P0131

(P0131) 02 SENSOR 1/1 CIRCUIT LOW

Monitored and Set Condition
^ When Monitored: With the engine running between 1000 and 2000 RPM, engine load between 15% to 50%, closed loop mode, the three way catalytic converter temperature is greater than 380°C (76°F), and the 02 sensor heater must be ON for at least 220 seconds to enable the signal inactive portion of the test.
^ Set Condition: The high limit: 02 Sensor voltage is greater than 1.5 volts for approximately 5 seconds. The low limit: 02 Sensor voltage is less than 0.15 volt for approximately 5 seconds. Signal stays at center: The 02 Sensor voltage stays between 0.4 and 0.6 volt for more than approximately 15 seconds after the 02 Sensor heater has been ON for at least 220 seconds.

POSSIBLE CAUSES
- 02 SENSOR SIGNAL CIRCUIT OPEN
- 02 SENSOR SIGNAL CIRCUIT SHORT TO GROUND
- 02 SENSOR SIGNAL CIRCUIT SHORT TO VOLTAGE
- SENSOR GROUND CIRCUIT OPEN
- ENGINE EXHAUST LEAK
- 02 SENSOR
- POWERTRAIN CONTROL MODULE

Diagnostic Test
1. PRE-DIAGNOSTIC CHECK OUT

Note: Always perform diagnostics with a fully charged battery.

Note: Check connectors - Clean/repair as necessary. Poor pin to terminal connections can set DTCs.

Note: Check for applicable TSBs related to the problem. Turn the ignition on. With the DRBIII, read PCM DTCs. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors. Repair as necessary. Perform this procedure prior to symptom diagnosis.

Continue
Go To 2

2. MONITOR THE 02 SENSOR VOLTAGE

Turn the ignition on. With the DRBIII, monitor the 02 Sensor Signal voltage of the affected Sensor.
Is the 02 Sensor voltage above 1.4 volts or below 0.15 volt?
Yes >> If the value is greater than 1.4 volts, Go To 4
If the value is less than 0.15 volt, Go To 6
No >> Go To 3

3. 02 SENSOR VOLTAGE

Start the engine. Operate the engine above 1200 RPM for 3 minutes and 40 seconds. With the DRBIII, monitor the 02 Sensor Signal voltage.
Does the 02 Sensor voltage stay between 0.4 and 0.6 volt?
Yes >> Go To 12
No >> Go To 8

4. DISCONNECT THE 02 SENSOR

With the ignition on. With the DRBIII, monitor the 02 Sensor Signal voltage.
Is the 02 Sensor voltage above 2.0 volts?
Yes >> Repair the 02 Sensor Signal circuit for a short to voltage. Perform POWERTRAIN VERIFICATION TEST - VER 2 Powertrain Verification Test - Ver 2.
No >> Replace and program the Powertrain Control Module. Perform POWERTRAIN VERIFICATION TEST - VER 2 Powertrain Verification Test - Ver 2.

6. DISCONNECT THE 02 SENSOR

Turn the ignition off. Disconnect the 02 Sensor harness connector of the affected sensor.

Note: Check connectors - Clean/repair as necessary.

Turn the ignition on. With the DRBIII, monitor the 02 Sensor Signal voltage.
Is the 02 Sensor voltage above 0.15 volt?
Yes >>

Note: Determine the cause of any contamination before replacing the sensor. Inspect for the following before replacing the 02 Sensor.
^ Fuel contamination.
^ Engine oil or coolant consumption.
^ Use of improper RTV sealant. Replace the 02 Sensor if none of the above conditions are present. Perform POWERTRAIN VERIFICATION TEST - VER 2 Powertrain Verification Test - Ver 2.
No >> Go To 7

7. 02 SENSOR SIGNAL CIRCUIT SHORT TO GROUND

Turn the ignition off. Disconnect the PCM harness connectors.

Note: Check connectors - Clean/repair as necessary.

Measure the resistance between ground or any ground circuit in the PCM harness connector and the 02 Sensor Signal circuit.
Is the resistance above 100 kohms for all measurements?
Yes >> Replace and program the Powertrain Control Module. Perform POWERTRAIN VERIFICATION TEST - VER 2 Powertrain Verification Test - Ver 2.
No >> Repair the 02 Sensor Signal circuit for a short to ground or any ground circuit in the PCM harness connector. Perform POWERTRAIN VERIFICATION TEST - VER 2 Powertrain Verification Test - Ver 2.

8. 02 SENSOR SYSTEM INSPECTION
Turn the ignition off. Inspect for the following conditions.
Exhaust leak. Incorrectly installed 02 Sensor. Damaged wiring.
Were any of the above conditions found?
Yes >> Repair as necessary Perform POWERTRAIN VERIFICATION TEST - VER 2 Powertrain Verification Test - Ver 2.
No >> Go To 9

9. JUMPER THE 02 SENSOR

With the ignition off. Disconnect the 02 Sensor harness connector of the affected 02 Sensor.

Note: Check connectors - Clean/repair as necessary. Turn the ignition on. Connect a jumper wire between ground and the 02 Sensor Signal circuit. With the DRBIII, monitor the 02 Sensor Signal voltage.

Does the 02 Sensor voltage stay between 0.4 and 0.6 volt?
Yes >> Go To 10
No >> Go To 11

10. 02 SENSOR SIGNAL CIRCUIT OPEN

Turn the ignition off. Disconnect the PCM harness connectors.

Note: Check connectors - Clean/repair as necessary.

Measure the resistance of the 02 Sensor Signal circuit from the 02 Sensor harness connector to the PCM harness connector.
Is the resistance below 5.0 ohms?
Yes >> Replace and program the Powertrain Control Module. Perform POWERTRAIN VERIFICATION TEST - VER 2 Powertrain Verification Test - Ver 2.
No >> Repair the 02 Sensor Signal circuit for an open. Perform POWERTRAIN VERIFICATION TEST - VER 2 Powertrain Verification Test - Ver 2.

11. SENSOR GROUND CIRCUIT OPEN

Turn the ignition off. Disconnect the PCM harness connectors.

Note: Check connectors - Clean/repair as necessary.

Measure the resistance of the Sensor Ground circuit from the 02 Sensor harness connector to the PCM harness connector.
Is the resistance below 5.0 ohms?
Yes >>

Note: Determine the cause of any contamination before replacing the sensor. Inspect for the following before replacing the 02 Sensor.
^ Fuel contamination.
^ Engine oil or coolant consumption.
^ Use of improper RTV sealant.

Replace the Oxygen Sensor if none of the above conditions are present. Perform POWERTRAIN VERIFICATION TEST - VER 2 Powertrain Verification Test - Ver 2.
No >> Repair the Sensor Ground circuit for an open. Perform POWERTRAIN VERIFICATION TEST - VER 2 Powertrain Verification Test - Ver 2.

12. INTERMITTENT WIRING AND CONNECTORS
The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition.

Note: Check connectors - Clean/repair as necessary. Poor pin to terminal connections can set DTCs. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors specific to this DTC. Wiggle the wires while checking for shorts and open circuits.

Note: Check for any Technical Service Bulletins that may apply.

Were there any problems found?
Yes >> Repair as necessary. Perform POWERTRAIN VERIFICATION TEST - VER 2 Powertrain Verification Test - Ver 2.
No >> The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition.