Circuit Description
Important: If this voltage is measured by using a 10 megaohm digital voltmeter, the voltage may read as low as 0.32 volt.
The Heated Oxygen Sensor (HO2S) varies the voltage within a range of about 1.0 volt (1000 mV) if the exhaust is rich to as low as 0.10 volt (10 mV) if the exhaust is lean.
The VCM supplies a reference voltage of approximately 0.45 volts (450 mV) to the Heated Oxygen sensor (HO2S) on the HO2S High signal circuit. When the Heated Oxygen sensor is cold, less than 200°C (392°F), the Heated Oxygen sensor signal voltage will read around 0.45 volt, and the VCM will keep the system in an Open Loop operation. When the Heated Oxygen sensor is warm, above 200°C (392°F), the Heated Oxygen sensor will swing from rich to lean rapidly, at least 1 swing every 2 seconds, if the VCM is in control of the air fuel mixture. This DTC sets if the Oxygen sensor is slow to respond to changes in the exhaust oxygen content.
When the HO2S temperature is below 360°C (600°F), the sensor will not produce any voltage and will behave like an open circuit. This will result in an Open Loop operation.
The HO2S heater provides for a faster sensor warm-up. This allows the sensor to become active in a shorter period of time and remain active during a long extended idle. This DTC is a type B DTC.
Conditions for Setting the DTC
The following conditions sets the DTC:
| • | No fuel trim DTCs |
| • | No TP sensor DTCs |
| • | No EVAP DTCs |
| • | No IAT sensor DTCs |
| • | No MAP DTCs |
| • | No EGR DTCs |
| • | No ECT sensor DTCs |
| • | The DTC P0155 not set |
| • | Closed Loop |
| • | HO2S voltage between 0.300 volts and 0.600 volts |
| • | Throttle position is greater than 10% but less than 20%. |
| • | L/R switches less than 50. |
| • | R/L switches less than 50. |
Action Taken When the DTC Sets
The VCM turns the MIL (Malfunction Indicator Lamp) ON when the diagnostic runs and fails.
The VCM records the operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records store this information.
Conditions for Clearing the MIL/DTC
The VCM turns the MIL OFF after 3 consecutive drive trips that the diagnostic runs and does not fail.
A Last Test Failed (current) DTC clears when the diagnostic runs and does not fail.
A History DTC clears after 40 consecutive warm-up cycles with no failures of any emission related diagnostic test.
The VCM battery voltage is interrupted.
The scan tool Clear Info function is used.
Diagnostic Aids
Never solder the HO2S wires. For a proper wire and connector repair refer to Wiring Repairs in Engine Electrical.
Test Description
The numbers below refer to the step numbers in the diagnostic table.
-
This step checks to see if the other causes of this DTC have already been diagnosed.
-
Diagnose other DTCs first because they may have set this DTC.
-
With the engine running warm, coolant at least 85° C (185° F) and at fast idle, the HO2S voltage should rapidly swing above 0.60 volts and below 0.30 volts.
-
This step checks to see if the Oxygen sensor voltage is swinging between rich and lean very slowly or not at all.
-
This step checks for causes of the HO2S failure. If the sensor is replaced without finding the cause of the contamination, the replacement sensor may become contaminated.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool to record the Freeze Frame and the Failure Records for reference. This data will be lost when the Clear Info function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||
Connect the scan tool. Are any other DTC stored? | -- | Go to The Applicable DTC Table | ||||||||
After 2 minutes does the HO2S (Bank 2, Sensor 1) voltage rapidly swing above and below the specified value? | 1200-2000 RPM 0.30 V-0.60 V | |||||||||
With the engine running at the specified value, observe the scan tool display. Does the scan tool display indicate a Closed Loop? | 1200-2000 RPM | Refer to Diagnostic Aids | ||||||||
5 | Does the front HO2S (Bank 2, Sensor 1) voltage stay within the specified value longer than it swings outside this value? | 0.30 V-0.60 V | ||||||||
Check the VCM connector terminal contact at the H02S Front High and Low signal circuits. Was a problem found? | -- | |||||||||
7 | Check for a poor connection at the HO2S Bank 2, Sensor 1) connector. Was a problem found? | -- | ||||||||
8 | Replace the HO2S (Bank 2, Sensor 1). Refer to Heated Oxygen Sensor (HO2S) Replacement . Is the action complete? | -- | -- | |||||||
Check the following for possible cause of Oxygen sensor contamination:
Was a problem found? | -- | |||||||||
10 | Repair as necessary. Replace as necessary. Is the action complete? | -- | -- | |||||||
11 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||||||||
12 | Using the scan tool, select the Capture Info and the Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go to The Applicable DTC Table | System OK |
