Federal
Heated Oxygen Sensor (front) Heater Circuit:
Connector: C-51 <M/T>, C-52 <A/T>:
CIRCUIT OPERATION
- Power is supplied from the MFI relay (terminal 1) to the heated oxygen sensor (front) heater.
- The ECM (terminal 3)
TECHNICAL DESCRIPTION
- The ECM
DTC SET CONDITIONS
Check Conditions
- Engine coolant temperature is higher than 20°C (68°F).
- While the heated oxygen sensor (front) heater is on.
- Battery positive voltage is between 11 and 16 volts.
Judgment Criteria
- Heater current of the heated oxygen sensor (front) heater has continued to be lower than 0.2 ampere or higher than 3.5 amperes for 6 seconds.
- One monitor during one drive cycle
TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Open or shorted heated oxygen sensor (front) heater circuit.
- Open circuit in heated oxygen sensor (front) heater.
- ECM failed.
- PCM failed.
DIAGNOSIS
Required Special Tool:
MB991658: Test Harness Set
STEP 1. Check the heated oxygen sensor (front).
1. Disconnect heated oxygen sensor (front) connector C-24 and connect test harness special tool, MB991658, to the connector on the heated oxygen sensor (front) side.
2. Measure the resistance between heated oxygen sensor (front) connector terminal 3 and terminal 4.
Standard value: 11 - 18 ohms [at 20°C (68°F)]
If within specifications, go to Step 2.
If not within specifications, replace the heated oxygen sensor (front). Then go to Step 7.
STEP 2. Check the power supply line at heated oxygen sensor (front) connector C-24.
1. Disconnect connector C-24 and measure at the harness side.
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 3 and ground.
- Voltage should be battery positive voltage.
4. Turn the ignition switch to "LOCK" (OFF) position.
If within specifications, go to Step 3.
If not within specifications, repair the harness wire between MFI relay connector A-21X and heated oxygen sensor (front) connector C-24. Then go to Step 7.
STEP 3. Check harness connector C-24 at the heated oxygen sensor (front) for damage.
If harness connectors C-24 is in good condition, go to Step 4.
If harness connector C-24 is damaged, repair or replace it.
Refer to Harness Connector Inspection. Then go to Step 7.
STEP 4. Check the circuit at ECM connector C-51
1. Disconnect connector C-51
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 3 and ground.
- Voltage should be battery positive voltage.
4. Turn the ignition switch to "LOCK" (OFF) position.
If within specifications, go to Step 5.
If not within specifications, repair the harness wire between heated oxygen sensor (front) connector C-24 and the ECM connector C-51
STEP 5. Check harness connector C-51 at the ECM
If harness connectors C-51
If harness connector C-51
STEP 6. Check the terminal voltage at ECM connector C-51
1. Connect connector C-51
2. Start the engine and run at idle.
3. Measure voltage between terminal 3 and ground.
Standard value:
9 - 11 V (Engine: warm idle)
9 - B+ (Engine: revving)
4. Turn the ignition switch to "LOCK" (OFF) position. If within specifications, this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope With Intermittent Malfunction.
If not within specifications, 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 6 - Other Monitor.
2. Read the diagnostic trouble code, and confirm that diagnostic trouble code P0135 does not reset.