P0172
DTC P0172 Fuel Trim System RichSystem 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%). 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%). Whenever a rich condition is detected, the fuel trim values will read below 128 (0 to -100%), 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 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, 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 3400 RPM.
- Vehicle speed is below 116 kmph (72 mph).
- MAP is above 26 kpa.
- BARO is greater than 72 kPa.
- EVAP purge is not occurring.
Conditions for Setting the DTC
- Fuel Trim Index is below 70 (-46%).
- Above conditions present for over 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.
Steps 1 - 2:
Steps 3 - 5:
Steps 6 - 9:
Steps 10 - 13:
Steps 14 - 17:
Steps 18 - 20:
Steps 21 - 22:
Test Description
The number(s) below refer(s) to the step number(s) on the Diagnostic Table.
1. 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 scan tool stores this data for later reference.
5. A clogged air cleaner filter element restricts the airflow coming into the engine. This step checks the condition of the air cleaner filter.
17. A leaky fuel injector can cause a rich condition and set DTC P0172. Refer to Fuel Inj Coil Test - ECT Between 10 - 35 Degrees Cycles if for further diagnosis.
19. A loose TP sensor may not set a TP sensor related DTC, but could cause the system to become rich by a higher than actual TP reading.