Diagnostic Instructions

DTC Descriptors

DTC P0135: HO2S Heater Performance Bank 1 Sensor 1

DTC P0141: HO2S Heater Performance Bank 1 Sensor 2

DTC P0155: HO2S Heater Performance Bank 2 Sensor 1

DTC P0161: HO2S Heater Performance Bank 2 Sensor 2

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Ignition Voltage Supply - HO2S 1	P0030, P0031, P0050, P0051	P0010, P0013, P0023, P0030, P0031, P0050, P0051, P0134, P0135, P0154, P0155, P0458, P2088	--	--
Ignition Voltage Supply - HO2S 2	P0036, P0037, P0056, P0057	P0036, P0037, P0056, P0057, P0140, P0160, P0645, P0646, P0691, P0693	--	--
HO2S Bank 1 Sensor 1 Heater Control	P0031	P0030, P0134	P0032	P0135
HO2S Bank 1 Sensor 2 Heater Control	P0037	P0036, P0140	P0038	P0141
HO2S Bank 2 Sensor 1 Heater Control	P0051	P0050, P0154	P0052	P0155
HO2S Bank 2 Sensor 2 Heater Control	P0057	P0056, P0160	P0058	P0161

Circuit Description

The heated oxygen sensor (HO2S) heater reduces the time required for the oxygen sensor to reach operating temperature and maintains the operating temperature during extended idle periods. When the ignition is turned to the ON position, ignition voltage is supplied directly to the sensor heater. The engine control module (ECM) controls the heater operation by first modulating the control circuit to ground when the sensors are cold. This prevents the possibility of thermal shock to the sensor, from condensation build-up on the sensor, by controlling the sensor's rate of heating. After a predetermined amount of time, the ECM commands the heaters ON continuously. Once the sensor reaches operating temperature, the ECM may modulate the heater control circuit to ground to maintain a desired temperature. The ECM controls the heater by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled up to voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage.

Conditions for Running the DTC

P0135 or P0155

P0141 or P0161

Conditions for Setting the DTC

P0135 or P0155

The ECM detects that the internal resistance of the HO2S 1 heater is not within the expected range for greater than 12 seconds.

P0141 or P0161

The ECM detects that the internal resistance of the HO2S 2 heater is not within the expected range for greater than 6 seconds.

Action Taken When the DTC Sets

DTCs P0135, P0141, P0155, and P0161 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0135, P0141, P0155, and P0161 are Type B DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Note: It may take up to 8 minutes for the DTC to set.

1. With the engine at normal operating temperature, operate the engine above 1,200 RPM for 2 minutes and then allow the engine to idle. DTCs P0135, P0141, P0155, or P0161 should not set.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the appropriate HO2S.
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C and ground.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all the components connected to the ignition circuit and replace as necessary.

3. Ignition OFF, connect a test lamp between the heater control circuit terminal D and B+. The test light should not illuminate.

⇒	If test lamp illuminates, test the heater control circuit for a short to ground. If the circuit/connections test normal, replace the ECM.

4. Idle the engine, and verify the test lamp illuminates or flashes with bright intensity.

⇒	If the test lamp is always OFF, test the control circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.

Note: The control circuit for the HO2S heater is pulled-up to voltage within the ECM, 2.0-3.0 volts on the control circuit is normal.

5. Ignition ON, test for 2.0-3.0 volts between the control circuit terminal D and ground.

⇒	If not within the specified range, test the control circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.

6. If all circuits/connections test normal, test or replace the HO2S.

Component Testing

1. Ignition OFF, disconnect the harness connector of the appropriate HO2S.
2. Test the HO2S heater element for 3-35 Ω.

⇒	If not within the specified range, replace the HO2S.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.