DTC P0137, P0138, or P0140 (Without LF1)
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DTC P0137, P0138, or P0140 (Without LF1)
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DTC P0137
HO2S Circuit Low Voltage Sensor 2
DTC P0138
HO2S Circuit High Voltage Sensor 2
DTC P0140
HO2S Circuit Insufficient Activity Sensor 2
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Diagnostic Fault Information
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Circuit
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Short to Ground
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Open/High Resistance
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Short to Voltage
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Signal Performance
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HO2S Sensor 1 Signal
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P0131
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P0134, P0135
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P0132
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P0133, P2096, P2097
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HO2S Sensor 2 Signal
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P0137
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P0140
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P0138
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P0140
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Low Reference
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-
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P0134, P0135
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-
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-
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HO2S 2
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Circuit
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Short to Ground
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Open
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Short to Voltage
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Operating Conditions:
Engine operating in closed loop.
Parameter Normal Range:
Fluctuates above and below 350-500 mV.
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Sensor Signal
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0-60 mV
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400-455 mV
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1275 mV
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Low Reference
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-
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400-455 mV
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1275 mV
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The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias voltage of about 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, closed loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.
The heating elements inside each HO2S heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.
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Conditions for Running the DTCs
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P0137
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DTC P0117 or P0118 is not set.
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The HO2S 2 is at operating temperature for greater than 90 seconds.
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The engine is operating for greater than 5 seconds.
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The ignition voltage is greater than 10 volts.
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The engine coolant temperature is less than 40°C (104°F) at start-up and the engine coolant temperature was greater than 60°C (140°F) when the ignition was turned OFF last ignition cycle.
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DTCs P0137 runs continuously once the above conditions are met.
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P0138 and P0140
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The HO2S 2 is at operating temperature for greater than 30 seconds.
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The engine is operating for greater than 1 second.
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The ignition voltage is greater than 10 volts.
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DTCs P0138 runs continuously once the above conditions are met for greater than 5 seconds.
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DTCs P0140 runs continuously once the above conditions are met for greater than 60 seconds.
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Conditions for Setting the DTC
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P0137
The ECM detects that a secondary HO2S signal voltage is less than 60 mV for greater than 1 seconds of for a cumulative of 10 seconds.
P0138
The ECM detects that the HO2S signal voltage is greater than 1,150 mV for greater than 1 seconds or for a cumulative of 10 seconds.
P0140
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The ECM detects that the HO2S 2 signal voltage is between 401-519 mV, when the calculated exhaust temperature is less than 800°C (1,472°F).
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The ECM detects that the HO2S 2 signal voltage is between 401-548 mV, when the calculated exhaust temperature is greater than 800°C (1,472°F).
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The ECM detects that the measured internal resistance of the HO2S is greater than 40,000 Ω, when the calculated exhaust temperature is greater than 450°C (802°F).
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The ECM detects any one of the above conditions for greater than 1 second or for a cumulative of 10 seconds.
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Action Taken when the DTC Sets
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DTCs P0137, P0138, and P0140 are Type B DTCs.
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Conditions for Clearing the MIL/DTC
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DTCs P0137, P0138, and P0140 are Type B DTCs.
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References
for scan tool information
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Circuit/System Verification
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1.
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Engine idling, observe the scan tool HO2S 2 voltage parameter. The reading should fluctuate above and below the range of 350-550 mV.
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2.
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Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
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1.
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Ignition OFF, disconnect the harness connector at the B52 HO2S 2.
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2.
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Ignition ON, verify that the scan tool HO2S 2 voltage parameter is between 350-500 mV.
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3.
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If less than the specified range, test the signal circuit terminal 4 for a short to ground. If the circuit/connections test normal, replace the K20 ECM.
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4.
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If greater than the specified range, test the signal circuit terminal 4 for a short to voltage. If the circuit/connections test normal, replace the K20 ECM.
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5.
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Connect a 3 A fused jumper wire between the signal circuit terminal 4 and ground. Verify the scan tool HO2S voltage parameter is less than 60 mV.
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6.
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If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit/connections test normal, replace the K20 ECM.
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7.
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Connect a 3 A fused jumper wire between the signal circuit terminal 4 and the low reference circuit terminal 3. Verify the scan tool HO2S 2 voltage parameter is less than 60 mV.
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8.
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If greater than the specified range, test the low reference circuit for an open/high resistance, or for a short to voltage. If the circuit/connections test normal, replace the K20 ECM.
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9.
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Verify the following conditions do not exist:
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Evidence of water intrusion into the electrical connector of the HO2S
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Exhaust leaks near the HO2S
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If you find any of the above conditions, repair as necessary.
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10.
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If all circuits/connections test normal, replace the B52 HO2S 2 sensor.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
