For 1990-2009 cars only
Circuit Description
| • | The powertrain control module (PCM) supplies a voltage of about 0.45 volt between terminals J1-13 and J1-14. If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volt. The oxygen sensor (O2S) varies the voltage within a range of about 1 volt if the exhaust is rich, down through about 0.10 volt if the exhaust is lean. |
| • | The sensor is like an open circuit and produces no voltage when it is below 315°C (600°F). An open sensor circuit or cold sensor causes Open Loop operation. |
| • | If the oxygen sensor pigtail wiring, connector, or terminal are damaged the entire oxygen sensor assembly must be replaced. DO NOT attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have a clean air reference provided to it. This clean air reference is obtained by way of the oxygen sensor wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degrade oxygen sensor performance. Refer to Section 8A-5, Heated Oxygen Sensor (O2S) Repair. |
Conditions for Setting
| • | When one or more of the following DTCs are not present: DTC P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0301, P0302, P0303, P0304, P0441, P0562, P0563, P1171, P1441. |
| • | Engine coolant temperature is greater than 50°C (122°F). |
| • | The engine has been running for greater than 10 seconds. |
| • | The TP angle is between 5-50 percent. |
| • | The air/fuel ratio is between 14.5 and 14.7. |
| • | The engine is operating in Closed Loop. |
| • | The engine has met the TP sensor, Air/Fuel ratio, Closed Loop, and ECT conditions for 50 seconds. |
| • | The O2S voltage is less than 301 mV. |
| • | The above conditions are present for at least 113 seconds. |
Action Taken
| • | Malfunction indicator lamp (MIL) illuminates after one driving cycle with the fault active. |
| • | The vehicle will operate in Open Loop. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after passing three consecutive diagnostic tests. |
| • | A history DTC will clear after 40 consecutive ignition cycles have occurred without a fault. |
| • | History and current DTCs can be cleared by using a scan tool. |
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 loads to confirm. Refer to Fuel System Diagnosis . |
| • | MAP sensor--An output that causes the PCM to sense a lower than normal manifold pressure, high vacuum, can cause the system to go lean. Disconnecting the MAP sensor will allow the PCM to substitute a fixed (default) value for the MAP sensor. If the lean condition is gone when the sensor is disconnected, substitute a known good sensor and recheck. |
| • | Fuel contamination--Water, in even small amounts, near the in-tank fuel pump inlet will be delivered to the injector. The water causes a lean exhaust and can set DTC P0131. |
| • | Sensor harness--Sensor pigtail may be mispositioned and contacting the exhaust manifold. |
| • | Engine misfire--A cylinder will result in unburned oxygen in the exhaust, which could cause DTC P0131. Refer to DTC P0300 Engine Misfire Detected or to the Symptom, Section 6E3-B. |
| • | Cracked oxygen sensor (O2S)--A cracked O2S or poor ground at the sensor could cause a DTC P0131. Refer to Symptoms, Section 6E3-B. |
| • | Plugged fuel filter--A plugged fuel filter can cause a lean condition and cause a DTC P0131 to set. |
| • | Plugged O2S-- A plugged reference port on the O2S will indicate a lower than normal voltage output from the O2S. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Was the On-Board Diagnostic (OBD) System Check perform? | -- | Go to Step 2 | |
2 |
Does the O2S 1 voltage remain below the specified value? | 301 mV | Go to Step 4 | Go to Step 3 |
3 |
Does the O2S 1 voltage remain below the specified value? | 301 mV | Go to Diagnostic Aids | Go to Step 8 |
4 | Disconnect the O2S 1. Does the scan tool indicate O2S 1 voltage within the specified range? | 407-509 mV | Go to Diagnostic Aids | Go to Step 5 |
5 |
Is the O2S 1 signal circuit shorted to ground? | -- | Go to Step 6 | Go to Step 7 |
6 | Repair the O2S 1 signal circuit. Is the action complete? | -- | -- | |
7 | Replace the PCM. Is the action complete? | -- | -- | |
8 | Check the PCM for other DTCs. Are any other DTCs present? | -- | Go to applicable DTC chart | Go to Diagnostic Aids |
