Circuit Description
The heated oxygen sensor (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 engine control module (ECM). The ECM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The ECM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the ECM will pulse the heater OFF for a duration of 5 seconds. When the heater is in the OFF state, the ECM will pulse the heater ON for a duration of 5 seconds. The ECM monitors the heater current with the engine running. The ECM also calculates the heater resistance on a cold start. Both diagnostics will only run once per ignition cycle. If the ECM detects that the heater current or the heater calculated resistance is not within the expected range, the following DTCs will set:
| • | DTC P0135 HO2S Bank 1 Sensor 1 |
| • | DTC P0141 HO2S Bank 1 Sensor 2 |
| • | DTC P0155 HO2S Bank 2 Sensor 1 |
| • | DTC P0161 HO2S Bank 2 Sensor 2 |
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | 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 |
Conditions for Running the DTC
| • | DTCs P0053, P0054, P0059, P0060, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0442, P0443, P0446, P0449, P0455, P0496, P1258, P1516, P2101, P2135, P2176 are not set. |
| • | The Engine Coolant Temperature (ECT) Sensor parameter is more than 50°C (122°F). |
| • | The Ignition 1 Signal parameter is between 10-18 volts. |
| • | The Mass Air Flow (MAF) Sensor parameter is between 3-40 g/s. |
| • | The Engine Speed parameter is between 500-3,000 RPM. |
| • | The Engine Run Time parameter is more than 300 seconds. |
| • | The above conditions are met for one second. |
| • | This diagnostic runs one time per ignition drive cycle when the above conditions are met. |
Conditions for Setting the DTC
| • | DTCs P0135 or P0155 |
| - | The ECM detects that the affected HO2S Heater Current parameter is more than 3.125 amps or less than 0.25 amps. |
| - | The above condition is met for 5 seconds. |
| • | DTCs P0141 or P0161 |
| - | The ECM detects that the affected HO2S Heater Current parameter is more than 1.625 amps or less than 0.25 amps. |
| - | The above condition is met for 5 seconds. |
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 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 | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||
2 | Is DTC P0135 or P0155 set? | -- | Go to Step 4 | Go to Step 3 | ||||
3 |
Is the HO2S Heater Current parameter within the specified range? | 0.25-1.625 A | Go to Step 5 | Go to Step 6 | ||||
4 |
Is the HO2S Heater Current parameter within the specified range? | 0.25-3.125 A | Go to Step 5 | Go to Step 6 | ||||
5 |
Did the DTC fail this ignition? | -- | Go to Step 6 | Go to Testing for Intermittent Conditions and Poor Connections | ||||
6 |
Is the fuse open? | -- | Go to Step 7 | Go to Step 8 | ||||
7 | Test the ignition 1 voltage circuit for a short to ground. Refer to the following 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 1 connector for a short to ground. Refer to Circuit Testing . Is the sensor shorted to ground? | -- | Go to Step 20 | Go to Testing for Intermittent Conditions and Poor Connections | ||||
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:
Refer to Circuit Testing . Is the resistance of either circuit more than the specified value? | 3ohms | Go to Step 18 | Go to Step 16 | ||||
13 | Test the HO2S heater low control circuit for a short to ground. Refer to the following 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 the following 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 the following 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 the following 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 engine control module (ECM). Refer to the following 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 and Heated Oxygen Sensor Wiring Repairs . 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 and Heated Oxygen Sensor Wiring Repairs . | -- | Go to Step 22 | -- | ||||
20 | Replace the affected HO2S. Refer to the following procedures: Did you complete the replacement? | -- | Go to Step 22 | -- | ||||
21 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 22 | -- | ||||
22 | Were you sent to this diagnostic from DTC P0134 or P0154? | -- | Go to DTC P0134 or P0154 | Go to Step 23 | ||||
23 | Were you sent to this diagnostic from DTC P0140 or P0160? | -- | Go to DTC P0140 or P0160 | Go to Step 24 | ||||
24 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 25 | ||||
25 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||
