Circuit Description: Notes

The intake air flow system performance diagnostic provides the within-range rationality test for the mass air flow (MAF), the supercharger inlet pressure (SCIP), and the throttle position (TP) sensors. This is an explicit model-based diagnostic containing four separate models for the intake system.

• The throttle model describes the flow through the throttle body and is used to estimate the MAF through the throttle body as a function of barometric pressure (BARO), throttle position, intake air temperature (IAT), and estimated SCIP.
• The first intake manifold model describes the intake manifold and is used to estimate SCIP as a function of the MAF into the intake manifold from the throttle body and the MAF out of the intake manifold caused by engine pumping. The flow into the intake manifold from the throttle uses the MAF estimate calculated from the throttle model.
• The second intake manifold model is identical to the first intake manifold model except that the MAF sensor measurement is used instead of the throttle model estimate for the throttle air input.
• A fourth model is created from the combination and additional calculations of the throttle model and the first intake manifold model.

The estimates of the MAF, the SCIP, and the TP that are obtained from this system of models and calculations are then compared to the actual measured values from the MAF, the SCIP, and the TP sensors and to each other to determine the appropriate DTC to fail. The following table illustrates the possible failure combinations and the resulting DTC or DTCs.

If the powertrain control module (PCM) detects that the actual measured air pressure from the SCIP sensor is not within range of the calculated air pressure for the SCIP sensor that is derived from the system of models, DTC P1182 sets.