P0161
DTC P0161
CIRCUIT DESCRIPTION
The heated oxygen sensor (HO2S) must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. With the engine running, ground is provided to the heater by the HO2S heater low control circuit, through a low side driver within the engine control module (ECM). The ECM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The ECM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the ECM will pulse the heater OFF for a duration of 50 ms, once per second. When the heater is in the OFF state, the ECM will pulse the heater ON for a duration of 50 milliseconds, once per second. The ECM monitors the heater current with the engine running. The ECM also calculates the heater resistance on a cold start. Both diagnostics will only run once per ignition cycle. If the ECM detects that the heater current or the heater calculated resistance is not within the expected range, the following DTCs will set:
- DTC P0135 for HO2S bank 1 sensor 1
- DTC P0141 for HO2S bank 1 sensor 2
- DTC P0155 for HO2S bank 2 sensor 1
- DTC P0161 for HO2S bank 2 sensor 2
DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC P0135 HO2S Heater Performance Bank 1 Sensor 1
- DTC P0141 HO2S Heater Performance Bank 1 Sensor 2
- DTC P0155 HO2S Heater Performance Bank 2 Sensor 1
- DTC P0161 HO2S Heater Performance Bank 2 Sensor 2
CONDITIONS FOR RUNNING THE DTC
Heater Current Test
- DTCs P0053, P0054, P0059, P0060, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0442, P0443, P0446, P0449, P0455, P0496, P1258, P1516, P2101, P2135, P2176 are not set.
- The Engine Coolant Temperature (ECT) Sensor parameter is more than 50°C (122°F).
- The Ignition 1 Signal parameter is between 10-18 volts.
- The Mass Airflow (MAF) Sensor parameter is between 3-40 g/s.
- The Engine Speed parameter is between 500-3,000 RPM.
- The Engine Run Time parameter is more than 120 seconds.
- The above conditions are met for 2 seconds.
- This diagnostic runs one time per ignition drive cycle once the above conditions are met.
Heater Resistance Test
- DTCs P0053, P0054, P0059, P0060, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0442, P0443, P0446, P0449, P0455, P0496, P1258, P1516, P2101, P2135, or P2176 are not set.
- The ignition is OFF for more than 10 hours.
- The ECT Sensor parameter is between -30 and +45°C (-22 and +113°F) at engine start-up.
- The ECT Sensor parameter minus the Intake Air Temperature (IAT) Sensor parameter is less than 8°C (14°F) at engine start-up.
- The engine is started.
- The above conditions are met for up to 100 seconds.
- This diagnostic runs one time per valid cold start once the above conditions are met.
CONDITIONS FOR SETTING THE DTC
Heater Current Test
- DTCs P0135 or P0155
- The ECM detects that the affected HO2S Heater Current parameter is more than 3.125 amps or less than 0.25 amp.
- The above condition is met for 5 seconds.
- DTCs P0141 or P0161
- The ECM detects that the affected HO2S Heater Current parameter is more than 1.375 amps or less than 0.25 amp.
- The above condition is met for 5 seconds.
Heater Resistance Test
DTCs P0135, P0141, P0155, or P0161-The powertrain control module (PCM) detects that the affected HO2S heater calculated resistance is not within an expected range at engine start-up for 1 second.
ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.
TEST
