Circuit Description
The VCM supplies a voltage of about .45 V (450 mV) between the HO2S High and the HO2S Low circuits.
Important: If the voltage is measured using a 10 megohm digital voltmeter, the voltage may read as low as 0.32 V. The Heated Oxygen Sensor (HO2S) varies the voltage within a range of about 1 V (1000 mV) if the exhaust system is rich to as low as 0.10 V (10 mV) if the exhaust is lean.
When 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 Open Loop operation.
The HO2S heater provides for faster sensor warm-up which allows the sensor to become active in a shorter period of time and remain active during long extended idle. DTC P0161 determines if the HO2S heater is functioning properly by monitoring the amount of time necessary for the HO2S to become active after start-up. DTC P0161 is a type B DTC.
Conditions for Setting the DTC
| • | System Voltage is greater than 9 V but less than 17 V |
| • | MAF is less than 27 grams per second |
| • | Engine Coolant Temperature (ECT) is less than 32°C (90°F) |
| • | Intake Air Temperature (IAT) is less than 32°C (90°F) |
| • | The difference between the ECT sensor and the IAC sensor is no more than 5°C (41°F) |
| • | The time for the HO2S (Bank 2 sensor 2) to obtain ± 150 mV from 450 mV is to great |
Action Taken When the DTC Sets
The VCM will turn ON the malfunction indicator lamp (MIL) after two consecutive test cycles with the fault active.
Conditions for Clearing the MIL/DTC
The VCM turns OFF the MIL after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (the coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) during that same ignition cycle) or the scan tool clearing feature has been used.
Diagnostic Aids
Check for the following:
| • | Poor connection or damaged harness. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness. |
| • | Never solder the HO2S wires. |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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This step determines if DTC P0161 is the result of a hard failure or an intermittent condition. With the ignition ON, engine OFF, the HO2S (Bank 2 Sensor 2) voltage displayed on the scan tool should gradually change.150 V, indicating that the heater is working properly. HO2S voltage can rise as high as 975 mV before it toggles back down. The main thing to look for is a change.
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Probing terminal D of the HO2S (Bank 2 Sensor 2) connector verifies if voltage is available to the HO2S (Bank 2 Sensor 2) heater.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing DTC(s) use the scan tool to record Freeze Frame and Failure Records for reference, as data will be lost when the Clear Info function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Does the voltage displayed gradually decrease by the specified value? | 0.150 V (150 mV) | |||
Is the test light ON? | -- | |||
4 | Connect a test light between terminals C and D of the HO2S (Bank 2 Sensor 1) sensor connector. Is the test light ON? | -- | ||
5 | The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs are stored refer to those Table(s). Are any additional DTCs stored? | -- | Go to the Applicable DTC Table | |
6 | Check for an open in the HO2S (Bank 2 Sensor 2) sensor fuse. Is the HO2S (Bank 2 Sensor 2) fuse open? | -- | ||
7 | Check the connections at the HO2S (Bank 2 Sensor 2) sensor. Was a problem found? | -- | ||
8 | Check connections at HO2S (Bank 2 Sensor 2) sensor. Was a problem found? | -- | ||
9 | Check connections at HO2S (Bank 2 Sensor 2). Was a problem found? | -- | ||
10 | Repair the open HO2S (Bank 2 Sensor 2) sensor ground circuit. Is the action complete? | -- | -- | |
11 | Check for an open at the HO2S (Bank 2 Sensor 2) sensor ignition feed circuit. Was a problem found? | -- | -- | |
12 | Repair the faulty connection. Is the action complete? | -- | -- | |
13 | Repair the open in the HO2S (Bank 2 Sensor 2) sensor ignition feed circuit. Is the action complete? | -- | -- | |
14 | Repair the short to ground in the HO2S (Bank 2 Sensor 2) sensor ignition feed circuit and replace fuse. Is the action complete? | -- | -- | |
15 | Replace the HO2S (Bank 2 Sensor 2) sensor. Refer to Heated Oxygen Sensor Replacement . Is the action complete? | -- | -- | |
16 |
Does the scan tool indicate that this diagnostic Ran and Passed?
| -- | ||
17 | Using the scan tool, select Capture Info, Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go to the Applicable DTC Table | System OK |
