For 1990-2009 cars

### Circuit Description

The engine control module (ECM) opens the throttle valve by applying a pulse width modulation voltage (PWM) to the throttle actuator control motor. The ECM reverses the polarity on the throttle actuator control motor control circuits in order to close the throttle valve. The ECM increases the pulse width as necessary to open the throttle valve. The ECM monitors throttle position (TP) sensors 1 and 2 to determine the actual throttle valve position. If the ECM detects that the output driver for the throttle actuator control (TAC) motor does not deactivate when commanded OFF, this DTC sets.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2100 Throttle Actuator Control (TAC) Motor Control Circuit

### Conditions for Running the DTC

• | Before the ECM can report DTC P2100 failed, DTC P2101 must run and pass.

• | The ignition is ON or the engine is operating.

• | DTC P2100 runs continuously once the above conditions are met for more than 1 second.

### Conditions for Setting the DTC

• | The ECM detects the output driver for the TAC motor does not deactivate when commanded OFF.

• | The condition exists for less than 4 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/Failure Records.

### Conditions for Clearing the MIL/DTC

• | The control module turns OFF the malfunction indicator lamp (MIL) after 4 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

• | Use the J 35616-A/BT-8637 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

• | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Front of Vehicle/Engine Compartment Component Views.

• | Inspect for a condition in which the throttle valve may have been held open. For example, ice may have formed in the throttle bore causing the throttle valve not to close. Observe the Freeze Frame/Failure Records.

• | The throttle valve is spring loaded to a slightly open position. The throttle valve should be open approximately 3-5 percent. This is referred to as the rest position.

• | The throttle valve should not be completely closed or open any more than a specified amount.

• | The throttle valve should move open and to the closed position without binding under the normal spring pressure.

• | The throttle should NOT be free to move open or closed without spring pressure.

• | The scan tool has the ability to operate the throttle control system using the TP function located in the TAC System menu. This function operates the throttle valve through the entire range in order to determine if the TAC system operates correctly.

• | For an intermittent condition, refer to Intermittent Conditions.

### Test Description

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

1. This step determines if the condition exists. A TP sensor DTC may cause this DTC to set.

2. Depending on the condition, DTC P0638, P2100, P2101, and/or P2119 may set individually or together.

3. When the ignition is turned ON, the ECM operates the throttle actuator control motor to verify the integrity of the system prior to start-up. This can be seen by the momentary flash of the test lamp as the ignition is turned ON.

Step | Action | Value | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Component Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn ON the ignition, with the engine OFF.
2. Clear the DTCs with a scan tool.
3. Start the engine.
4. Perform the following tests:

• | Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times.

• | Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times.

5. Observe the DTC information with a scan tool.

Did DTC P0121, P0122, P0123, P0221, P0222, or P0223 fail this ignition?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 3

3 | Did DTC P0638, P2100, P2101, and/or P2119 fail this ignition? | -- | Go to Step 5 | Go to Step 4
4 |

1. Observe the Freeze Frame/Failure Records for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. 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 5

Go to Diagnostic Aids

5 |

1. Turn OFF the engine.
2. Turn ON the ignition, with the engine OFF.
3. Observe the TP sensor 1 voltage parameter with a scan tool.

Is the voltage within the specified range?

0.40-0.80 V

Go to Step 6

Go to DTC P0121

6 | Observe the TP sensor 2 voltage parameter with a scan tool. Is the voltage within the specified range? | 4.7-4.1 V | Go to Step 7 | Go to DTC P0221
7 |

Caution: Refer to Disengaging Connectors Caution in the Preface section.

Note: Disconnecting the throttle body harness connector causes additional DTCs to set.

1. Disconnect the throttle body harness connector. Refer to Throttle Body Assembly Replacement.
2. Turn ON the ignition, with the engine OFF.
3. Measure the voltage of the throttle actuator control (TAC) motor control 1 and TAC motor control 2 circuits of the throttle actuator control motor with a DMM connected to the engine control module (ECM) housing.

Is the voltage within the specified range for both circuits?

2-4 V

Go to Step 8

Go to Step 9

8 |

1. Turn OFF the ignition.
2. Connect the J 34730-405 Injector Test Lamp between the TAC motor control 1 and TAC motor control 2 circuit of the throttle body harness connector.

Note: The test lamp intensity should be bright. Compare to another vehicle.

3. Turn On the ignition for about 5 seconds and then turn OFF the ignition while you observe the test lamp. Repeat this procedure, as necessary.

Does the test lamp turn ON and then OFF each time the ignition is cycled?

--

Go to Step 12

Go to Step 11

9 | Is the voltage less than the specified value? | 2 V | Go to Step 10 | Go to Step 14
10 | Test the TAC motor control circuit that measured below the specified value for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 13
11 |

1. Turn OFF the ignition.
2. Disconnect the ECM.
3. Test for continuity between the TAC motor control 1 and TAC motor control 2 circuit of the throttle body harness connector.

Is there continuity?

--

Go to Step 15

Go to Step 13

12 | Test for shorted terminals and for poor connections at the throttle body connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 16
13 | Test for shorted terminals and for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 17
14 | Repair the appropriate TAC motor control circuit for a short to voltage. Refer to Wiring Repairs. Did you complete the repair? | -- | Go to Step 18 | --
15 | Repair the short between the TAC motor control circuits 1 and 2. Refer to Wiring Repairs. Did you complete the repair? | -- | Go to Step 18 | --
16 | Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement. Did you complete the replacement? | -- | Go to Step 18 | --
17 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 18 | --
18 |

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. 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 19

19 | 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