System Description
In order to provide the best possible combination of driveability, fuel economy, and emission control, a Closed Loop air and fuel metering system is used. While in a Closed Loop, the powertrain control module (PCM) monitors the oxygen sensor signal voltage. The PCM adjusts fuel delivery based on signal voltage. The Long and Short Term FT values will indicate a change made to the fuel delivery system. The ideal fuel trim values are around 128 (0 percent). Whenever the oxygen sensor signal is indicating a lean condition, the PCM will add fuel resulting in fuel trim values above 128 (0 to 100 percent). Whenever a rich condition is detected, the fuel trim values will read below 128 (0 to -100 percent), indicating that the PCM is reducing the amount of fuel. Whenever the exhaust emissions reach an excessive level due to a lean condition, a fuel trim DTC is set.
Conditions for Running the DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0200, P0300, P0301, P0302, P0303, P0304, P0325, P0335, P0341, P0342, P0446, P0502, P0503, P0506, P0507, P0601, P0602, P1133, and P1441 are not set. |
| • | The intake air temperature (IAT) is between -25°C (-13°F) and 115°C (175°F). |
| • | The engine coolant temperature (ECT) is between 60°C (140°F) and 115°C (239°F). |
| • | Engine speed is between 550 RPM and 3600 RPM. |
| • | Vehicle speed is below 132 km/h (82 mph). |
| • | MAP is above 26 kPa. |
| • | BARO is more than 72 kPa. |
| • | Fuel level is more than 9.8 percent. |
| • | Fuel Ethanol composition is less than 88 percent. |
Conditions for Setting the DTC
The fuel trim index is above 165.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) illuminates if the fault is active within the same conditions for 2 out of 80 ignition cycles. |
| OR |
| • | The MIL will illuminates after two consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records buffers stores this information. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault within the Freeze Frame conditions that the DTC failed. |
| • | A history DTC will clear after 40 consecutive warm up cycles without a fault. |
| • | A scan tool can clear the DTCs. |
Diagnostic Aids
If using the diagnostic tables does not isolate the problem, try monitoring the Long Term FT and fuel trim cell while operating the vehicle under various loads. This may isolate the condition which caused the setting of the current DTC.
A condition that causes the DTC P0300 Engine Misfire Detected may also set the current DTC; conversely an extremely lean condition which sets the current DTC can cause a misfire at idle and the DTC P0300 to set. If the cause of the current DTC cannot be determined and the DTC P0300 is also set, refer to DTC P0300 Engine Misfire Detected .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the Freeze Frame and Failure Records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The information then stores on the scan tool for later reference.
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This step checks for a partially grounded O2S1 signal circuit. Under some conditions, such as light throttle and limited drive time with some voltage present in the signal circuit, an O2 code may not set immediately, and the fuel system lean code may be the only code presently set.
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The testing of these components are grouped later in the diagnostic as the earlier steps are more likely to cause the fault. However these items should all be considered possible cause for this DTC to set. If no correction has been found with this step, Diagnostic Aids will give some other possibilities.
Step | Action | Values | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||||||||||||||
2 |
Are any component related DTCs set? | -- | Go to Component DTC table | |||||||||||||
3 |
Is the Long Term FT at the specified value or more? | 21% | ||||||||||||||
4 |
Is the Long Term FT at the specified value or more? | 21% | ||||||||||||||
5 | With the engine at idle, read the O2S1 and HO2S2 on the scan tool Does the O2S1 read under 350 mv with the HO2S2 reading above 800 mv? | -- | ||||||||||||||
6 | Check the O2S1 signal circuit for a short to ground or poor connection and repair as necessary. Was a problem found? | 21% | ||||||||||||||
7 | Check for low fuel pressure. Refer to Fuel System Diagnosis . Was a problem found? | -- | ||||||||||||||
8 | Perform the Fuel Injector Balance Test. Refer to Fuel Injector Balance Test . Was a problem found? | -- | ||||||||||||||
9 | The Lean condition is not present. Does a driveability problem exist? | -- | Go to Symptoms | Go to Diagnostic Aids | ||||||||||||
Check the following components for proper operation :
Repair as needed. Was a repair made? | -- | Go to Diagnostic Aids | ||||||||||||||
11 |
Does the scan tool indicate that this diagnostic has Ran and Passed? | -- | ||||||||||||||
12 | Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC table | System OK |
