P0172

Diagnostic Chart:

SYSTEM DESCRIPTION

To provide the best possible combination of driveability, fuel economy, and emission control, a Closed Loop air/fuel metering system is used. While in Closed Loop, the PCM monitors the oxygen sensor signal voltage and adjusts fuel delivery based on the signal voltage. A change made to fuel delivery will be indicated by the long and short term fuel trim values which can be monitored with the scan tool. Ideal fuel trim values are around 128 (0 %), if the oxygen sensor signal is indicating a lean condition, the PCM will add fuel resulting in fuel trim values above 128 (0 % to 100 %). If a rich condition is detected, the fuel trim values will be below 128 (0 % to -100%), indicating that the PCM is reducing the amount of fuel delivered. It exhaust emissions reach an excessive level due to a lean or rich condition, a fuel trim DTC is set.

CONDITIONS FOR SETTING THE DTC

^ DTC's 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, P1406, 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 575 RPM and 3600 RPM.

^ Vehicle speed is below 70 mph (113 km/h).

^ MAP is above 38 kPa.

^ BARO is greater than 72 kPa.

^ Evaporative Emissions (EVAP) System purge is not occurring.

^ Fuel Trim Index is below 70 (-45 %).

^ Above conditions present for 16 seconds.

ACTION TAKEN WHEN THE DTC SETS

^ The Malfunction Indicator Lamp (MIL) will illuminate if the fault is active within the same conditions for two out of eighty ignition cycles.

Or

^ The MIL will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.

^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.

^ A history DTC is stored.

^ Coolant fan turns ON.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The MIL will turn OFF after three 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.

^ DTC(s) can be cleared by using a scan tool.

DIAGNOSTIC AIDS

^ Check for poor connection at PCM. Inspect harness connectors for the following conditions:

- Backed out terminals

- Improper mating

- Broken locks

- Improperly formed

- Damaged terminals

- Poor terminal to wire connection

^ Check for a damaged harness. Inspect wiring harness for damage. If the harness appears to be OK, observe the O2S 1 display on the scan tool while moving connectors and wiring harness related to the engine harness. A change in the display will indicate the location of the fault.

^ If a DTC P1406 is also set, check the 5 V reference circuits for a short to voltage.

TEST DESCRIPTION

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. 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 fault occurred. The information is then stored on the scan tool 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 injector can cause a rich condition and set DTC P0172. Refer to Fuel Injector Coil Test for further diagnosis.

19. A loose Throttle Position (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.