DTC P0131 O2S Circuit Low Voltage Sensor 1. Chevrolet S10 Pickup

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1996 🢒 S10 Pickup - 2WD 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 DTC P0131 O2S Circuit Low Voltage Sensor 1

Handling ESD Sensitive Parts Notice
Engine Controls Components
Pre and Post Oxygen Sensors
OBD II Symbol Description Notice

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 Setting The DTC

•	The engine coolant temperature is greater than 70° C (158° F)

•	The TP angle is between 5 % and 50 %.

•	The TP angle is between 10 % and 50 % (manual).

•	The Air/Fuel ratio is between 14.5 and 14.7

•	The engine is operating in a Closed Loop.

•	The O2S 1 voltage is less than 43 mV for greater than 125 seconds (auto).

•	The O2S 1 voltage is less than 43 mV for greater than 118 seconds (manual).

•	When one or more of the following DTCs are not set, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0300, P0301, P0302, P0303, P0304, P0506, P0507, P1406, P1441.

Action Taken When the DTC Sets

•	The malfunction indicator lamp (MIL) will illuminate.

•	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. Go to Fuel System Pressure Test .

•

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.

Whenever the oxygen sensor pigtail wiring, connector or terminal are damaged, replace the entire oxygen sensor assembly. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, the O2S must have a clean air reference provided. This clean air reference is obtained by way of the oxygen sensor wires. Any attempt to repair the O2S sensor wires, connectors or terminals could result in the obstruction of the air reference degrading the performance of the oxygen sensor.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This information on the scan tool can be referred to later.

Before replacing the PCM, check terminals for improper mating, broken locks, or physical damage to the wiring harness. Reprogram the replacement PCM. Refer to the latest Techline information for programming procedures.

Step	Action	Value(s)	Yes	No
1	Was the Powertrain On-Board Diagnostic (OBD) System Check performed?	--	Go to Step 2	Go to Powertrain On Board Diagnostic (OBD) System Check
2	Turn the ignition ON leaving the engine off. Install a scan tool. Engine coolant is between the specified value. Does the O2S 1 voltage remain below the specified value?	90--95°C	Go to Step 4	Go to Step 3
3	Review the Freeze Frame data. Make note of the parameters. Operate the vehicle within the Freeze Frame conditions and conditions for setting the DTC as noted. Does the O2S 1 voltage stay below the specified value?	43 mV	Go to Step 4	Go to Step 7
4	Turn the ignition ON leaving the engine off. Disconnect the O2S 1 electrical connector. Does the scan tool indicate the O2S 1 voltage within the specified value?	407-509 mV	Go to Step 7	Go to Step 5
5	Check the O2S 1 signal circuit for a short to ground. Repair as necessary. Refer to Wiring Repairs in Engine Electrical. Was a repair made?	--	Go to Step 7	Go to Step 6
6	Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete?	--	Go to Step 7	--
7	Using the scan tool, clear the DTCs. Start the Engine. Allow the engine to idle until the engine reaches the specified temperature. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text. Does the scan tool indicate that this diagnostic ran and passed?	90°-95° C	Go to Step 8	Go to Step 2
8	Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed?	--	Go to the Applicable DTC Table	System OK