal 92)
TECHNICAL DESCRIPTION
- The output signal of the heated oxygen sensor (front) is counter balanced by the output signal of the heated oxygen sensor (rear).
- The ECM or PCM checks for an open circuit in the heated oxygen sensor (rear) output line.
DTC SET CONDITIONS
Check Conditions
- Heated oxygen sensor (rear) signal voltage has continued to be 0.15 volt or lower for three minutes or more after starting the engine.
- Engine coolant temperature is higher than 82 °C (180 °F).
- Engine speed is higher than 1,200 r/min.
- Volumetric efficiency is higher than 25 percent.
- Monitoring time: 7 seconds.
Judgment Criteria
- Input voltage supplied to the ECM or PCM interface circuit is higher than 4.5 volts for four seconds when 5 volts is applied to the heated oxygen sensor (rear) output line via a resistor.
- One monitor during one drive cycle.
Check Conditions
- Heated oxygen sensor signal voltage remains 0.15 volt or less for at least three minutes after the engine starts.
- Engine coolant temperature is approximately 82 °C (180 °F) or more.
- Engine speed is approximately 1,200 r/min or more.
- Volumetric efficiency is 25% or more.
- Volume air flow sensor output frequency is 88 Hz or more.
- At least twenty seconds have passed since fuel shut off control was canceled.
- The heated oxygen sensor outputs 0.5 volts or more.
- Monitoring time: 10 seconds.
Judgement Criteria
- When air-fuel ratio becomes richer 15% for ten seconds, the heated oxygen sensor output voltage is 0.15 volt or less.
- Only one monitor during one drive cycle.
Check Conditions
- Engine coolant temperature is approximately 82 °C (180 °F) or more.
- Atmospheric pressure 76 kPa (11 psi) or more.
- The heated oxygen sensor (front) is active.
Judgement Criteria
- The heated oxygen sensor (rear) output voltage is 0.4 volt or more when fuel begins to be shut off. Then at least one second elapses before the voltage reduces to 0.15 volt or less while fuel is being shut off.
or
- The heated oxygen sensor (rear) output voltage is 0.15 volt or more when fuel begins to be shut off. Then at least three seconds elapse before the voltage reduces to 0.15 volt or less while fuel is being shut off.
TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Heated oxygen sensor (rear) failed.
- Open circuit in heated oxygen sensor (rear) output line.
- Open circuit in heated oxygen sensor (rear) ground line.
- ECM failed.
- PCM failed.
DIAGNOSIS
Required Special Tools:
MB991502: Scan Tool (MUT-II)
MB991658: Test Harness Set
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
STEP 1. Using scan tool MB991502, check data list item 59: Heated Oxygen Sensor (rear).
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 59, Heated Oxygen Sensor (rear).
- Warm up the engine. When the engine is revved, the output voltage should repeat 0 volt and 0.6 to 1.0 volt alternately.
If the checks above meet the specification, this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope With Intermittent Malfunction.
If the checks above do not meet the specification, go to Step 2.
STEP 2. Check the heated oxygen sensor (rear).
1. Disconnect heated oxygen sensor (rear) connector C-21 and connect test harness special tool, MB991658, to the connector on the heated oxygen sensor (rear) side.
2. Warm up the engine until engine coolant is 80 °C (176 °F) or higher.
CAUTION: Be very careful when connecting the jumper wires; incorrect connection can damage the heated oxygen sensor (rear).
3. Use jumper wires to connect terminal 3 of the heated oxygen sensor (rear) connector to the positive battery terminal and terminal 4 to the negative battery terminal.
4. Connect a digital voltmeter between terminal 1 and terminal 2.
5. While repeatedly revving the engine, measure the heated oxygen sensor (rear) output voltage.
Standard value: 0.6 - 1.0 V
If within specifications, go to Step 3.
If not within specifications, replace the heated oxygen sensor (rear).
Then go to Step 7.
STEP 3. Check harness connector C-21 at the heated oxygen sensor (rear) for damage.
If harness connector C-21 is in good condition, go to Step 4.
If harness connector C-21 is damaged, repair or replace it.
Refer to Harness Connector Inspection.
Then go to Step 7.
STEP 4. Check harness connector C-38 at the ECM
If harness connectors C-38
If harness connectors C-38
Refer to Harness Connector Inspection.
Then go to Step 7.
STEP 5. Check the harness wire between heated oxygen sensor (rear) connector C-21 and ECM connector C-38
If the wire between heated oxygen sensor (rear) connector C-21 and the ECM connector C-38
If the wire between heated oxygen sensor (rear) connector C-21 and ECM connector C-38
STEP 6. Replace the heated oxygen sensor (rear).
1. Replace the heated oxygen sensor (rear).
2. Carry out a test drive with the drive cycle pattern. Refer to Procedure 4 - Heated Oxygen Sensor Monitor and Procedure 6 - Other Monitor.
3. Check for the diagnostic trouble code (DTC).
If DTC P0136 is not output, the inspection is complete.
If DTC P0136 is output, replace the ECM or PCM. Then go to Step 7.
STEP 7. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 4 - Heated Oxygen Sensor Monitor and Procedure 6 - Other Monitor.
2. Read the diagnostic trouble code, and confirm that diagnostic trouble code P0136 does not reset.