Fig 1: Correction Factor Graph (Closed Loop)

Courtesy of SAAB-SCANIA OF AMERICA, INC.

At a correction factor of 0.75, the system will read a rich air/fuel mixture and the fuel quantity has been reduced as much as possible. If this state persists for longer than 20 seconds, diagnostic trouble code P1172 will be generated. The fault can be caused by the following:
- Air leak between the compressor and the throttle.
- Purge valve stuck open.
- Defective mass air flow sensor.
- Fuel pressure too high.
Correspondingly, at a correction factor of 1.25, the system will read a lean air/fuel mixture and the fuel quantity has been increased as much as possible. If this state persists for longer than 20 seconds, diagnostic trouble code P1171 will be generated. The fault can be caused by the following:
- Air leak after the throttle.
- Low fuel pressure.
- Defective mass air flow sensor.
- Blocked injectors.
If closed loop fails to be activated within a reasonable time after start, diagnostic trouble code P0125 will be generated.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Diagnostics, closed loop