DTC P0068, P0101, P0106, P0121, or P1101

Engine Controls and Fuel - 5.3L L84 or 6.2L L87 | Diagnostic Information and Procedures | Document ID: 5839191 Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor DTC P0068 Throttle Body Air Flow Performance DTC P0101 Mass Airflow Sensor Performance DTC P0106 Manifold Absolute Pressure Sensor Performance DTC P0121 Throttle Position Sensor Performance DTC P1101 Intake Air Flow System Performance Circuit/System Description

	Component	Description
	B74 Manifold Absolute Pressure Sensor	The sensor is a capacitive pressure transducer. Electronics in the sensor convert pressure into an analog voltage signal. The sensor measures the pressure in the intake manifold between the throttle valve and the intake valves. When the engine is idling or decelerating, the sensor pressure should be low. When the engine is off or under wide-open throttle conditions the pressure should be the same or close to the barometric pressure.
	B75 Mass Airflow Sensor	The assembly has several functions: The mass air flow sensor is a hot film type sensor that measures the mass of air (not the volume) entering the engine. The signal varies with engine load and is displayed by the scan tool in Hertz (Hz) and grams per second (g/s). The component houses the following sensors: – Barometric Pressure Sensor – Barometric Pressure Sensor 2 – Intake Air Temperature Sensor – Intake Air Temperature Sensor 2 – Intake Air Humidity Sensor

Component	Description
K20 Engine Control Module	The control module contains a microprocessor used to process input data to control outputs. The control module controls a series of actuators to ensure optimal engine performance. The control module does this by reading values from a variety of sensors, interprets the data and adjusts the engine actuators accordingly.
Q38 Throttle Body	The component Q38 contains a contactless inductive position sensor. A fixed transmitter coil excites a movable rotor, which in turn induces a current in a fixed receiver coil. The current varies with the angle of the rotor. Electronics inside the sensor convert the current into digital data which is transmitted via a serial data circuit to the control module K20.

The ECM compares the measured mass air flow with the calculated air flow based on throttle position and the calculated air flow based on manifold absolute pressure. This DTC sets when the control module detects an inconsistency between the pressure sensors and cannot identify which sensor failed. Conditions for Running the DTC P0068 Engine Speed = Greater than 800 RPM Ignition Voltage = Greater than 6.4 V Frequency the DTC runs = Continuously — After the running conditions are met P0101, P0106, P0121, P1101 DTC P0102, P0103, P0107, P0108, P0111-P0114, P0116-P0119, P0128, P012C, P012D, P0335, P0336, P0401, P0402, P0404, P2227-P2230, P00E9, P00EA-P00EC, P042E, P010C, P010D, P111E, P14B6, U060F, U1346, U2011 = Not set DTC P0112, P0113, P0117, P0118, P0405, P0406, P00EA, P00EB, P14B6, P042E = Not pending ECT Sensor = −9 to 150°C (16 to 302°F) Engine Speed = 400 to 6800 RPM Intake Air Temperature Sensor = −20 to 125°C (−4 to 257°F) Frequency the DTC runs = Continuously — After the running conditions are met — For greater than 1 s Conditions for Setting the DTC P0068, P1101 The following scan tool parameters are not within a calibrated range of the calculated air flow, which is based on throttle position: Mass Airflow Sensor Manifold Absolute Pressure Sensor P0101 Condition 1 The ratio between the measured and estimated mass air flow is too low — For greater than 1 s Condition 2 The ratio between the measured and estimated mass air flow is too high — For greater than 1 s P0106, P0121 Signal Stuck In Range or ≠ Calculated Air Flow — For greater than 1 s Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type A DTC — Exceptions listed below DTC P0101, P0106, P0121, P1101 = Type B DTC Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type A DTC — Exceptions listed below DTC P0101, P0106, P0121, P1101 = Type B DTC Reference Information Schematic Reference Engine Controls Schematics Connector End View Reference Master Electrical Component List DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References Special Tools GE-52250 Variable Pressure Leak Detector Equivalent regional tools: Special Tools Circuit/System Verification

Ignition » On / Vehicle » In Service Mode
Verify there are no DTCs set related to the following component/system: B74 Manifold Absolute Pressure Sensor B75 Mass Airflow Sensor 5V Reference Circuit Throttle Position Sensor @ Q38 Throttle Body ⇒ If a related DTC is set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If a related DTC is not set
Verify the scan tool parameter: Throttle Body Idle Air Flow Compensation = Less than 90% ⇒ If 90% or greater Refer to: Throttle Body Cleaning ⇓ If less than 90%
Perform the scan tool control function: Throttle Sweep » Start Verify the scan tool parameter: Throttle Position Sensor and Sensor 2 = Agree ⇒ If not the specified state Refer to: DTC P0122, P0123, P0222, P0223, P2135, U0606, or U0607 ⇓ If the specified state
Verify the scan tool parameter: Manifold Absolute Pressure Sensor = The value should be within the range listed in the table: Altitude Versus Barometric Pressure ⇒ If not in the specified range Refer to: DTC P0107 or P0108 ⇓ If in the specified range
Verify the tool is available: GE-52250 Variable Pressure Leak Detector ⇒ If the tool is not available Refer to step 8 ⇓ If the tool is available
Perform the following procedure/test: Component/System Leak Test Verify the procedure/test passes. ⇒ If the procedure/test does not pass Repair or replace as necessary ⇓ If the procedure/test passes
Verify the following conditions do not exist: B74 Manifold Absolute Pressure Sensor — Visible Damage B75 Mass Airflow Sensor — Contamination of the measuring element / Visible Damage / Water intrusion Q38 Throttle Body – Coking / Loose Clamps / Visible Damage – Restricted — Moisture / Ice Air Cleaner Element — Dirty / Restricted Catalytic Converter & Exhaust System — Blocked / Leaking / Restricted / Visible Damage » Refer to: Symptoms - Engine Exhaust Intake Air Duct — Collapsed / Restricted / Visible Damage Intake Manifold — Restricted / Visible Damage Positive Crankcase Ventilation System — Restricted — Moisture / Ice ⇒ If a condition exists Repair or replace the components as necessary. ⇓ If no condition exists
Engine » Idling — At normal operating temperature
Verify the scan tool parameter: Manifold Absolute Pressure Sensor = 26 to 52 kPa (3.8 to 7.5 PSI) @ Idle Speed Manifold Absolute Pressure Sensor = The value should change with accelerator pedal input. ⇒ If not between 26 and 52 kPa (3.8 and 7.5 PSI) or does not change Refer to: DTC P0107 or P0108 ⇓ If between 26 and 52 kPa (3.8 and 7.5 PSI) and changes
Increase the engine speed slowly to 3k RPM and then back to idle.
Perform the scan tool function: Review Stored Data
Observe the scan tool parameter frame by frame with a scan tool: Mass Airflow Sensor = The value should not spike or drop out. ⇒ If the value spikes or drops out Refer to: DTC P0102, P0103, U060F, or U1319 ⇓ If the value does not spike or drop out
Verify the following conditions do not exist: Engine — Mechanical Condition

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. Verify the DTC does not set. ⇒ If the DTC sets Repeat the procedure starting at step 1 ⇓ If the DTC is not set
All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification