P0155

DTC P0155

CIRCUIT DESCRIPTION
Heating elements inside the heated oxygen sensor (HO2S) minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. A low side driver within the powertrain control module (PCM) is pulse width controlled to provide current to the heater elements. During warm-up the PCM will pulse the heaters ON-OFF to prevent thermal shock to the sensor components from moisture in the exhaust system. The PCM will not allow continuous HO2S heating until calibrated limits of time, temperature, and intake airflow have been reached. The PCM continuously monitors the HO2S heater current draw and operating state by briefly turning OFF the heater low side driver at regular intervals. The PCM calculates the HO2S heater element resistance based on the actual heater current. If the PCM detects that the HO2S heater element resistance is too high, this DTC will set.

Each HO2S heater has the following circuits:
- HO2S heater ignition 1 voltage
- HO2S heater low control

DTC DESCRIPTOR
This diagnostic procedure supports the following DTCs.
- DTC P0135 HO2S Heater Performance Bank 1 Sensor 1
- DTC P0155 HO2S Heater Performance Bank 2 Sensor 1

CONDITIONS FOR RUNNING THE DTC
- DTCs P0030, P0036, P0050, P0056, P0117, P0118, P2414, and P2415 are not set.
- The engine is operating for more than 90 seconds.
- The ignition 1 voltage is between 10.5-16 volts.
- The engine coolant temperature (ECT) is more than -20°C (-4°F).
- The system is not in fuel cut-off mode for at least 15 seconds.
- DTCs P0135 and P0155 run continuously once the above conditions are met.

CONDITIONS FOR SETTING THE DTC
- The calculated internal resistance of the HO2S is more than 110 ohms for more than 90 seconds after an engine start.OR The calculated internal resistance of the HO2S is more than 110 ohms for more than 15 seconds.
- The A/F sensor heater internal output voltage is 0.76 V or more.
- The A/F sensor heater internal output voltage is 0.24 V or less.

ACTION TAKEN WHEN THE DTC SETS
- The PCM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or 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
- Use the J-35616 Connector Test Adapter Kit for any test that requires probing the PCM harness connector or a component harness connector.
- The Loop Status for the respective bank will default to Open when the DTC is current.
- The wide band sensors do not toggle or switch like a switching HO2S. The HO2S signals will be relatively stable for an idling engine.
- For an intermittent condition, refer to Intermittent Conditions. Intermittent Conditions




- The table illustrates the typical voltages for the HO2S circuits.

TEST DESCRIPTION

Steps 1-9:

Steps 10-21:

Step 22:

The numbers below refer to the step numbers on the diagnostic table.
4. This step tests for high resistance in the ignition 1 voltage circuit of the HO2S. If the DMM does not display near battery voltage, repair the high resistance in the ignition 1 voltage circuit.
5. This step tests the HO2S heater control circuit for a high resistance. 6 amps threw the DMM is normal when the HO2S heater control circuit is commanded ON with a scan tool. A high resistance in the circuit will cause the amperage to be less than 1 amp. Test the HO2S heater control circuit for a high resistance if the DMM displays a reading of less than 1 amp.
9. This step tests the HO2S input pump current circuit for a wire to wire short to the reference voltage circuit or a condition internal to the PCM. If the resistance measured between the circuits is more than 110,000 ohms, the PCM and the circuits are OK.
10. This step isolates the condition. Test for a wire to wire short between the HO2S input pump current and reference voltage circuits, if any continuity exists between the circuits.
15. Inspect the HO2S connector for water intrusion, corrosion, and bent or damaged terminals.
16. Inspect the PCM connectors for water intrusion, corrosion, and bent or damaged terminals.