P0135,P0141,P0155,P0161 O2 Sensor Heater Performance

P0135,P0141,P0155,P0161 O2 Sensor Heater Performance - This allows the system to enter Cloose Loop quickly and meet the OBDII requirements for continuous monitoring and to deliver accurate readings. This is accomplished by the PCM sending a Pulse Widht Modulated (PWM) current to the O2 Sensor's heater element.

The PWM duty cycle is calculated, in response to the temperature measurements. The PCM uses the collected information to continually adjust the PWM to archive a desired steady state temperature target.

The heater temperature is obtained by measuring the heater resistance and calculating the heater temperature using the resistance versus temperature characteristic.
In order to measure the heater temperature, the transistor that controls the heater is momentarily disabled and current is passed through a precision sense resistor connected is series with the heater element.
The voltage drop across the sense resistor provides the relationship to current which equates to a temperature value. Once the temperature is acquired, the sense current is turned off and normal operation is restored.
The actual heater temperature is monitored continuously and the heating rate is adjusted to prevent damaging the heating element.

When monitored:

• Battery voltage between 11.0 and 15.75 volts.
• Ambient Air Temperature or coolant temperature above 7°C (44.6°F) at engine start up.
• Heater duty cycle greater than 0%.

Set conditions:

The Powertrain Control Module (PCM) detects  a difference of 125°C (257°F) between the target and actual temperature in the O2 Sensor Heater element. The heater temperature is obtained by measuring the heater resistance and calculating the heater temperature.Default action the MIL light will illuminate.

Possible causes:

• O2 sensor heater control circuit open/high resistance.
• O2 sensor heater ground circuit open/high resistance.
• O2 sensor.
• Powertrain Control Module (PCM).

Diagnose P0135,P0141,P0155,P0161 O2 Sensor Heater Performance

Step 1. O2 sensor heater operation

Turn the ignition off. Wait a minimum of eight minutes to allow the O2 sensor to cool down before continuing the test. Allow the O2 sensor voltage to stabilize between 4.6 and 5.0 volts. Turn the ignition on, with the scan tool, actuate the O2 sensor heater test. With the scan tool, monitor O2 sensor voltage for at least two minutes.

Does the voltage stay above 4.5 volts?

Yes, go to step 2.

No, perform the PCM intermittent condition.

Step 2. Check the O2 sensor heater element

Turn the ignition off. Allow the O2 sensor to cool down to room temperature. Disconnect the O2 sensor harness connector. Measure the resistance of the O2 sensor heater element across the O2 sensor, between the O2 heater control terminal and heater ground terminal. O2 sensor heater element resistance values should be measured at 21.1°C (70°F). The resistance value will vary with different temperature values.

Is the resistance of the O2 sensor heater element between 2.0 and 30.0 Ohms?

Yes, go to step 3.

No, verify that there is good pin to terminal contact in the sensor and Powertrain Control Module (PCM) Connectors. If no problems are found, replace the O2 sensor.

Step 3. Check the O2 sensor heater control circuit for an open/high resistance

Turn the ignition off. Disconnect the PCM harness connector, measure the resistance of the O2 sensor heater control circuit between the O2 sensor harness connector and the PCM harness connector.

Is the resistance below 0.5 Ohms?

Yes, go to step 4.

No, repair the O2 sensor heater control circuit for an open or high resistance.

Step 4. Check the O2 sensor heater ground circuit for an open/high resistance

Measure the resistance between ground and the O2 sensor heater ground circuit at the O2 sensor harness connector.

Is the resistance below 0.5 Ohms?

Yes, go to step 5.

No, repair the O2 sensor heater ground circuit for an open or high resistance.

Step 5. Check related PCM and component connections

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