Circuit Description
The intake flow rationality diagnostic provides the within-range rationality check for the mass air flow (MAF), manifold absolute pressure (MAP), and the throttle position (TP) sensors. This is an explicit model-based diagnostic containing 4 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), TP, intake air temperature (IAT), and estimated MAP. |
| • | The first intake manifold model describes the intake manifold and is used to estimate MAP as a function of the MAF into the manifold from the throttle body and the MAF out of the manifold caused by engine pumping. The flow into the manifold from the throttle uses the MAF estimate calculated from the above 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 MAF and MAP obtained from this system of models and calculations are then compared to the actual measured values from the MAF, MAP, 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.
Throttle Model | First Intake Manifold Model | Second Intake Manifold Model | Fourth Model | DTCs Passed | DTCs Failed |
X | X | Pass | Pass | P0101 P0106 P0121 P1101 | None |
Pass | Pass | Failed | Pass | P0101 P0106 P0121 P1101 | None |
Failed | Pass | Failed | Pass | P0106 P0121 P1101 | P0101 |
Pass | Failed | Failed | Pass | P0101 P0121 P1101 | P0106 |
Failed | Failed | Failed | Pass | P0121 P1101 | P0101 P0106 |
X | X | Pass | Failed | P0101 P0106 P1101 | P0121 |
Pass | Pass | Failed | Failed | P0101 P0106 P0121 P1101 | None |
Failed | Pass | Failed | Failed | P0101 P0106 P0121 | P1101 |
X | Failed | Failed | Failed | P0101 P0106 P0121 | P1101 |
If the powertrain control module (PCM) detects that the actual measured airflow from MAF, MAP, and TP is not within range of the calculated airflow that is derived from the system of models, DTC P1101 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1101 Intake Air Flow System Performance
Conditions for Running the DTC
| • | DTCs P0102, P0103, P0112, P0113, P0107, P0108, P0117, P0118, P0335, P0336 are not set. |
| • | The engine speed is between 400-6,400 RPM. |
| • | The IAT Sensor parameter is between -7 to +125°C (19-257°F). |
| • | The ECT Sensor parameter is between 70-125°C (158-257°F). |
| • | This DTC runs continuously when the above conditions are met. |
Conditions for Setting the DTC
The PCM detects that the actual measured airflow from MAF, MAP, and TP is not within range of the calculated airflow that is derived from the system of models 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. |
Diagnostic Aids
| • | Any condition that can cause the MAF, MAP, and TP sensors to be shifted in value at the same time will cause this DTC to set. |
| • | Inspect the harness of the MAF sensor to verify that it is not routed too close to the following components: |
| - | Any aftermarket accessories--Refer to Checking Aftermarket Accessories. |
| - | Any solenoids |
| - | Any relays |
| - | Any motors |
| • | A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 3-6 g/s at idle to 140 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system. |
| • | A skewed or stuck engine coolant temperature (ECT) or IAT sensor will cause the calculated models to be inaccurate and may cause this DTC to run when it should not. |
| • | A steady or intermittent high resistance of 15 ohms or more on the ignition 1 voltage circuit will cause the MAF sensor values to be skewed high by up to 60 g/s, and may cause this DTC to set. A high resistance will cause a driveability concern before this DTC sets. |
| • | The BARO that is used by the PCM to calculate the air flow models is initially based on the MAP sensor at key ON. When the engine is running, the PCM will continually update the BARO value near WOT using the MAP sensor and a calculation. A skewed MAP sensor will cause the calculated mass air flow value to be inaccurate and may result in a no start condition. With the ignition ON and the engine OFF, the MAP Sensor parameter varies with the altitude. 101 kPa is the approximate value near sea level. This value will decrease by approximately 3 kPa for every 305 meters (1,000 feet) of altitude. |
| • | A high resistance on the low reference circuit of the MAP sensor will skew the sensor value and may cause this DTC to set. |
| • | A short to battery voltage on the 5-volt reference circuit of the MAP sensor will cause this DTC to set. |
| • | If the condition is intermittent, refer to Testing for Intermittent Conditions and Poor Connections. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step will determine if any mechanical faults have caused this DTC to set.
-
This voltage drop test will determine if high resistance has caused this DTC to set.
-
This step verifies the voltage signal from the PCM to the MAF sensor connector.
-
This step will determine if the PCM can accurately process the frequency signal that it receives from the MAF sensor.
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This step will determine if an abnormal resistance of less than 1,150 ohms has skewed the MAF sensor frequency signal.
Step | Action | Values | Yes | No | ||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views | ||||||||||||||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||||||||||||||||||
2 |
Important: A stalling condition created by any of the following DTCs may cause this DTC to set. Are DTCs P0641, P0651, P1516, P2101, P2119, or P2135 set? | -- | Go to Step 3 | |||||||||||||||||||||||||
3 |
Important: This diagnostic routine may have to be followed more than once. Attempt to start the engine. Does the engine start? | -- | Go to Step 4 | Go to Step 5 | ||||||||||||||||||||||||
4 |
Did the DTC fail this ignition? | -- | Go to Step 5 | Go to Diagnostic Aids | ||||||||||||||||||||||||
Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 6 | |||||||||||||||||||||||||
6 |
Important:: The Altitude vs. Barometric Pressure (BARO) table indicates a pressure range for a given altitude under normal weather conditions. Weather conditions consisting of very low or very high pressure and/or temperature may cause a reading to be slightly out of range.
Is the MAP sensor pressure within the specified range as indicated on the Altitude vs. Barometric pressure table? | -- | Go to Step 7 | Go to DTC P0106 | ||||||||||||||||||||||||
7 |
Does the MAP Sensor kPa parameter decrease? | -- | Go to Step 8 | Go to DTC P0106 | ||||||||||||||||||||||||
8 |
Does the MAP Sensor parameter change to within 5 kPa of the BARO parameter? | -- | Go to Step 9 | Go to DTC P0106 | ||||||||||||||||||||||||
9 |
Is the TP Indicated Angle parameter within the specified range? | 99-100% | Go to Step 10 | Go to DTC P1516 | ||||||||||||||||||||||||
10 |
Is the difference between the parameters at any time more than the specified value? | 2% | Go to DTC P2135 | Go to Step 11 | ||||||||||||||||||||||||
11 | Inspect the throttle body and the throttle valve for the following conditions:
Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 12 | ||||||||||||||||||||||||
Is the voltage within 1 volt of the specified value? | B+ | Go to Step 13 | Go to Step 20 | |||||||||||||||||||||||||
13 |
Important: All electrical components and accessories must be turned OFF.
Is the resistance less than the specified value? | 5 ohms | Go to Step 14 | Go to Step 21 | ||||||||||||||||||||||||
Is the voltage within the specified range? | 4.9-5.2 V | Go to Step 15 | Go to Step 17 | |||||||||||||||||||||||||
Is the MAF Sensor parameter within the specified range? | 4950-5025 Hz | Go to Step 16 | Go to Step 17 | |||||||||||||||||||||||||
|
Important: The J 38522 is able to overcome an abnormal resistance on the signal circuit of up to 1,150 ohms. The MAF sensor will not be able to overcome a resistance this high.
Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 18 | |||||||||||||||||||||||||
17 |
Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 19 | ||||||||||||||||||||||||
18 | Test for an intermittent and for a poor connection at the MAF/IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Repairing Connector Terminals. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 22 | ||||||||||||||||||||||||
19 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Repairing Connector Terminals. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 23 | ||||||||||||||||||||||||
20 | Repair the high resistance or the intermittent open in the MAF sensor ignition 1 voltage circuit. Refer to Wiring Repairs. Did you complete the repair? | -- | Go to Step 24 | -- | ||||||||||||||||||||||||
21 | Repair the high resistance or the intermittent open in the MAF sensor ground circuit. Refer to Wiring Repairs. Did you complete the repair? | -- | Go to Step 24 | -- | ||||||||||||||||||||||||
22 | Replace the MAF/IAT sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 24 | -- | ||||||||||||||||||||||||
23 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 24 | -- | ||||||||||||||||||||||||
24 |
Important: This diagnostic routine may have to be followed more than once.
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 25 | ||||||||||||||||||||||||
25 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||||||||||||||||
