GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Generic 🢒 2003 🢒 Unit Repair 🢒 Engine 🢒 Engine Controls - 4.8L, 5.3L, and 6.0L 🢒 DTC P2125

Circuit Description

The accelerator pedal position (APP) sensor 2 is a potentiometer type sensor with the following circuits:

    • A 5-volt reference circuit
    • A low reference circuit
    • A signal circuit

The control module provides the APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensor then provides the control module a signal voltage proportional to pedal movement. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed. When the control module detects that the APP sensor 2 signal or the APP sensor 5-volt reference voltage is outside the predetermined range, this DTC sets.

Conditions for Running the DTC
    • DTCs  P0601, P0602, P0606, P1518, or P2108 are not set.
    • The ignition switch is in the crank or run position.
    • The ignition voltage is more than 5.23 volts.

Conditions for Setting the DTC
    • The APP sensor 2 voltage is less than 0.24 volt or more than 4.49 volts.
        OR
    • The 5-volt reference is less than 4.54 volts or more than 5.21 volts.
    • One of the above conditions is present for more than 1 second.

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.
    • If one or more APP sensor DTCs are set, the following occurs:
       - The control module commands Reduced Engine Power mode.
       - The APP indicated angle is limited to a predetermined value to limit the amount of throttle control.
       - OR
       - The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle.
       - The message center displays Reduced Engine Power.

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.

Diagnostic Aids
    • Inspect the throttle actuator control (TAC) module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
    • When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
    • For an intermittent, refer to Intermittent Conditions .

Test Description

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

  1. The throttle position (TP) sensor 2 and the APP sensor 2 share a common 5-volt reference source. Diagnose DTC P0220 first if P0220 is also set.

    2.

  2. This test determines whether or not the TAC module can recognize a change in signal voltage.

    3.

  3. There are 2 separate 5-volt reference sources within the TAC module. The TP sensor 1 and the APP sensor 1 share one 5-volt reference source. The TP sensor 2 and the APP sensor 2 share another common 5-volt reference source. This test determines whether the signal circuit is shorted to any one of the 5-volt reference circuits. If a short exists, the corresponding sensor voltage will be pulled low.

    4.

  4. The previous step found the signal circuit and a 5-volt reference circuit shorted together. This test isolates whether the short is in the harness or within the TAC module.

    5.

  5. When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.

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-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: If DTCs P0220 or P1518 is also set, refer to Diagnostic Trouble Code (DTC) List and diagnose the applicable DTC first.

  1. Turn ON the ignition, with the engine OFF, and with your foot OFF of the accelerator pedal.
  2. Observe the accelerator pedal position (APP) sensor 2 voltage parameter with a scan tool.

Does the scan tool indicate APP sensor 2 voltage within the specified values?

0.24-2.24 V

Go to Step 3

Go to Step 6

3

Fully depress the accelerator pedal to the wide open throttle (WOT) position.

Does the scan tool indicate APP sensor 2 voltage within the specified values?

0.24-4.49 V

Go to Step 4

Go to Step 6

4
  1. Turn OFF the ignition for 15 seconds.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe DTC info with a scan tool.
  4. Lightly touch and move the related engine wiring harnesses and connectors for the APP sensor while observing the DTC status.
  5. If the scan tool indicates this DTC failed this ignition during the above test, repair the intermittent condition as necessary. Refer to Wiring Repairs and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 5

5

Slowly depress the accelerator pedal to WOT, then slowly return the pedal to closed throttle while observing the DTC status.

Did the scan tool indicate this DTC failed this ignition during the above test?

--

Go to Step 21

Go to Diagnostic Aids

6
  1. Disconnect the APP sensor harness connector.
  2. Test the APP sensor 2 signal circuit for voltage with a DMM.

Does the DMM indicate APP sensor 2 signal voltage within the specified values?

3.94-6.06 V

Go to Step 11

Go to Step 7

7
  1. Turn OFF the ignition.
  2. Disconnect the throttle actuator control (TAC) module harness connector containing the APP sensor circuits.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the APP sensor 2 signal circuit for a short to voltage with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 8

8

Test the APP sensor 2 signal circuit for an open or high resistance with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 9

9

Test the APP sensor 2 signal circuit for a short to ground with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 10

10

Test for a short between the APP sensor 2 signal circuit and all other TAC module circuits with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 23

11

Test the APP sensor 2, 5-volt reference circuit for voltage with a DMM.

Does the DMM indicate voltage within the specified values?

4.54-5.21 V

Go to Step 16

Go to Step 12

12
  1. Turn OFF the ignition.
  2. Disconnect the TAC module harness connector containing the APP sensor circuits.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the APP sensor 2, 5-volt reference circuit for a short to voltage with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 13

13

Test the APP sensor 2, 5-volt reference circuit for an open or high resistance with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 14

14

Test the APP sensor 2, 5-volt reference circuit for a short to ground with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 15

15

Test for a short between the APP sensor 2, 5-volt reference circuit and all other TAC module circuits with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 23

16

Measure resistance With a DMM connected between the APP sensor 2 low reference circuit and the APP sensor 1 low reference circuit.

Does the DMM indicate resistance within the specified values?

0-5 ohms

Go to Step 18

Go to Step 17

17
  1. Turn OFF the ignition.
  2. Disconnect the TAC module harness connector containing the APP sensor circuits.
  3. Test the APP sensor 2 low reference circuit for an open or high resistance with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 23

18

  1. Connect a fused jumper between the APP sensor 2 signal circuit and the APP sensor 2 low reference circuit at the APP sensor harness connector.
  2. Observe the APP sensor 2 voltage parameter with a scan tool.

Does the scan tool indicate APP sensor 2 voltage at the specified value?

0 V

Go to Step 19

Go to Step 23

19

  1. Observe the APP sensor 1, APP sensor 3 and TP sensor 2 voltage parameters with a scan tool.
  2. Connect a fused jumper between the APP sensor 2 signal circuit and the APP sensor 2 low reference circuit at the APP sensor harness connector.

Did the scan tool indicate a change in voltage in any of the parameters observed during the above test?

--

Go to Step 20

Go to Step 21

20

  1. Turn OFF the ignition.
  2. Disconnect the TAC module harness connectors.
  3. Test for a short between the APP sensor 2 signal circuit and all other TAC module circuits with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 23

21

Inspect for poor connections at the harness connector of the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 22

22

Replace the APP sensor assembly. Refer to Accelerator Pedal Position Sensor Replacement .

Did you complete the replacement?

--

Go to Step 25

--

23

Inspect for poor connections at the harness connector of the TAC module . Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 24

24

Replace the TAC module. Refer to Electronic Throttle Actuator Control Module Replacement .

Did you complete the replacement?

--

Go to Step 25

--

25
  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 26

26

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK