GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2007 🢒 Lumina VE 🢒 Engine 🢒 Engine Controls and Fuel - 6.0L 🢒 DTC P0068 or P0121

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category

DTC Descriptors

DTC P0068: MAP/MAF - Throttle Position Correlation

DTC P0121: Throttle Position Sensor Circuit Range/Performance

Circuit/System Description

The engine control module (ECM) uses the following information to calculate an expected airflow rate:

    • The throttle position sensor (TP).
    • The manifold absolute pressure (MAP).
    • The intake air temperature (IAT).
    • The engine RPM.

Conditions for Running the DTC

P0068

    • DTCs P0641, P0651, P1516, P2101 or P2119 are not set.
    • The engine is running.
    • DTC P0068 runs continuously when the above conditions are met.

P0121

    • DTCs P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0128, P0315, P0335 or P0336 are not set.
    • The engine speed is more than 450 RPM.
    • DTC P0121 run 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.

P0121

The predicted air flow and the predicted MAP combined are outside a calibrated range for more than 3 seconds.

Action Taken when the DTC Sets

DTCs P0068 or P0121 are type A DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0068 or P0121 are type A DTCs.

Reference Information

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs
    •  Heated Oxygen Sensor Wiring Repairs

Scan Tool Reference

Control Module References

Circuit/System Testing
  1. Inspect for the following conditions:
    2. • Vacuum hoses for splits, kinks and correct connections as shown on Vehicle Emission Control Information label.
    • Inspect thoroughly for any type of leak or restriction.
    • Air leaks at throttle body mounting area and intake manifold sealing surfaces.
  2. Inspect the throttle body for the following conditions:
    3. • Loose or damaged throttle blade.
    • Broken throttle shaft.
    • Any throttle body damage.
    ⇒If any of these conditions exist, replace the throttle body assembly.
  3. Allow the engine to reach normal operating temperature. Using a scan tool observe the MAP and MAF sensor parameters.
  4. Take a snapshot of the engine data list while performing the actions listed below.
    5. • Idle the engine.
    • Increase the engine speed slowly to 3,000 RPM, then back to idle.
    • Exit from the snapshot and review the data.
    • Observe the MAP/MAF/TP sensor parameters frame by frame. The MAP/MAF/TP sensor parameters should change smoothly and gradually as the engine speed is increased and is returned to idle.
         ⇒If the MAP/MAF/TP sensor parameters do not change smoothly and gradually as the engine speed is increased and is returned to idle, identify the sensor at fault and replace the appropriate sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Throttle Body Assembly Replacement
    •  Engine Control Module Replacement for engine control module replacement, setup and programming.