P0135, P0141, P0155, or P0161 (W/LR4 and LM7 W/ Denso HO2S)

DTC P0135, P0141, P0155, or P0161 (W/LR4 and LM7 W/ Denso HO2S)

Circuit Description

This diagnostic applies only to vehicles built with Denso heated oxygen sensors. To identify the heated oxygen sensor refer to Oxygen Sensor Identification Component Locations.

The powertrain control module (PCM) supplies a bias voltage of approximately 450 mV on the heated oxygen sensor (HO2S) signal high and low circuits. When you turn the ignition to the ON position, battery voltage is supplied to the HO2S heater. As the heater reaches the operating temperature, the HO2S voltage responds by changing from a bias voltage range to the normal operation. Typically, as the HO2S reaches the operating temperature, the HO2S voltage goes from a bias voltage to a voltage below 300 mV. Depending on the exhaust gas content, it is possible for the HO2S voltage to go above 450 mV.

The PCM runs the heater test only on a cold start (depends on the cumulative air flow) and only once an ignition cycle. When you start the engine the PCM monitors the HO2S voltage. When the HO2S voltage goes above or below the bias range threshold, the PCM determines how much time it took. If the PCM detects that the process took too much time for the HO2S to enter into normal operating range, a DTC sets. The time the process takes the HO2S to reach operating temperature is based on the amount of air that flows into the engine.

Conditions for Running the DTC

- DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0134, P0137, P0138, P0140, P0151, P0152, P0154, P0157, P0158, P0160, P0200, P0300, P0401, P0404, P0405, P0410, P0440, P0442, P0446, P0452, P0453, P1120, P1125, P1220, P1221, P1258, P1404, P1415, P0416, P1514, P1515, P1516, P1517, or P1518 are not set.
- The HO2S voltage is between 425-475 mV at engine start-up.
- The intake air temperature (IAT) and the engine coolant temperature (ECT) are less than 50°C (122°F) and are within 8°C (14.5°F) of each other at engine start-up.
- The ignition 1 signal is between 9�18 volts.
- Intrusive tests are not in progress.
- The scan tool output controls are not active.
- The scan tool is disconnected.

Conditions for Setting the DTC

The HO2S voltage remains within 150 mV of the start-up voltage for a predetermined amount of time, based on ECT and air flow.

Action Taken When the DTC Sets

- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

Important: Never solder the HO2S wires. For proper wire and connection repairs, refer to Wiring Repairs or to Connector Repairs Diagnostic Aids.

An intermittent may be caused by any of the following conditions:

- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections Diagnostic Aids.

If a repair is necessary, then refer to Wiring Repairs or Connector Repairs Diagnostic Aids.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

2. As the heater warms the oxygen sensor to operating temperature, the HO2S will output a voltage in relation to the amount of oxygen in the exhaust. With the ignition ON and the engine OFF, the exhaust usually contains a high oxygen content. With the engine OFF, the HO2S voltage will usually decrease from the initial voltage due to the high oxygen content.
4. This step checks for proper HO2S heater ignition positive voltage and ground supply.
5. This step checks for proper PCM and signal circuit operation.