For 1990-2009 cars

### Circuit Description

The throttle actuator control (TAC) system uses two accelerator pedal position (APP) sensors to monitor the pedal position. Two processors are also used to monitor the TAC system data. The Powertrain control module (PCM) performs an intrusive test in order to detect that the APP signals are not shorted together. The PCM accomplishes this by pulling the APP sensor 2 low momentarily and looking for sensor 1 to also be low. The TAC system also performs this test on the throttle position (TP) sensors. This diagnostic monitors the transistor used to pull one pedal and one throttle sensor to ground simultaneously. Additionally, Both processors monitor each other's data to verify that the indicated APP calculation is correct.

If the transistor does not toggle within a calibrated period, or the indicated APP calculation is incorrect , DTC P1680 sets

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1680 Control Module Accelerator Pedal Position (APP) System Performance

### Conditions for Running the DTC

• | The system voltage is more than 5.23 volts.

• | The ignition is in Unlock/Accessory or Run position.

• | DTCs P0601, P0602, P0604, P0606, P0607, or P1621 are not set.

• | DTC P1680 runs continuously when the above conditions are met.

### Conditions for Setting the DTC

• | The APP sensor 2 voltage is more than 1.75 volts for more than 0.3 second during the intrusive test.

| OR

• | The APP sensor calculations in the main processor differ from the motor control processor by more than 0.142 volt for more than 1.2 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.

### Test Description

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

1. A DTC P0602 indicates that the PCM is not programmed.

2. Resistance is measured at the pedal assembly because a pedal resistance that is lower than the specified value will set this DTC

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Is DTC P0602 set? | -- | Go to Step 3 | Go to Step 5
3 | Program the powertrain control module (PCM). Refer to Service Programming System (SPS) . Does DTC P0602 reset? | -- | Go to Step 4 | Go to Step 8
4 |

1. Ensure that all tool connections are secure.
2. Ensure that the programming equipment is operating correctly.
3. Ensure that the correct software/calibration package is used.
4. Attempt to program the PCM. Refer to Service Programming System (SPS) .

Does DTC P0602 reset?

--

Go to Step 7

Go to Step 8

5 |

1. Turn OFF the ignition.
2. Disconnect the accelerator pedal connector
3. Ensure that the pedal is at the rest position.
4. Measure the resistance from the 5-volt reference of the accelerator pedal assembly to the accelerator pedal position (APP) sensor 2 signal of the accelerator pedal assembly with a DMM. Refer to Circuit Testing .

Is the resistance less than the specified value?

450 ohms

Go to Step 6

Go to Step 7

6 | Replace the accelerator pedal assembly. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 8 | --
7 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 8 | --
8 |

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

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 9

9 | 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