Circuit Description
The heated oxygen sensor (HO2S) heater is a device used in order to reduce the time that the sensor takes to go active. The powertrain control module (PCM) controls the HO2S heaters using a high side driver, two low side drivers, and a current monitoring driver. The current monitoring driver tests the condition of the heaters. The high side driver provides the HO2S bank 1 sensor 1 heater with ignition voltage. A fused ignition feed provides bank 1 sensor 2, and bank 2 sensor 1 with ignition voltage. HO2S bank 1 sensor 1, and bank 2 sensor 1 receive ground through one of the low side drivers. HO2S bank 1 sensor 2 receives ground through a separate low side driver.
With the engine running, the PCM turns ON the high side, and the low side drivers to warm the oxygen sensors. When the proper conditions are present, the PCM keeps the high side driver ON, turns ON the current monitor driver, and then turns OFF the warm-up driver. This allows the PCM to record a total current value for both of the fuel control heaters. If the test conditions remain stable, the PCM enters the second stage of the test. During this stage, the PCM keeps the current monitor ON, and turns OFF the high side driver. This allows the PCM to record a current value for the bank 2 sensor 1 heater circuit. The PCM subtracts the bank 2 sensor 1 current value from the total current value to determine the current value for bank 1 sensor 1. If the PCM detects a bank 2 sensor 1 current value outside the calibrated range, the diagnostic trouble code (DTC) will set.
Conditions for Running the DTC
| • | DTCs P0030, P1031, or P1032 are not set. |
| • | The system voltage during the current measurement is steady within 1 volt of actual system voltage. |
| • | The engine speed is between 500-3,000 RPM. |
| • | The engine run time is more than 180 seconds. |
| • | The MAF is between 4-30 grams per second. |
| • | All of the above conditions are met for 3 seconds. |
Conditions for Setting the DTC
The PCM detects a bank 2 sensor 1 current value outside the calibrated range.
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
Notice: Do not solder heated oxygen sensor wires. Soldering the wires will result in the loss of the air reference to the sensor. Refer to Engine Electrical for proper wire and connection repair techniques.
If the condition is intermittent, refer to Intermittent Conditions .
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||
2 |
Are DTCs P0030, P1031, and P1032 set? | -- | Go to Step 3 | |||||||
3 |
Are DTCs P0135 and P0155 set? | -- | Go to Step 4 | |||||||
4 | Is DTC P0155 set? | -- | Go to Step 5 | Go to Intermittent Conditions | ||||||
5 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 6 | ||||||
6 |
Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury. Does the voltage measure near the specified value? | 5 V | Go to Step 8 | Go to Step 7 | ||||||
7 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | ||||||
8 | Inspect for poor connections at the harness connector of the HO2S bank 2 sensor 1. 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 12 | Go to Step 10 | ||||||
9 | Inspect for poor connections at the harness connector of the 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 12 | Go to Step 11 | ||||||
10 | Replace HO2S bank 2 sensor 1. Refer to Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||
11 | Replace the PCM. Refer Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||
12 |
Does the DTC run and pass? | -- | Go to Step 13 | Go to Step 2 | ||||||
13 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||
