GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The commanded throttle position (TP), based on the accelerator pedal position (APP), is compared to the actual throttle position. The TP values should be within a calibrated range of each other. The throttle actuator control (TAC) module monitors the commanded and the actual throttle position. If the TAC module detects that the commanded and the actual throttle positions are not within a calibrated range of each other or the TAC module, or the powertrain control module (PCM) cannot determine the throttle position, or if both TP sensors are invalid, a message is sent to the PCM across serial data and DTC P1516 is set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1516 Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance

Conditions for Running the DTC

    • The ignition is in the Crank or Run position.
    • The system is not in battery saver mode.
    • The ignition voltage is more than 5.23 volts.
    • The communication between the TAC module and the PCM must be valid.

Conditions for Setting the DTC

    • The TAC module detects that the commanded and the actual throttle positions are not within a calibrated range of each other.
        OR
    • The TAC module or the PCM cannot determine throttle position.
        OR
    • Both TP sensors are invalid.

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.

Diagnostic Aids

    • Inspect for mechanical conditions or for binding that may be temperature related. Components may not move freely in extreme heat or cold due to the presence of contaminants or ice formation.
    • If the condition is intermittent, refer to Intermittent Conditions .

Test Description

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

  1. Both TP sensor DTCs active at the same time will result in DTC P1516 also set. It is necessary to diagnose both sensor faults individually.

  2. A DTC U0107 set along with a sensor DTC may indicate a sensor fault. Refer to the sensor diagnostic table first.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views and Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

Is DTC P2108 also set?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 3

3

Are DTCs P0120 and P0220 both set?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 4

4

Is DTC U0107 set along with DTC P0120, P0220, P2120, or P2125?

--

Go to Step 6

Go to Step 5

5

Is DTC P1518 also set?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 8

6

Diagnose the appropriate sensor DTC first.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 7

7

  1. Turn OFF the ignition for 15 seconds.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the TP sensor 1 and TP sensor 2 angle parameter with a scan tool.
  4. Slowly depress the accelerator pedal to wide open throttle (WOT) and then slowly return the pedal to closed throttle.

Does the throttle position (TP) sensor 1 and TP sensor 2 angle increase to near the specified value as the pedal is depressed and decrease as the pedal is released?

100%

Go to Diagnostic Aids

Go to Step 8

8

Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement.

Did you complete the replacement?

--

Go to Step 9

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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

Important: Be aware that repairing 1 individual condition may correct more than 1 DTC.

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