P0134
DTC P0134 HEATED OXYGEN SENSOR CIRCUIT NO ACTIVITY DETECTED (BANK 1 SENSOR 1)HINT: Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.
CIRCUIT DESCRIPTION
DTC Detecting Conditions:
The front Heated Oxygen (HO2) sensor monitors the oxygen concentration in the exhaust gas. For optimum TWC operation, the air-fuel mixture must be maintained as close as possible to the stoichiometric ratio. The HO2 sensor output voltage changes dramatically in the vicinity of the stoichiometric ratio. By making adjustments in accordance to these signal voltages, the ECM adjusts the fuel injection time so that the air-fuel ratio remains close to stoichiometric levels.
If the oxygen concentration in the exhaust gas increases, the air-fuel ratio is lean and the HO2 sensor output voltage to the ECM drops below 0.45 V. If the oxygen concentration in the exhaust gas decreases, the air-fuel ratio is rich and the HO2 sensor output voltage to the ECM increases to above 0.45 V.
HINT: If this DTC is set, check the output voltage of the HO2 sensor (bank 1 sensor 1) by selecting the following menu items on a hand-held tester: DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL. If using an OBD II scan tool, refer to the instruction manual.
MONITOR DESCRIPTION
Monitor Strategy:
Typical Enabling Condition:
Typical Malfunction Thresholds:
Component Operating Range:
The ECM uses the front HO2 sensor to optimize the air-fuel ratio with closed-loop fuel control. This control helps to decrease exhaust emissions by keeping the conditions optimum for the TWC to work at maximum efficiency. The front HO2 sensor detects the oxygen level in the exhaust gas, and provides the ECM with feedback to allow it to control the air-fuel ratio accurately.
The front HO2 sensor voltage output ranges from 0 V to 1 V. When the sensor signal voltage is less than 0.45 V, the air-fuel ratio is lean. Conversely, when it is more than 0.45 V, the air-fuel ratio is rich. If the front HO2 sensor does not indicate rich at all despite the closed-loop fuel control conditions being met for a certain period of time, the ECM determines that closed-loop fuel control is malfunctioning. The ECM illuminates the MIL and sets the DTC.
CONFIRMATION DRIVING PATTERN
HINT: This confirmation driving pattern is used in step 12 of the following diagnostic troubleshooting procedure.
a. Connect a hand-held tester or OBD II scan tool to the DLC3.
b. Turn the ignition switch to ON.
c. Turn the tester or scan tool ON.
d. Clear DTCs.
e. Start the engine.
f. Allow the engine to idle until the engine coolant temperature reaches 40°C (104°F).
g. Drive the vehicle at a speed of more than 38 mph (60 km/h) for 3 minutes or more.
NOTE: If the conditions in this test are not strictly followed, malfunctions may not be detected.
Wiring Diagram:
Step 1 - 3:
Step 4 - 5:
Step 6:
Step 7 - 12:
Step 13 - 14:
INSPECTION PROCEDURE
HINT: Hand-held tester only:
Malfunctioning areas can be identified by performing the A/F CONTROL function provided in the ACTIVE TEST. The A/F CONTROL function can help to determine whether the Heated Oxygen (HO2) sensors and other potential trouble areas are malfunctioning.
The following instructions describe how to conduct the A/F CONTROL operation using a hand-held tester.
1. Connect a hand-held tester to the DLC3.
2. Start the engine and turn the tester ON.
3. Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
4. On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
5. Perform the A/F CONTROL operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
6. Monitor the voltage output of the HO2 sensors (O2S B1S1 and OS2 B1S2) displayed on the tester.
HINT:
- The A/F CONTROL operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.
- Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
NOTE: The front HO2 sensor has an output delay of a few seconds and the rear HO2 sensor has a maximum output delay of approximately 20 seconds.
- Following A/F CONTROL procedure enables technicians to check and graph the voltage outputs of both the front and rear HO2 sensors.
- To display the graph, select the following menu items on the tester: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST/ A/F CONTROL / USER DATA / AFS B1S2 and OS2 B1B2, and press the YES button and then the ENTER button followed by the F4 button.
NOTE: If the vehicle is short of fuel, the air-fuel ratio becomes lean and HO2 sensor DTCs are recorded, and the ECM illuminates the MIL.
HINT:
- If other DTCs relating to different systems that have terminal E2 as the ground terminal are output simultaneously, terminal E2 may have an open circuit.
- Read freeze frame data using a hand-held tester or OBD II scan tool. Freeze frame data record the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data, from the time the malfunction occurred.
- A high HO2 sensor (sensor 1) voltage (0.55 V or more) could be caused by a rich air fuel mixture. Check for conditions that would cause the engine to run rich.
- A low HO2 sensor (sensor 1) voltage (0.4 V or less) could be caused by a lean air fuel mixture. Check for conditions that would cause the engine to run lean.
CHECK FOR INTERMITTENT PROBLEMS
HINT: Hand-held tester only:
Inspect the vehicle's ECM using check mode. Intermittent problems are easier to detect with a hand-held tester when the ECM is in check mode. In check mode, the ECM uses 1 trip detection logic, which is more sensitive to malfunctions than normal mode (default), which uses 2 trip detection logic.
a. Clear DTC.
b. Switch the ECM from normal mode to check mode using a hand-held tester.
c. Perform a simulation test.
d. Check and wiggle the harness(es), connector(s) and terminal(s).