P0068
DTC P0068 or P1101 (Without Supercharger)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P0068
- Throttle Body Air Flow Performance
DTC P1101
- Intake Air Flow System Performance
Circuit/System Description
The engine control module (ECM) uses the following information to calculate an expected airflow rate:
* The throttle position (TP)
* The barometric pressure (BARO)
* The manifold absolute pressure (MAP)
* The intake air temperature (IAT)
* The engine RPM
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 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.
Conditions for Running the DTCs
P0068
* The engine speed is above 800 RPM.
* The ignition voltage is at least 6 V.
* This DTC runs continuously when the above conditions are met.
P1101
* DTCs P0102, P0103, P0107, P0108, P0111, P0112, P0113, P0116, P0117, P0118, P0128, P0335, or P0336 are not set.
* The engine speed is between 450-5,750 RPM.
* The intake air temperature is between -20 and +125°C (-4 and +257°F).
* The engine coolant temperature is between -20 and +125°C (-4 and +257°F).
* This DTC runs continuously when the above conditions are met.
Conditions for Setting the DTC
P0068
The ECM detects that the throttle position and the indicated engine load do not correspond with the expected load and throttle position for less than 1 second.
P1101
The engine control module (ECM) detects that the actual measured airflow from the MAF, MAP, and TP sensors is not within range of the calculated airflow that is derived from the system of models for more than 0.5 s.
Action Taken When the DTCs Set
P0068
* DTC P0068 is a Type A DTC.
* The control module commands the throttle actuator control (TAC) system to operate in the Reduced Engine Power mode.
* A message center or an indicator displays Reduced Engine Power.
* Under certain conditions the control module commands the engine OFF.
P1101
DTC P1101 is a Type B DTC.
Conditions for Clearing the MIL/DTCs
* DTC P0068 is a Type A DTC.
* DTC P1101 is a Type B DTC.
Diagnostic Aids
* A steady or intermittent high resistance of 15 ohms or greater on the ignition voltage circuit will cause the MAF sensor signal to be increased by as much as 60 g/s. To pinpoint this condition perform a voltage drop test on the circuit.
* Any type of contamination on the MAF sensor heating elements will degrade the proper operation of the sensor. Certain types of contaminants act as a heat insulator, which will impair the response of the sensor to airflow changes. Water or snow can create the opposite effect, and cause the signal to increase rapidly.
* Depending on the current ambient temperature, and the vehicle operating conditions, a MAF sensor signal circuit that is shorted to the IAT signal circuit will increase or decrease the MAF sensor signal that is interpreted by the ECM. Additionally it may cause a rapid fluctuation in the IAT Sensor parameter.
* 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. Refer to Temperature Versus Resistance Temperature Versus Resistance
* Certain aftermarket air filters may cause this DTC to set.
* Certain aftermarket air induction systems may cause this DTC to set.
* Modifications to the air induction system may cause this DTC to set.
Reference Information
Schematic Reference
Engine Controls Schematics (LS3) [1][2]Electrical DiagramsEngine Controls Schematics (LS7) [1][2]Electrical DiagramsEngine Controls Schematics (LS9) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views 5 Bow Lowered Switch (CM7)
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References
Circuit/System Verification
1. Ignition ON.
2. Verify the scan tool TB Idle Airflow Compensation parameter is less than 90 %.
• 90 % or greater
Refer to Throttle Body Cleaning Procedures.
• If less than 90 %
3. Verify the scan tool TP Sensors 1 and 2 Agree/Disagree parameter displays Agree while performing the Throttle Sweep Test with a scan tool.
• If Disagree
Refer to DTC P0120-P0123, P0220, P0222, P0223, or P2135 (Without Supercharger) DTC P0120-P0123, P0220, P0222, P0223, or P2135 (Supercharger) for further diagnosis.
• If Agree
4. Determine the current vehicle testing altitude.
5. Verify the scan tool MAP Sensor pressure parameter is within the range specified in the Altitude Versus Barometric Pressure Altitude Versus Barometric Pressure table.
• The MAP Sensor pressure is not in range
Refer to DTC P0106 (Without Supercharger) DTC P0106 (Supercharger) for further diagnosis.
• The MAP Sensor pressure is within range
6. Engine idling, verify the scan tool MAP Sensor pressure parameter is between 26-52 kPa (3.8-7.5 psi) and changes with accelerator pedal input.
• If not between 26-52 kPa (3.8-7.5 psi) or does not change
Refer to DTC P0106 (Without Supercharger) DTC P0106 (Supercharger) for further diagnosis.
• If between 26-52 kPa (3.8-7.5 psi) and changes
7. Verify the scan tool MAF Sensor g/s parameter changes smoothly and gradually as the engine speed is increased and decreased while performing the actions listed below.
1. Engine idling
2. Perform the scan tool snapshot function.
3. Increase the engine speed slowly to 3,000 RPM and then back to idle.
4. Exit from the scan tool snapshot and review the data.
5. Observe the MAF Sensor parameter frame by frame with a scan tool.
• The MAF Sensor parameter does not change smoothly and gradually
Refer to DTC P0101 (Without Supercharger) DTC P0101 (Supercharger) for further diagnosis.
• The MAF Sensor parameter changes smoothly and gradually
8. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
9. Verify a DTC does not set.
• If any DTC sets
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
• If no DTCs set
10. All OK
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.