Circuit Description
The powertrain control module (PCM) supplies a voltage of about 447 mV between the heated oxygen sensor (HO2S) 1 high signal and the low signal circuit. The HO2S 1 varies the voltage within a range of about 1000 mV if the exhaust is rich, down through about 100 mV if the exhaust is lean.
The sensor is like an open circuit and produces no voltage when below 315°C (600°F).
Do not attempt to repair the HO2S. Replace the entire HO2S if the following conditions exist:
| • | Damaged wiring |
| • | Damaged electrical connector |
| • | Damaged terminals |
Conditions For Running The DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0336, P0440, P0446, P0452, P0453, P0507, P0601, P0602, P0604, P0606, P1120, P1220, P1221, P1271, P1275, P1280, P1484, P1512, P1514, P1515, P1516, P1621, P1635, P1639, P1680, or P1681 are not set. |
| • | The fuel level sensor is more than 10 percent. |
| • | The ignition 1 signal is more than 10 volts. |
| • | The engine run time is more than 10 seconds. |
| • | The accelerator pedal position (APP) indicated angle is more than 1.2 percent. |
| • | The engine coolant temperature (ECT) sensor is more than 70°C (158°F). |
| • | The loop status is closed. |
| • | The throttle position (TP) indicated angle is between 15-50 percent. |
| • | The manifold absolute pressure (MAP) sensor is more than 25 kPa. |
| • | The above conditions have been met for 3.8 seconds. |
Conditions For Setting The DTC
The HO2S 1 signal voltage is less than 52 mV for 125 seconds.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the malfunction present. |
| • | The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame/Failure Records buffers. |
| • | A history DTC stores. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm up cycles without a fault. |
| • | Use a scan tool to clear the DTCs. |
Diagnostic Aids
| • | Fuel pressure--System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving the vehicle at various road speeds and/or loads to confirm. Refer to Fuel System Diagnosis . |
| • | MAP sensor--An output that causes the PCM to sense a lower than normal manifold pressure, or high vacuum, can cause the system to go lean. Disconnecting the MAP sensor will allow the PCM to substitute a fixed, or default, value for the MAP sensor. If the lean condition is gone when the MAP sensor is disconnected, refer to DTC P0105 for further diagnosis. |
| • | Fuel contamination--Water, in even small amounts, near the in-tank fuel pump inlet, can be delivered to the injector. The water causes a lean exhaust and can set a DTC P0131. |
| • | Sensor harness--The HO2S 1 sensor pigtail may be mis-positioned and contacting the exhaust manifold. |
| • | Engine misfire--A misfiring cylinder will result in unburned oxygen in the exhaust, which could cause a DTC P0131. Refer to DTC P0300 and/or Symptoms - Engine Controls . |
| • | Cracked heated oxygen sensor (HO2S 1)--A cracked HO2S 1 sensor could cause a DTC P0131. Refer to Symptoms - Engine Controls . |
| • | Plugged fuel filter--A plugged fuel filter can cause a lean condition and cause a DTC P0131 to set. |
| • | Plugged oxygen sensor (HO2S 1)--A plugged reference port on the HO2S 1 will indicate a lower then normal voltage output from the HO2S 1 sensor. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 |
Does the voltage remain below the specified value? | 52 mV | Go to Step 4 | Go to Step 3 |
3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | |
4 |
Does the scan tool indicate HO2S 1 voltage is less than the specified value? | 400 mV | Go to Step 5 | Go to Step 7 |
5 | Test the HO2S high signal circuit for a short to ground or a short to the HO2S low signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 6 |
6 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
7 | Inspect the vehicle for any of the conditions in Diagnostic Aids. If no problem is found, replace the HO2S . Refer to Heated Oxygen Sensor 1 Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
8 |
Does the DTC run and pass? | -- | Go to Step 9 | Go to Step 2 |
9 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
