For 1990-2009 cars

### Circuit Description

The Throttle Actuator Control (TAC) System determines the drivers intent and then calculates the appropriate throttle response. The TAC system achieves throttle positioning by providing a pulse width modulated voltage to the TAC motor. The powertrain control module (PCM) is the control center for the TAC system. Ignition 1 voltage is supplied on 2 separate circuits to the PCM. If the PCM detects a voltage difference between the 2 circuits, DTC P1682 sets.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1682 Ignition 1 Switch Circuit 2

### Conditions for Running the DTC

• | The ignition is in Unlock, Accessory, Run, or Crank mode.

• | DTC P1682 runs continuously when the above condition is met.

### Conditions for Setting the DTC

The ignition 1 voltage is less than 10 volts for more than 10 seconds.

### Action Taken When the DTC Sets

• | The control module stores the DTC information into memory when the diagnostic runs and fails.

• | The malfunction indicator lamp (MIL) will not illuminate.

• | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

• | The driver information center, if equipped, may display a message.

### Conditions for Clearing the DTC

• | 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 non-emission related diagnostic.

• | Clear the DTC with a scan tool.

### Test Description

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

1. This step determines if there is voltage present to the ECM fuse.

2. This step determines if voltage is present at the PCM.

3. This step determines if the PCM ignition 1 voltage circuit is shorted to ground.

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

1. Observe the Freeze Frame/Failure Records for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF for 10 seconds.

Does the DTC fail this ignition?

--

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3 | With a test lamp connected to ground, probe both sides of the 15-amp ECM/ETC fuse. Does the test lamp illuminate on both sides of the fuse? | -- | Go to Step 5 | Go to Step 4
4 | Does the test lamp illuminate on one side of the fuse? | -- | Go to Step 6 | Go to Powertrain Relay Diagnosis
5 |

1. Turn OFF the ignition.
2. Disconnect the powertrain control module (PCM).
3. Test the ignition 1 voltage circuit that is supplied by the ECM/ETC fuse for an open or for a high resistance. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 7

6 |

1. Turn OFF the ignition.
2. Disconnect the PCM.
3. Test the ECM/ETC ignition 1 voltage circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs.
4. Replace the fuse if necessary.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 7

7 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8
8 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 9 | --
9 |

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 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