GM Service Manual Online
For 1990-2009 cars only

Circuit Description

During Battery Saver Mode the TAC module determines if the throttle plate is returning to the correct de-energized position. If this fault is detected the TAC module sends a message to the PCM across serial data and this DTC is set.

Conditions for Running the DTC

    • DTC P1518 is not set.
    • The ignition is ON and the engine is OFF.
    • The ignition voltage is more than 8.5 volts.
    • Battery Saver Mode is active.

Conditions for Setting the DTC

The TAC module detects that the commanded and actual throttle positions are not within a calibrated range of each other.

Action Taken When the DTC Sets

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

Conditions for Clearing the MIL/DTC

    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • The history DTC clears after 40 malfunction free warm-up cycles.
    • The PCM receives a clear code command from the scan tool.

Diagnostic Aids

If you do not find any trouble, inspect for mechanical problems or 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.

The following could cause an intermittent condition:

Test Description

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

  1. When the TAC module detects a problem within the ETC System the PCM receives a message across serial data and more than one ETC System related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual problem may correct more than one DTC. Keep this in mind when reviewing captured DTC info.

DTC P1523 - Throttle Return Performance

Step

Action

Values

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Are any other DTCs set?

--

Diagnose these DTCs first

Go to Step 3

3

  1. Turn OFF the ignition for 15 seconds.
  2. Turn ON the ignition, with the engine OFF.
  3. Allow the pedal to rest at idle stop for 20 seconds.
  4. With a scan tool, observe the indicated Throttle Position parameter .

Does the scan tool indicate throttle position within the specified range?

10.8-23.2 %

Go to Step 6

Go to Step 4

4

Remove the throttle body/TAC assembly. Refer to Throttle Body Assembly Replacement .

Did you find any obstructions preventing the throttle blade from returning to the default position?

--

Go to Step 5

Go to Step 6

5

Remove the obstruction.

Did you complete the repair?

--

Go to Step 7

--

6

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

Did you complete the replacement?

--

Go to Step 7

--

7

  1. Use the scan tool in order to clear DTCs.
  2. Operate the vehicle within the Fail Records conditions.

Does the DTC reset?

--

Go to Step 2

Go to Step 8

8

Does the scan tool indicate any DTCs set that you have not diagnosed?

--

Go to applicable DTC

System OK