Circuit Description
The powertrain control module (PCM) uses the throttle position (TP), barometric pressure (BARO), intake air temperature (IAT), and engine RPM in order to calculate the predicted mass airflow rate. The PCM compares the predicted mass air flow (MAF) value to the actual mass airflow value and the speed density calculation in order to verify the proper throttle operation. If the PCM detects that the difference between the actual air flow (MAF) and the speed density calculated air flow is greater than expected, DTC P0068 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0068 MAF/MAP - Throttle Position Correlation
Conditions for Running the DTC
| • | DTCs P0601, P0602, P0604, P0606, P1516, P2101, P2108, U0107 are not set. |
| • | DTCs P0120, P0220, and P2135 are not set at the same time or DTCs P0120 and P0220 are not set at the same time. |
| • | The engine operates longer than 1 second. |
| • | The engine speed is more than 500 RPM. |
| • | DTC P0068 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
| • | The PCM detects that the difference between the actual airflow (MAF) and the speed density calculated airflow is greater than expected. |
| • | The above condition is met for more than 1.88 seconds. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records. |
| • | The control module commands the 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. |
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
| • | Inspect the throttle blade for being broken, bent, or missing. |
| • | Inspect the TP sensor for proper installation. A sensor that is mis-aligned could set this DTC. |
| • | Inspect the TAC module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing. |
| • | Physically and visually inspect the throttle body assembly, and correct any problems that you observe. Manually move the throttle blade from closed to wide open throttle (WOT). You should not need to use excessive force. The throttle blade should move smoothly through the full range and should return to a slightly open position on its own. |
| • | When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | |||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||
2 | Is DTC P0101, P0102, P0103, P0107, P0108, P0112, P0113, P1111, or P1112 set? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 3 | ||||||||
3 |
Caution: Turn OFF the ignition before inserting fingers into the throttle bore. Unexpected movement of the throttle blade could cause personal injury. Important: If any of the conditions listed below exist, replace the throttle body assembly. Refer to Throttle Body Assembly Replacement . Inspect the throttle body for the following conditions:
Did you find and correct the condition? | Go to Step 4 | Go to Diagnostic Aids | ||||||||
4 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 5 | ||||||||
Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | |||||||||
