Circuit Description
The PCM supplies a voltage of about 0.45 volt between the O2S signal and the ground circuit. The oxygen sensor (O2S 1) varies the voltage within the range of about 1.0 volt (1000 mV) if the exhaust is rich, down to about 0.1 volt (100 mV) if the exhaust is lean.
The sensor is like an open circuit and produces no voltage when it is below 360°C (600°F). An open sensor circuit or a cold sensor causes open loop operation. DTC 42 determines if the O2S 1 or the O2S 1 circuit has developed an open or the sensor is not switching.
If there is damage to the oxygen sensor pigtail wiring, the connector or the terminal, replace the entire oxygen sensor assembly. Do not attempt to repair the wiring, the connector or the terminals.
This is a type B DTC.
Conditions for Setting the DTC
| • | The vehicle is in CNG operation mode. |
| • | Closed loop operation. |
| • | The engine run time is greater than 120 seconds. |
| • | The oxygen sensor has been warm for at least 120 seconds. (The oxygen sensor is determined to be warm by the ECU if the ECT is greater than 40°C (104°F) and the calculated mass air flow is about 6 g/sec for at least 120 seconds.) |
| • | The O2S 1 sensor voltage is between 0.347 mV and 0.550 mV, or |
| • | The O2S 1 sensor showed no rich/lean activity for longer than 15 seconds. |
Action Taken When the DTC Sets
The MIL will be turned ON after two consecutive ignition cycles with test failures. The system will operate in open loop if any DTC of the O2S 1 is set.
Conditions for Clearing the MIL/DTC
The ECU turns the MIL OFF after three consecutive ignition cycles without a fault condition present. A DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 40°C (72°F) from the start-up coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during that same ignition cycle) or the code clearing procedure has been used.
Diagnostic Aids
Always diagnose ANY PCM codes that are present before beginning this diagnostic procedure.
A poor connection, rubbed through wire insulation, or a wire broken inside the insulation may cause an intermittent.
Inspect for the following conditions:
| • | A poor connection or a damaged harness. Inspect for the following conditions: |
| - | Backed out terminals |
| - | Improperly formed or damaged terminals |
| - | A poor terminal to wire connection |
| - | A damaged harness |
| • | The intermittent test. Monitor the O2S 1 signal voltage with a DVOM while moving the related connectors and the wiring harness. The engine should be warm and running at part throttle in closed loop. If the failure is induced, the O2S 1 signal voltage reading changes from its normal fluctuating voltage (above 600 mV and below 300 mV) to a fixed value around 450 mV. This may help isolate the location of the malfunction. |
Never solder the O2S 1 wires. For proper wire and connector repair, refer to Wiring Repairs in Engine Controls -- 2.2L in the J Platform Service Manual.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
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Removing the 20A CNG system fuse will force the system to start on gasoline. (The AF ECU is deactivated, but the Keep Alive Memory (KAM) contents is still retained.) The gasoline operation will then allow the PCM to enable the O2S 1 sensor diagnostics that may detect a similar fault, thereby isolating the fault to the base engine wiring harness or the O2S 1.
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This step determines if the fuel delivery system is the cause of DTC 42.
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This step determines if the ECU or the O2S 1 wiring is the cause of DTC 42 by isolating the AF system from the vase vehicle harness.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the AF Powertrain OBD System Check performed? | -- | Go to Step 2 | Go to Alternative Fuels (AF) Powertrain On Board (OBD) System Check |
The fuel indicator light will remain OFF due to the removal of the CNG system fuse. Is the action complete? | 1500 RPM | Go to Step 3 | -- | |
3 | Perform the AF Powertrain OBD System Check again. Is the action complete? | -- | Go to Step 4 | -- |
4 | Are there any powertrain DTCs displayed that have not been diagnosed? | -- | Go to the applicable powertrain DTC table | Go to Step 5 |
5 |
Does the DVOM indicate an O2S 1 voltage close to the scan tool voltage? | -- | Go to Step 6 | Go to Step 12 |
Perform the AF fuel system diagnosis. Refer to Fuel System Diagnosis . Was a problem found and repaired? | -- | Go to Step 16 | Go to Step 7 | |
7 |
Does the scan tool indicate that the O2S 1 voltage is within the values specified? | 407-509 mV | Go to Step 13 | Go to Step 8 |
Does the scan tool indicate that the O2S 1 voltage is within the value specified? | 407-509 mV | Go to Step 9 | Go to DTC P0134 O2S CKT Insuff. Activity in Engine Controls - 2.2L in the J Platform Service Manual | |
9 |
Was a problem found? | -- | Go to Step 15 | Go to Step 10 |
10 | Inspect for a poor connection at the ECU. Was a problem found? | -- | Go to Step 15 | Go to Step 11 |
11 | Replace the ECU. Refer to Engine Control Unit Replacement . Is the action complete? | -- | Go to Step 16 | -- |
12 |
Is the O2S 1 signal circuit resistance less than the specified value? | 1.0 ohms | Go to Diagnostic Aids | Go to Step 15 |
13 | Inspect the O2S 1 sensor electrical connector for damaged terminals or a poor connection. Was a problem found? | -- | Go to Step 15 | Go to Step 14 |
14 | Replace the O2S 1 sensor. Refer to Oxygen Sensor Replacement in Engine Controls - 2.2L in the J Platform Service Manual. Is the action complete? | -- | Go to Step 16 | -- |
15 | Repair the circuit as necessary. Refer to Wiring Repairs in Engine Electrical - 2.2L in the J Platform Service Manual. Is the action complete? | -- | Go to Step 16 | -- |
16 |
Did the MIL illuminate? | 1500 RPM | Go to Step 3 | Go to Step 17 |
17 | Are any ECU or PCM DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK |
