Open or Short in Heated Oxygen HO Sensor Circuit DTCs P and P or P and P

During active air-fuel ratio control, the ECM calculates the Oxygen Storage Capacity (OSC)* of the Three-Way Catalytic Converter (TWC) by forcibly regulating the air-fuel ratio to become rich or lean. If the HO2 sensor has an open or short, or the voltage output of the sensor noticeably decreases, the OSC indicates an extraordinarily high value. Even if the ECM attempts to continue regulating the air-fuel ratio to become rich or lean, the HO2 sensor output does not change.

While performing active air-fuel ratio control, when the target air-fuel ratio is rich and the HO2 sensor voltage output is 0.21 V or less (lean), the ECM interprets this as an abnormally low sensor output voltage and sets DTC P0137 or P0157. When the target air-fuel ratio is lean and the voltage output is 0.59 V or more (rich) during active air-fuel ratio control, the ECM determines that the sensor voltage output is abnormally high, and sets DTC P0138 or P0158. HINT:

DTC P0138 or P0158 is also set if the HO2 sensor voltage output is more than 1.2 V for 10 seconds or more.

*: The TWC has the capability to store oxygen. The OSC and the emission purification capacity of the TWC are mutually related. The ECM determines whether the catalyst has deteriorated, based on the calculated OSC value (See page ES-203).

HO2 SENSOR CIRCUIT LOW VOLTAGE (P0137 and P0157: OPEN)

15 to 20 seconds

Active air fuel ratio control

Target air fuel ratio

HO2 sensor voltage

Stoichiometric Air Fuel Level

15 to 20 seconds

Stoichiometric Air Fuel Level

Operation

Abnormal n in n

Normal^

i__1 / L.J

^Normal

Rich r\ r ' i ! 1 !

V J w

Abnormal

HO2 SENSOR CIRCUIT HIGH VOLTAGE (P01S8 and P0158: SHORT)

Operation

Active air fuel ratio control

Target air fuel ratio

HO2 sensor voltage

Stoichiometric Air Fuel Level

Abnormal

Operation

Stoichiometric Air Fuel Level

Abnormal

High or Low Impedance of Heated Oxygen (HO2) Sensor (DTCs P0136 and P0156 or P0137 and P0157)

During normal air-fuel ratio feedback control, there are small variations in the exhaust gas oxygen concentration. In order to continuously monitor the slight variation of the HO2 sensor signal while the engine is running, the impedance* of the sensor is measured by the ECM. The ECM determines that there is a malfunction in the sensor when the measured impedance deviates from the standard range. *: The effective resistance in an alternating current electrical circuit. HINT:

• The impedance cannot be measured using an ohmmeter.

• DTCs P0136 and P0156 indicate the deterioration of the HO2 sensor. The ECM sets the DTCs by calculating the impedance of the sensor when the typical enabling conditions are satisfied (2 driving cycle).

• DTCs P0137 and P0157 indicate an open or short circuit in the HO2 sensor (2 driving cycle). The ECM sets the DTCs when the impedance of the sensor exceeds the threshold 15 kQ.

MONITOR STRATEGY

Related DTCs

P0136 P0136 P0137 P0137 P0138 P0138 P0156 P0156 P0157 P0157 P0158 P0158

Heated oxygen sensor output voltage (Output voltage) (bank 1)

Heated oxygen sensor impedance (Low) (bank 1)

Heated oxygen sensor output voltage (Low voltage) (bank 1)

Heated oxygen sensor impedance (High) (bank 1)

Heated oxygen sensor output voltage (High voltage) (bank 1)

Heated oxygen sensor output voltage (Extremely high) (bank 1)

Heated oxygen sensor output voltage (Output voltage) (bank 2)

Heated oxygen sensor impedance (Low) (bank 2)

Heated oxygen sensor output voltage (Low voltage) (bank 2)

Heated oxygen sensor impedance (High) (bank 2)

Heated oxygen sensor output voltage (High voltage) (bank 2)

Heated oxygen sensor impedance (Extremely high) (bank 2)

Required Sensors/Components (Main)

Heated oxygen sensor

Required Sensors/Components (Related)

Crankshaft position sensor, engine coolant temperature sensor, mass air flow meter and throttle position sensor

Frequency of Operation

Once per driving cycle: Active air-fuel ratio control detection Continuous: Others

Duration

20 seconds: Heated oxygen sensor output (Output voltage, High voltage, Low voltage)

30 seconds: Heated oxygen sensor impedance (Low) 90 seconds: Heated oxygen sensor impedance (High) 10 seconds: Heated oxygen sensor voltage (Extremely high)

MIL Operation

2 driving cycles

Sequence of Operation

None

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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    How to fix p0158 02 toyota tacoma?
    1 year ago

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