P0139

DTC P0139

CIRCUIT DESCRIPTION
The secondary heated oxygen sensor (HO2S) measures the oxygen content of the exhaust downstream of the three-way catalyst (TWC), so that the TWC efficiency is optimized. The powertrain control module (PCM) supplies a voltage near 450 mV between the HO2S high signal circuit and the low reference circuit. The HO2S varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.

The PCM monitors and stores the HO2S voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time that the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range.

The PCM monitors the HO2S voltage and detects if the voltage goes out of the bias range. If the PCM does not detect the voltage went out of the bias range, this DTC sets.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC P0139 HO2S Slow Response Bank 1 Sensor 2
- DTC P0159 HO2S Slow Response Bank 2 Sensor 2

CONDITIONS FOR RUNNING THE DTC
- DTCs P0030, P0107, P0108, P0112, P0113, P0117, P0118, P0133, P0135, P0137, P0138, P0141, P0153, P0155, P0157, P0158, P0161, P0171, P0172, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0335, P0401, P0404, P0443, P0496, P1128, P1129, P2270, P2271, P2272, P2273, P2413, and P2414, are not set.
- The engine has been running for at least 2 minutes.
- The engine speed is between 1,000-2,400 RPM.
- The engine coolant (ECT) temperature is at least 69°C (156°F).
- The intake air (IAT) temperature is at least -18°C (0°F).
- The HO2S 1 same bank lambda is between 0.73-1.47.
- The vehicle speed is more than 48 km/h (30 mph)
- The engine is in closed loop.
- DTCs P0139 and P0159 run once per drive cycle when the above conditions are met.

CONDITIONS FOR SETTING THE DTC
The HO2S 2 output voltage is between 0.29-0.75 volts for 30 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS
- An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provide the supply of oxygen. Inspect the HO2S wires and connections for breaks or contamination.
- For an intermittent condition, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Steps 1-8:

Steps 9-13:

The numbers below refer to the step numbers on the diagnostic table.
2. The engine must be at the normal operating temperature before performing this test.
4. If the scan tool indicates the HO2S voltage goes below 100 mV, this indicates the HO2S circuits and the PCM are OK.
5. This step isolates the condition. Test the HO2S low reference circuit for an open or a high resistance, if the observed voltage is less than 100 mV.