The powertrain control module (PCM) 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 mass air flow (MAF) |
• | The engine RPM |
If the PCM detects the airflow rate is more than expected, DTC P0121 sets.
• | DTCs P0641, P0651, P1516, P2101, P2119, P2176 are not set. |
• | The engine is running and the engine speed is more than 600 RPM. |
The PCM detects that the calculated airflow rate is more than expected.
• | 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. |
• | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed. |
• | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
• | The DTC can be cleared by using a scan tool. |
The numbers below refer to the step numbers on the diagnostic table.
This step will determine if the MAP sensor voltage is within the proper range at idle.
This step will determine if the MAP sensor responds properly to the change in manifold pressure.
When the PCM detects a condition within the ETC system other DTCs may set due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Keep this in mind when reviewing captured DTC info.
Step | Action | Values | 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 | Are DTCs P0120, P0220, P1516, P1523, P2101, P2135 or P2176 also set? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 3 | ||||||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||||||
4 | Inspect for the following conditions:
Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 5 | ||||||||
Is the MAP sensor voltage within the specified range? | 0.8-4 V | Go to Step 6 | Go to DTC P0106 | |||||||||
Does the MAP sensor kPa change smoothly and gradually as engine speed is increased and returned to idle? | -- | Go to Step 7 | Go to DTC P0106 | |||||||||
7 |
Does the MAP sensor kPa change smoothly and gradually as the engine speed is increased and is returned to idle? | -- | Go to Step 8 | Go to DTC P0101 | ||||||||
8 |
Caution: Turn OFF the ignition before inserting fingers into the throttle bore. Unexpected movement of the throttle blade could cause personal injury.
Did you find and correct the condition? | -- | Go to Step 9 | Go to Intermittent Conditions | ||||||||
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 10 | |||||||||
10 | 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 |