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 PCM monitors the oxygen sensor signal voltage. The PCM adjusts fuel delivery based on signal voltage. The long and short term fuel trim values will indicate a change made to the fuel delivery. 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 delivered. Whenever the exhaust emissions reach an excessive level due to a rich condition, a fuel trim DTC will set.
Conditions For Setting The DTC
| • | When one or more of the following DTCs are not set P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0300, P0301, P0302, P0303, P0304, P0325, P0335, P0341, P0342, P0401, P0502, P0503, P0506, P0507, P0601, P1133, P1406, P1441. |
| • | The fuel Trim Index is less than 70. |
| • | The engine coolant temperature is between 60° C (140° F) and 115° C (239° F). |
| • | The IAT sensor is between -25° C (-13° F) and 115° C (239° F). |
| • | The engine speed is between 750 and 3400 RPM (auto). |
| • | The engine speed is between 800 and 4000 RPM (manual). |
| • | The vehicle speed is below 70 mph. |
| • | The MAP is greater than 28 kPa. |
| • | The BARO is greater than 70 kPa. |
| • | The EVAP Canister purge is not occurring. |
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
| • | Check for a poor connection at the PCM. Inspect harness connectors for the following conditions: |
| - | Backed out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | Poor terminal to wire connection |
| • | Check for a damaged harness. If the harness appears to be OK, observe the O2S 1 display on the scan tool while moving the connectors and wiring harness related to the engine harness. A change in the display will indicate the location of the fault. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This information on the scan tool can be referred to later.
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A loose TP sensor may not set a TP sensor related DTC, but may cause the system to become rich by a higher than actual TP reading.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||
2 | Any component related DTCs set? | -- | Go to the Component DTC Table | |
3 |
Is the Fuel Trim Index above the specified value? | 70 | ||
4 |
Does the Fuel Trim Index go below the specified value while operating under the specified conditions? | 70 | ||
5 |
Did the air cleaner filter require replacement? | -- | ||
6 |
Did the air intake system require repair? | -- | ||
7 |
Did the inspection of the throttle body reveal a condition requiring repair or replacement? | -- | ||
8 |
Did the inspection reveal a condition requiring repair? | -- | ||
9 |
Is a low or unsteady idle being experienced? | -- | ||
10 | With the engine idling. Are the IAC counts below the specified value? | 100 | ||
11 |
Does the Fuel Trim Index increase above the specified value? | -- | ||
12 |
Did the inspection reveal a condition requiring repair? | -- | ||
13 |
Did the fuel pressure regulator require replacement? | -- | ||
14 |
Does the Throttle Position display increase steadily and evenly from its minimum voltage at closed throttle to its maximum voltage at wide-open throttle? | -- | ||
15 |
Did the table isolate a problem requiring repair? | -- | ||
16 |
Was a problem isolated that required a repair? | -- | ||
17 |
Did the Injector Balance/Coil Test isolate a problem requiring repair? | -- | ||
18 |
Was contamination present? | -- | Go to Diagnostic Aids | |
19 |
Is the action complete? | -- | -- | |
20 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Is the action complete? | -- | -- | |
21 |
Does the scan tool indicate that this diagnostic ran and passed? | 90°-95° C | ||
22 | Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to the Applicable DTC Table | System OK |
