Circuit Description
The Powertrain Control Module (PCM) supplies a voltage of about 0.45 volts to the Oxygen Sensor 1 (O2S 1). The O2S 1 varies the voltage between a range of about 1 volt if the exhaust is rich, down through about 0.10 volt if the exhaust is lean.
The O2S 1 is like an open circuit and produces no voltage when the O2S 1 temperature is below 315°C (600°F). An open O2S 1 circuit or cold sensor causes an Open Loop operation.
Conditions For Running The DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0200, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 not set. |
| • | Air flow is greater than 3 grams per second. |
| • | Engine Coolant Temperature (ECT) is greater than 70°C (158°F). |
| • | Engine is operating in Closed Loop. |
| • | Throttle Position (TP) angle is between 5 percent and 50 percent. |
| • | Engine has been in the above conditions for 20 seconds. |
Conditions For Setting The DTC
O2S 1 voltage is less than 44 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 active. |
| • | The PCM will record the operating conditions at the time that the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information. |
| • | A history DTC stores. |
Conditions for Clearing the MIL/DTC
| • | The malfunction indicator lamp (MIL) will turn OFF after 3 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
| • | The Fuel Pressure - System will run lean if the fuel pressure is too low. Monitor the fuel pressure while driving the vehicle at various road speeds and loads in order to confirm. Refer to Fuel System Diagnosis . |
| • | The 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 (defaulted) value for the MAP sensor. When the lean condition is gone when the sensor is disconnected, substitute a known good sensor and recheck. |
| • | A fuel contamination - Water, in even small amounts, near the fuel pump inlet can be delivered to the fuel injector. The water causes a lean exhaust and a DTC P0131 can set. |
| • | The O2S harness - the O2S 1 pigtail may be mis-positioned and contacting the exhaust manifold. |
| • | An engine misfire A misfire will result in unburned oxygen in the exhaust, which can cause DTC P0131. Go to DTC P0300 Engine Misfire Detected and the Driveability Symptoms. |
| • | A cracked Oxygen sensor (O2S) - A cracked O2S or poor ground at the sensor can cause a DTC P0131. Go to the Driveability Symptoms. |
| • | A plugged fuel filter - A plugged fuel filter can cause a lean condition and cause a DTC P0131 to set. |
| • | A plugged Oxygen Sensor (O2S) - A plugged reference port on the Oxygen Sensor (O2S) will indicate a lower then normal voltage output from the O2S. |
Test Description
The number(s) below refer(s) to the step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.
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This step determines if the DTC P0131 is the result of a hard malfunction or an intermittent condition. It may be necessary to operate the vehicle within the Freeze Frame conditions and Conditions for Setting the DTC in order to duplicate the malfunction that was detected by the PCM.
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This step simulates a DTC P0134. If the PCM senses the change, the PCM and wiring are OK.
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Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Isuzu Technical Communications System (ITCS) information for PCM programming and the Crankshaft Position System Variation Learn for the Crankshaft Position System Variation Learn Procedure.
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If no malfunctions have been found at this point and if no additional DTCs were set, refer to the Diagnostic Aids for additional checks and information.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Does the O2S 1 voltage remain below the specified value? | 52 mV | |||
3 |
Does the O2S 1 voltage stay below specified value? | 52 mV | ||
Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury. Does the scan tool indicate that the O2S 1 voltage is within the specified values? | 399-499 mV | Go to Diagnostic Aids | ||
5 |
Was a repair necessary? | -- | ||
Is the action complete? | -- | -- | ||
7 |
Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury. Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC table | System OK |
