P0172

DESCRIPTION
The air/fuel control system, in addition to a number of sensors, includes the following components and systems:
- Intake air system.
- Exhaust system.
- Evaporative emissions control system (includes purge control solenoid valve).
- Fuel injectors.
- Fuel pressure regulator.
- Fuel pump.

For the air/fuel ratio to be within limits, all of the sensors, components and systems associated with the air/fuel control system must function within normal parameters.

FAILURE CONDITIONS

(FOR SHORT-TERM FUEL TRIM)
The ECM will set a code and the Malfunction Indicator Lamp (MIL) will turn on if the short-term fuel trim value goes 10% to 15% rich [for P0172] or if the short-term fuel trim additive value is less than 0.4 milliseconds, or 10% to 15% lean [for P0171] for 30 seconds during two driving cycles when the following conditions are met:
1. ECM is in closed loop operation.
2. Engine speed is below 1000 RPM.
3. Engine coolant temperature is above 158°F (70°C).
4. Canister purge system is not operating.
5. Mass air flow is less than 7.5 g/s [for P0172] or 5.5 g/s [for P0171].

(FOR LONG-TERM FUEL TRIM)
The ECM will set a code and the Malfunction Indicator Lamp (MIL) will turn on if the long-term multiplicative value is less than 77% for 30 seconds [for P1127] or if the long-term fuel trim value goes to 10% to 15% lean [for P1128] for 30 seconds during two driving cycles when the following conditions are met:
1. Engine load exceeds 1.8 milliseconds.
2. ECM is in closed loop operation [for P0171].
3. Engine coolant temperature is above 158°F (70°C).
4. Canister purge system is not operating.
5. Mass air flow is less than or 5.5 g/s.
6. Engine speed is below 1000 RPM [for P0172].

Test Procedure Part 1:

Test Procedure Part 2: