Circuit Description
The oxygen sensor (O2S) is used in order to determine the oxygen content of the engine's exhaust. The oxygen content of the exhaust indicates when the engine is operating lean or rich. When the engine is operating lean the exhaust will have more oxygen content. Once at operating temperature, the O2S will produce a voltage in relation to the oxygen content of the exhaust. The O2S requires an operating temperature of 360°C (600°F) to produce voltage. The O2S will produce more voltage when the exhaust is rich and less voltage when the exhaust is lean. The O2S operating voltage range is around 0.10 volts (100 mV) to 1 volt (1000 mV).
The gasoline control module (VCM / PCM or ECM) supplies a bias (or reference) voltage to the HO2S. This bias voltage is around 450 millivolts.
This DTC is used to indicate an O2S signal voltage that is below the normal operating range of the sensor.
Conditions for Running the DTC
| • | The engine is operating on alternative fuel. |
| • | Engine speed is greater than 500 RPM. |
| • | Engine coolant temperature is above 70°C (160°F). |
| • | The AF ECU determines the O2S has been at operating temperature for at least 2 minutes. The engine coolant temperature must be greater than 40°C (104°F) AND the calculated mass air flow must be above 6 grams per second for 2 minutes in order for the AF ECU to determine the O2S is at operating temperature. |
| • | The AF ECU is operating in Closed Loop fuel control. |
Conditions for Setting the DTC
The AF ECU monitors an O2S signal voltage of less than 0.02 volts (20 mV) for 6 seconds continuously.
Action Taken When the DTC Sets
The AF ECU will operate in Open Loop fuel control.
| • | A first failure of this DTC will NOT illuminate the MIL and will store as Last Test Failed but not as History. |
| • | The AF ECU will illuminate the MIL and store the DTC as History after TWO consecutive drive trips that the diagnostic runs and fails. |
| • | The AF ECU will record operating conditions at the time the DTC sets. This information will be stored as Freeze Frame data. |
Conditions for Clearing the MIL/DTC
| • | The Last Test Failed status will clear when the DTC runs and passes. |
| • | The AF ECU will turn OFF the MIL after 3 consecutive drive trips that the DTC runs and passes. |
| • | The History status will clear after 40 consecutive WARM-UP cycles with NO failures of ANY DTC. |
| • | All DTC Information can be cleared using a scan tool. |
| • | Interruption of Control Module (AF ECU / VCM / PCM or ECM) power or ground MAY clear DTC Information. Clearing DTC Information with this method is inconsistent and should not be performed. |
Diagnostic Aids
Intermittent Condition
A fault not present indicates the condition that caused the DTC to set is intermittent and not currently present. Refer to Intermittent Conditions diagnostic information located in Symptoms-Engine Controls. If any additional DTCs were stored, proceed to the applicable DTC table in the order stated in the Diagnostic System Check - Alternative Fuels (Engine Controls) .
Step | Action | Value(s) | Yes | No | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Alternative Fuels Engine Controls Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - Alternative Fuels (Engine Controls) | ||||||||||||||||||||
2 |
Is the O2S voltage fixed less than the value specified? | 20 mV | Go to Step 5 | Go to Step 3 | ||||||||||||||||||||
3 | The condition that set this DTC is not present. This DTC may have been set by one of the following conditions:
Was a condition found and repaired? | -- | Go to Step 16 | Go to Step 4 | ||||||||||||||||||||
4 | The fault is not present. Refer to Diagnostic Aids. Are any DTCs stored that have not been diagnosed? | -- | Go to Intermittent Conditions | |||||||||||||||||||||
5 |
Is the O2S voltage fixed less than the value specified? | 20 mV | Go to Step 6 | Go to Step 11 | ||||||||||||||||||||
6 |
Is the O2S voltage fixed less than the value specified? | 20 mV | Go to Step 7 | Go to Step 12 | ||||||||||||||||||||
7 |
Is the O2S voltage WITHIN the value range specified? | 351-551 mV | Go to Step 8 | Go to Step 9 | ||||||||||||||||||||
8 | The O2S may be detecting a lean exhaust condition. Inspect for one of the following conditions:
Repair any of the above or similar engine conditions as necessary. Was a condition found and repaired? | -- | Go to Step 16 | Go to Step 14 | ||||||||||||||||||||
9 |
Is infinite resistance measured on both tests? | ∞ | Go to Step 15 | Go to Step 10 | ||||||||||||||||||||
10 | Repair the O2S signal High circuit shorted to ground or shorted to the O2S Low circuit. Is the action complete? | -- | Go to Step 16 | -- | ||||||||||||||||||||
11 |
Was a wiring or terminal repair made? | -- | Go to Step 16 | Go to Step 13 | ||||||||||||||||||||
12 | The HO2S may be detecting a lean exhaust condition only during CNG operation. Perform the Fuel System Diagnosis and return to this step. Was a lean AF fuel system condition found and repaired? | -- | Go to Step 16 | Go to Step 13 | ||||||||||||||||||||
13 |
Is the replacement complete? | -- | Go to Step 16 | -- | ||||||||||||||||||||
14 | Replace the O2S. Refer to Oxygen Sensor Replacement in Engine Controls-2.2L (LN2) in the J Platform Service Manual. Is the action complete? | -- | Go to Step 16 | -- | ||||||||||||||||||||
15 |
Important: The following control module replacement procedures must all be completed before attempting to operate the vehicle.
Important: In order to perform the variation learn procedure a switch-over to gasoline operation is necessary. Remove the CNG 20 amp fuse in order to perform the switch-over. All of the above procedures are located in the gasoline service manual. Is the replacement complete? | -- | Go to Step 16 | -- | ||||||||||||||||||||
16 |
Does the scan tool indicate the DTC passed? | -- | System OK | Go to Step 2 |
