Circuit Description
Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. With the engine running, ground is provided to the heater by the HO2S heater low control circuit, through a low side driver within the powertrain control module (PCM). The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater and calculating the resistance. Based on the resistance, the PCM can predict the sensor temperature. The HO2S 1 uses pulse width modulation (PWM) to control the heater operation. The HO2S 2 simply uses ON/OFF commands to control the heater operation. For diagnosis, the PCM monitors the heater current with the engine running. the PCM also calculates the heater resistance on a cold start. Both diagnostics will only run once per ignition cycle.
If the PCM detects that the heater current or the heater calculated resistance is not within an expected range, DTC P0141 sets for HO2S 2.
Conditions for Running the DTC
Heater Current Test
| • | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0118, P0120, P0121, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0220, P0442, P0443, P0446, P0449, P0452, P0453, P0455, P0496, P1221, P1516, P2101, P2176 are not set. |
| • | The ECT Sensor parameter is more than 70°C (158°F). |
| • | The Ignition 1 Signal parameter is between 10-18 volts. |
| • | The MAF Sensor parameter is between 15-30 g/s. |
| • | The Engine Run Time parameter is more than 100 seconds. |
| • | The Engine Speed parameter is between 1,000-2,500 RPM. |
Heater Resistance Test
| • | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0118, P0120, P0121, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0220, P0442, P0443, P0446, P0449, P0452, P0453, P0455, P0496, P1221, P1516, P2101, P2176 are not set. |
| • | The ignition is OFF for more than 10 hours. |
| • | The ECT Sensor parameter is between -30 to +45°C (-22 to +113°F) at engine start-up. |
| • | The ECT Sensor parameter minus the IAT Sensor parameter is less than 140°C (252°F) at engine start-up. |
| • | The engine is running. |
Conditions for Setting the DTC
Heater Current Test
| • | The PCM detects that the HO2S 2 heater current parameter is more than 1.5 amps or less than 0.199 amps. |
| • | The above condition is met for 30 seconds. |
Heater Resistance Test
The PCM detects that the HO2S 2 heater calculated resistance is not within an expected range at engine start-up.
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. |
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||
2 |
Is the HO2S 2 heater current parameter within the specified range? | 0.199-1.5 A | Go to Step 3 | Go to Step 6 | ||||||
3 | Observe the Freeze Frame/Failure Records for this DTC. Did the DTC fail with an engine run time of less than 10 seconds? | -- | Go to Step 4 | Go to Step 5 | ||||||
4 |
Did the DTC fail this ignition? | -- | Go to Step 6 | Go to Intermittent Conditions | ||||||
5 |
Did the DTC fail this ignition? | -- | Go to Step 6 | Go to Intermittent Conditions | ||||||
6 |
Is the O2S sensor fuse open? | -- | Go to Step 7 | Go to Step 8 | ||||||
7 | Test the ignition 1 voltage circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 10 | ||||||
8 |
Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 19 | ||||||
9 |
Does the test lamp illuminate? | -- | Go to Step 13 | Go to Step 11 | ||||||
10 | Test the ignition 1 voltage circuit on the sensor side of the HO2S connector for a short to ground. Refer to Circuit Testing in Wiring Systems. Is the sensor shorted to ground? | -- | Go to Step 20 | Go to Intermittent Conditions | ||||||
11 | Start the engine, with the test lamp still connected from the previous step. Is the test lamp on steady or blinking? | -- | Go to Step 12 | Go to Step 14 | ||||||
12 | Measure the resistance of the following circuits with a DMM:
Is the resistance of either circuit more than the specified value? | 3 ohms | Go to Step 18 | Go to Step 16 | ||||||
13 | Test the HO2S heater low control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 17 | ||||||
14 | Test the HO2S heater low control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 15 | ||||||
15 | Test the HO2S heater low control circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 17 | ||||||
16 | Test for shorted terminals and for poor connections at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 20 | ||||||
17 | Test for shorted terminals and for poor connections at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 21 | ||||||
18 | Repair the circuit with high resistance. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 22 | -- | ||||||
19 | Repair the open or high resistance in the ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 22 | -- | ||||||
20 |
Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section. Replace the HO2S 2. Refer to Heated Oxygen Sensor 1 Replacement or Heated Oxygen Sensor 2 Replacement . Did you complete the replacement? | -- | Go to Step 22 | -- | ||||||
21 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 22 | -- | ||||||
22 | Were you sent to this diagnostic from DTC P0140? | -- | Go to Step 18 in DTC P0140 | Go to Step 23 | ||||||
23 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 24 | ||||||
24 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
