Diagnostic Instructions
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). |
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
Scan Tool Reference
Control Module References
Circuit/System Testing
- Inspect for the following conditions:
• | 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. |
- Inspect the throttle body for the following conditions:
• | Loose or damaged throttle blade. |
• | Broken throttle shaft. |
• | Any throttle body damage. |
⇒ | If any of these conditions exist, replace the throttle body assembly. |
- Allow the engine to reach normal operating temperature. Using a scan tool
observe the MAP and MAF sensor parameters.
- Take a snapshot of the engine data list while performing the actions
listed below.
• | 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.