Circuit Description
Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.
The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.
If the PCM detects that the HO2S 1 heater low control circuit current level is not within the calibrated range, DTC P0135 will set.
Each HO2S 1 has the following circuits:
| • | An HO2S 1 high signal circuit |
| • | An HO2S 1 low signal circuit |
| • | An HO2S 1 heater ignition voltage circuit |
| • | An HO2S 1 heater low control circuit |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0135 HO2S Heater Performance Bank 1 Sensor 1
Conditions for Running the DTC
| • | DTCs P0030, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0201, P0202, P0203, P0204, P0205, P0206, P0442, P0443, P0446, P0449, P0455, P0496 are not set. |
| • | DTCs P2A01, P0401, P0420 are not commanding fuel. |
| • | The system voltage is between 9-18 volts. |
| • | The scan tool special functions are not active. |
| • | The Engine Run Time parameter is more than 3 minutes. |
| • | The ECT Sensor parameter is more than 65°C (149°F). |
| • | The MAF sensor parameter is between 4 g/s and 30 g/s. |
| • | The Engine Speed parameter is between 650-2,500 RPM. |
| • | The HO2S Heater command parameter is not being activated by a scan tool. |
| • | The above conditions have been met for more than 7 seconds. |
Conditions for Setting the DTC
| • | The HO2S heater current is less than 0.23 amps or more than 0.90 amps for at least 17 out of 25 samples. Five test samples during each trip with a 30 second delay between each test sample. Each sample is 100 ms. |
| • | The PCM detects that the HO2S Heater Current parameter is less than 0.23 amps or more than 0.90 amps for more than 25 seconds during each test period, five test periods during each trip with a 30 second delay between each test period. |
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. |
Step | Action | Values | 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 - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||
2 |
Is the amperage within the specified range? | 0.23-0.90 A | Go to Step 3 | Go to Step 4 | ||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||
4 |
Important: Use a known good ground. DO NOT use the heated oxygen sensor (HO2S) 1 heater low control circuit or the HO2S 1 low signal circuit.
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 5 | ||||
5 | Test the HO2S 1 heater ignition 1 voltage fuse for an open. Refer to Circuit Testing in Wiring Systems. Is the fuse open? | -- | Go to Step 11 | Go to Step 15 | ||||
6 |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 9 | ||||
7 |
Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 8 | ||||
8 | Measure the resistance of the following circuits with a DMM:
Is the resistance of either circuit more than the specified value? | 5 ohms | Go to Step 16 | Go to Step 13 | ||||
9 | Test the HO2S 1 heater low control circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 14 | ||||
10 | Test the HO2S 1 heater low control circuit for a short to ground or a short to the HO2S 1 low signal circuit. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 14 | ||||
11 | Test the HO2S 1 heater ignition voltage circuit for a short to ground and replace the fuse. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 12 | ||||
12 | Test the HO2S 1 heater ignition 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 17 | Go to Intermittent Conditions | ||||
13 | Test for an intermittent and for a poor connection at the harness connector of the HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 17 | ||||
14 | Test for shorted terminals and for poor connections at the harness connector of 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 19 | Go to Step 18 | ||||
15 | Repair the open or high resistance condition in the HO2S 1 heater ignition voltage circuit. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 19 | -- | ||||
16 | Repair the circuit that measured high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 19 | -- | ||||
17 | Replace the HO2S 1. Refer to Heated Oxygen Sensor 1 Replacement . Did you complete the replacement? | -- | Go to Step 19 | -- | ||||
18 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 19 | Go to Step 2 | ||||
19 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 20 | ||||
20 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | ||||
