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
| • | DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0200, P0300, P0301, P0302, P0303, P0304, P0325, P0335, P0341, P0342, P0401, P0404, P0405, P0502, P0503, P0506, P0507, P0601, P0602, P1404, P1133, and P1441, not set. |
| • | Intake Air Temperature (IAT) is between -25°C (-13°F) and 115°C (175°F). |
| • | Engine Coolant temperature is between 60°C (140°F) and 115°C (239°F). |
| • | Engine speed is between 550 RPM and 3,400 RPM.(Auto) |
| • | Engine speed is between 850 RPM and 3,400 RPM.(Man) |
| • | Vehicle speed is below 72 mph (116 km/h). |
| • | MAP is above 26 kPa. |
| • | BARO is greater than 72 kPa. |
| • | EVAP purge is not occurring. |
| • | Fuel Trim Index is below 75 (-42%). |
| • | Above conditions present for 16 seconds. |
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
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
-
A clogged air cleaner filter element restricts the airflow coming into the engine. This step checks the condition of the air cleaner filter.
-
A leaky injector can cause a rich condition and set DTC P0172. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) for further diagnosis.
-
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 | Are any component related DTCs set? | -- | Go to Component DTC table | |
3 |
Is the Fuel Trim Index below the specified value? | -42% | ||
4 |
Does the Fuel Trim Index go below the specified value while operating under the specified conditions? | -42% | ||
Did the air cleaner filter require replacement? | -- | |||
6 |
Did the air intake system require repair? | -- | ||
7 | Inspect the throttle body inlet for damage or foreign objects which may partially block the airflow and correct any problem found. Did the inspection of the throttle body reveal a condition requiring a repair or replacement? | -- | ||
8 |
Did the inspection reveal a condition requiring a repair? | -- | ||
9 | Start the engine with the vehicle in park or neutral and A/C OFF and note the idle quality. 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? | -42% | ||
12 |
Did the inspection require any repairs? | -- | ||
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 a repair? | -- | ||
16 |
Was a problem isolated that requiring a repair? | -- | ||
Did the table isolate a problem requiring a repair? | -- | |||
18 |
Was contamination present? | -- | Go to Diagnostic Aids | |
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 has ran and passed? | -- | ||
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 |
