| Table 1: | HO2S Voltages |
Circuit Description
The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust system and provides more information than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell, and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The powertrain control module (PCM) supplies a voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the PCM controls the pump current through the oxygen pumping cell in order to maintain a constant voltage in the oxygen sensing cell. The PCM monitors the voltage variation in the sensing cell and attempts to keep the voltage constant by increasing or decreasing the amount of current flow, or oxygen ion flow, to the pumping cell. By measuring the amount of current required to maintain the voltage in the sensing cell, the PCM can determine the concentration of oxygen in the exhaust. The HO2S voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the fuel system is lean, the oxygen level will be high and the lambda signal will be high or more than 1. When the fuel system is rich, the oxygen level will be low, and the lambda signal will be low or less than 1. The PCM uses this information to maintain the correct air/fuel ratio. If the ECM detects an HO2S voltage that stays above or below an expected value during a fuel cutoff condition, this DTC sets.
DTC Descriptors
This diagnostic procedure supports the following DTCs.
| • | DTC P2297 HO2S Performance During Decel Fuel Cut-Off (DFCO) Bank 1 Sensor 1 |
| • | DTC P2298 HO2S Performance During Decel Fuel Cut-Off (DFCO) Bank 2 Sensor 1 |
Conditions for Running the DTC
| • | DTCs P0030, P0050, P0112, P0113, P0117, P0118, P0122, P0123, P0133, P0135, P0155, P0171, P0172, P0174, P0175, P0222, P0223, P0300-P0306, P0443, P0496, P0501, P0502, P0641, P2100, P2101, P2108, P2122, P2123, P2127, P2128, P2135, P2138, P2176, P2195, P2227, P2228, P2229, P2238, P2239, P2241, P2242, P2243, P2247, P2252, P2253, P2255, P2256, P2414, P2415, P2627, P2628, P2630, P2631, and U0107 are not set. |
| • | Engine coolant temperature (ECT) at least 69°C (156°F). |
| • | Intake air temperature (IAT) is at least -13°C (8°F). |
| • | Engine speed is less than 2,600 RPM. |
| • | Vehicle speed is at least 48 km/h (30 mph) at the start of engine decel. |
| • | The EVAP monitor is not running. |
| • | The HO2S heater has been commanded ON for more than 60 seconds. |
| • | DTC P2297 and DTC P2298 run once per drive cycle when the above conditions are met. |
Conditions for Setting the DTC
| • | The HO2S signal voltage is more or less than the expected value during a closed throttle decel lasting at least 4 seconds. |
| • | The above condition is met for at least 6 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 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
| • | Use the J 35616 Connector Test Adapter Kit for any test that requires probing the PCM harness connector or a component harness connector. |
| • | The Loop Status for the respective bank will default to Open when the DTC is current. |
| • | The wide band sensors do not toggle or switch like a switching HO2S. The HO2S signals will be relatively stable for an idling engine. |
| • | Inspect for fuel contamination--Small amounts of water can be delivered to the fuel injectors and cause a lean exhaust indication. A lean exhaust indication can also be caused by too much alcohol in the fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis . |
| • | Inspect the HO2S bank 1 or bank 2 sensor 1 for water intrusion into the wiring harness and the sensor housing. Water can create a short to voltage in the HO2S signal circuit causing a false rich indication. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
| • | The following table illustrates the typical voltages for the HO2S circuits: |
| |||||
|---|---|---|---|---|---|
HO2S Circuit | Voltage | ||||
Heater Control | Less than 0.5 V | ||||
Heater Supply Voltage | B+ | ||||
Reference Voltage | 3.3-3.8 V | ||||
Low Reference | 5.9-6.4 V | ||||
Pump Current | 4.8-5.3 V | ||||
Input Pump Current | 3.3-3.8 V | ||||
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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This step determines wether a condition currently exists.
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This step isolates the condition. If the DTC for only one bank sets, inspect and test for a condition that would affect only one bank of the engine.
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 | ||||||||||||||||||||||||||
Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | ||||||||||||||||||||||||
|
Important:
Did the DTC fail this ignition? | -- | Go to Step 3 | Go to Diagnostic Aids | |||||||||||||||||||||||
Did a DTC for both banks set? | -- | Go to Step 4 | Go to Step 5 | |||||||||||||||||||||||
4 | Visually and physically inspect for any of the following conditions:
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 6 | ||||||||||||||||||||||
5 | Visually and physically inspect for any of the following conditions:
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 6 | ||||||||||||||||||||||
6 | Test for an intermittent and for a poor connection at the HO2S sensor. 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 8 | Go to Step 7 | ||||||||||||||||||||||
7 | Replace the HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 . Did you complete the replacement? | -- | Go to Step 8 | -- | ||||||||||||||||||||||
8 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 9 | ||||||||||||||||||||||
9 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||||||||||||||
