P0151
DTC P0151
CIRCUIT DESCRIPTION
The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust stream more quickly and accurately than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell, and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The engine control module (ECM) supplies a signal voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a constant signal voltage. The ECM monitors the voltage variation on the signal circuit and attempts to keep the voltage constant by increasing or decreasing the amount of current flow or reversing the direction of the current flow to the pumping cell. By measuring the direction and amount of current required to maintain the signal voltage, the ECM can determine the concentration of oxygen in the exhaust. The signal voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the system is lean, the oxygen level will be high and the lambda value will be high, or more than 1. When the system is rich, the oxygen level is low and the lambda value will be low, or less than 1. The ECM uses this information to maintain the proper air/fuel ratio. If the ECM detects an HO2S circuit that is shorted to ground, DTC P0131 will set for bank 1 sensor 1, or DTC P0151 will set for bank 2 sensor 1.
DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1
- DTC P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1
CONDITIONS FOR RUNNING THE DTC
- DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0132, P0133, P0135, P0137, P0138, P0139, P0140, P0141, P0152, P0153, P0155, P0157, P0158, P0159, P0160, P0161, P1137, P1138, P1157, P1158, P2231, P2234, P2237, P2240, P2243, P2247, P2251, P2254, P2626, P2629, P167A, P167B are not set.
- The engine is running.
- DTC P0131 or P0151 runs continuously once the above conditions are met.
CONDITIONS FOR SETTING THE DTC
The ECM detects a short to ground in one of the following HO2S circuits for more than 1 second:
- The input pump current circuit
- The output pump current circuit
- The reference voltage circuit
- The low reference circuit
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 malfunction indicator lamp (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
