P012B
DTC P012B
CIRCUIT DESCRIPTION
IMPORTANT: The following applies to the intake air flow system performance diagnostic that is used in this supercharged engine:
- When referring to the "intake manifold models", the plenum volume between the throttle body (TB) and the supercharger is considered to be the intake manifold.
- When referring to "engine pumping", the supercharger and the intercooler plenum are considered to be part of the engine.
- The manifold absolute pressure (MAP) sensor that resides in the engine intake manifold is used to adjust the engine air flow estimates to balance the air flow models.
The supercharger inlet absolute pressure (SCIAP) sensor measures the absolute pressure of the air just after the TB, thus just before the supercharger. The plenum volume between the TB and the supercharger is where this sensor is located, and for the purpose of this diagnostic, this area is considered to be the intake manifold. The diaphragm within the SCIAP sensor functions in the same manner as the barometric pressure (BARO) sensor. These sensors are not interchangeable.
The intake air flow system performance diagnostic provides the within-range rationality test for the mass air flow (MAF), the SCIAP, 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 BARO, throttle position, intake air temperature (IAT), and estimated SCIAP.
- The first intake manifold model describes the intake manifold and is used to estimate SCIAP 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 SCIAP, 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 SCIAP, and the TP sensors and to each other to determine the appropriate DTC to fail. The table illustrates the possible failure combinations and the resulting DTC or DTCs.
If the engine control module (ECM) detects that the actual measured air pressure from the SCIAP sensor is not within range of the calculated air pressure for the SCIAP sensor that is derived from the system of models, DTC P012B sets.
DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P012B Supercharger Inlet Absolute Pressure (SCIAP) Sensor Performance
CONDITIONS FOR RUNNING THE DTC
- DTCs P0120, P0121, P0220, P0506, P0507, P012C, P012D, P2135 are not set.
- The engine speed is between 400-6,400 RPM.
- The engine coolant temperature (ECT) is between 70-125°C (158-257°F).
- The IAT is between -7 to +125°C (+19 to +257°F).
- The change in the TP is less than 5 percent.
- The above enabling criteria must be stable for more than 5 seconds.
- DTC P012B runs continuously when the above conditions are met.
CONDITIONS FOR SETTING THE DTC
The ECM detects that the actual measured air pressure from the SCIAP sensor is not within range of the calculated air pressure for the SCIAP sensor that is derived from the system of models by more than 20 kPa for more than 0.5 second.
ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.
TEST
