Test Description

The numbers below refer to the step numbers on the diagnostic table.

5: This step will determine if the MAP sensor voltage is within the proper range at idle.
6: This step will determine if the MAP sensor responds properly to the change in manifold pressure.
9: When the PCM detects a condition within the throttle actuator control (TAC) system, other DTCs may set due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Keep this in mind when reviewing captured DTC info.

DTC P0121

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
2	Are DTCs P0120, P0220, P1516, P2101, P2119, P2135 or P2176 also set?	-	Go to Diagnostic Trouble Code (DTC) List - Vehicle	Go to Step 3
3	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition. Start the engine. 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. Did the DTC fail this ignition?	-	Go to Step 4	Go to Testing for Intermittent Conditions and Poor Connections
4	Inspect for the following conditions: Vacuum hoses for splits, kinks and proper 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 Did you find and correct the condition?	-	Go to Step 9	Go to Step 5
5	Allow the engine to reach operating temperature. Turn OFF all accessories. Observe the MAP sensor kPa parameter with a scan tool. Is the manifold absolute pressure (MAP) sensor kPa within the specified range?	19-42 kPa	Go to Step 6	Go to DTC P0106
6	Idle the engine. Observe the MAP sensor kPa parameter with a scan tool. Increase the engine speed slowly and then back to idle. 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	Idle the engine. Take a snapshot of the Engine Data while performing the following action: Increase the engine speed slowly to 3,000 RPM, then back to idle. Exit from the snapshot and review the data. Observe the MAF sensor parameter frame by frame with a scan tool. Refer to Scan Tool Snapshot Procedure . Does the MAF sensor g/s change smoothly and gradually as the engine speed is increased and is returned to idle?	-	Go to Step 8	Go to DTC P0101 or P1101
8	CAUTION: Turn OFF the ignition before inserting fingers into the throttle bore. Unexpected movement of the throttle blade could cause personal injury. Inspect the throttle body for the following conditions while modulating the throttle using the scan tool: Loose or damaged throttle blade Broken throttle shaft Drive mechanism damage If any of these conditions exist, replace the throttle body assembly. Refer to Throttle Body Assembly Replacement . Did you find and correct the condition?	-	Go to Step 9	Go to Testing for Intermittent Conditions and Poor Connections
9	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. 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. 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	System OK