P0134
Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Sensor 1:
Heated Oxygen Sensor (HO2S) Circuit Sensor 1:
Circuit Description
The Heated Oxygen Sensor (HO2S) produces a voltage that varies between 100mV and 9OOmV under normal operating conditions. The Powertrain Control Module (PCM) monitors this voltage and determines if the exhaust is lean or rich. If the voltage input at the PCM is about 100mV the exhaust is lean, and if the voltage input is about 9OOmV the exhaust is rich. The PCM constantly monitors the HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary. If the HO2S 1 voltage remains at or near the 450mV for an extended period of time, DTC P0134 will be set.
Conditions for Running the DTC
^ Barometric Pressure greater than 75 kPa.
^ Intake air temperature is between -10°C (14°F) and 50°C (122°F).
^ Fuel tank level greater than 25%.
Conditions for Setting the DTC
^ HO2S 1 voltage remains lower than or at 3OOmV for 10 seconds at minimum.
^ HO2S 1 voltage remains higher than or at 6OOmV for 10 seconds at minimum.
Action Taken When the DTC Sets
^ The Malfunction indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.
^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.
Conditions for Clearing the MIL/DTC
^ The MIL will turn "OFF" after three consecutively passing cycles without a fault present.
^ A History DTC will clear after 40 consecutive warm-up cycles without a fault.
^ DTC(s) can be cleared by using a scan tool or by disconnecting the PCM battery feed.
Diagnostic Aids
Check the following conditions:
^ If DTC's other than Fuel Trim (P0171, P0172), Misfire (P0300 to P0303), Exhaust Gas Recirculation (EGR) (P0400) and HO2S 1 (P0131 to P0134) are set, diagnose those DTC's first.
^ Vacuum leaks. Check for disconnected or damaged vacuum hoses and for vacuum leaks at the intake manifold, throttle body, EGR system, and crankcase ventilation system.
^ Exhaust leaks. Check for exhaust leaks near the HO2S.
^ Fuel Pressure. The system will go rich or lean if pressure is too high or low. The PCM can compensate for some increase. However, if fuel pressure is too high or low, a DTC may be set. Refer to "Fuel System Diagnosis".
^ Check the Evaporative Emissions (EVAP) System Canister for Fuel Saturation. If full of fuel, check canister control and hoses. Refer to "Evaporative Emission (EVAP) Control System."
^ Check for a leaking fuel pressure regulator diaphragm by checking vacuum line to regulator for the presence of fuel.
^ Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks. Improperly formed or damaged terminals, and poor terminal to wire connection.
^ Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the HO2S 1 display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the HO2S 1 display will indicate the location of the fault.
^ Follow DTC P0171 or P0172 for fuel system checks.
If DTC P0134 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.
If any wiring repairs need to be made, Refer to Repair Procedures in Diagrams.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The Powertrain OBD system check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
3. Determines if fault is present, vehicle must be at operating temperature.
4. Review Freeze Frame data to determine when the DTC set. Always record this information.
5. Checks for an open in the HO2S 1 ground circuit.
6. Checks for an open or short in the HO2S 1 signal circuit.