GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The throttle position (TP) sensor 1 is a potentiometer type sensor with three circuits:

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

The TP sensor is used to determine the throttle plate angle for various engine management systems. The control module provides the TP sensor a 5-volt reference circuit and a low reference circuit. The TP sensor then provides the control module a signal voltage proportional to throttle plate movement. TP sensor 1 signal voltage is low at closed throttle and increases as the throttle opens. When the control module detects that the TP sensor 1 signal or TP sensor 5-volt reference voltage is outside the predetermined range, this DTC sets.

Conditions for Running the DTC

    • DTCs P1518 or P2108 are not set.
    • The ignition switch is in the crank or run position.
    • The ignition voltage more than 5.23 volts.

Conditions for Setting the DTC

    • The TP sensor 1 signal voltage is less than 0.37 volt or more than 4.51 volts.
    • The above condition is present for more than 1 second.

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 the throttle actuator control (TAC) module connectors for signs of water intrusion. When this occurs, multiple DTCs could be set with no circuit or component conditions found during diagnostic testing.
    • When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
    • If this DTC is determined to be intermittent, refer to Intermittent Conditions .

Test Description

The number below refers to the step number on the diagnostic table.

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

Step

Action

Values

Yes

No

Schematic References: Engine Controls Schematics

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

  1. Turn OFF the ignition.
  2. Remove the air inlet duct from the throttle body.
  3. Disconnect the throttle body harness connector.
  4. Connect jumper wires between the throttle position (TP) sensor 1 terminals of the throttle body harness connector and the corresponding TP sensor 1 terminals of the throttle body.
  5. Turn ON the ignition, with the engine OFF.
  6. Close the throttle blade by hand.
  7. Observe the TP sensor 1 voltage with a scan tool.

Is the TP sensor 1 voltage within the specified range?

0.37-0.71 V

Go to Step 5

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Connect jumper wires between the TP sensor 2 terminals of the throttle body harness connector and the corresponding TP sensor 2 terminals of the throttle body.
  3. Turn ON the ignition, with the engine OFF.
  4. Close the throttle blade by hand.
  5. Observe the TP sensor 2 voltage with a scan tool.

Is the TP sensor 2 voltage within the specified range?

0.28-0.81 V

Go to Step 9

Go to Step 4

4

Is DTC P1518 also set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 9

5

  1. Open the throttle blade to wide open throttle (WOT) by hand.
  2. Observe the TP sensor 1 voltage parameter on the scan tool.

Is the TP sensor 1 voltage parameter more than the specified value?

4.51 V

Go to Step 9

Go to Step 6

6

  1. Disconnect the TP sensor harness connector.
  2. Disconnect the TAC module harness connector containing the TP sensor circuits.
  3. Test the TP sensor low-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 32

Go to Step 7

7

  1. Turn OFF the ignition for 15 seconds.
  2. Connect the throttle actuator control (TAC) module harness connector.
  3. Connect the throttle body harness connector.
  4. Install the air inlet duct.
  5. Turn ON the ignition, with the engine OFF.
  6. Select the DTC Info option on the scan tool.
  7. Lightly touch and move the related engine wiring harnesses and connectors for the TP sensor while observing the DTC Info. The DTC will set if an intermittent condition is present. Refer to Connector Repairs and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 32

Go to Step 8

8

  1. Continue to observe DTC Info.
  2. Slowly depress the accelerator pedal to WOT, then slowly return the pedal to the released position 3 times.

Does the scan tool indicate this DTC failed this ignition?

--

Go to Step 27

Go to Diagnostic Aids

9

  1. Disconnect the TP sensor harness connector.
  2. Measure the voltage at the TP sensor 1 signal circuit with a DMM connected to ground.

Is the voltage within the specified range?

3.94-6.06 V

Go to Step 14

Go to Step 10

10

  1. Turn OFF the ignition.
  2. Disconnect the TAC module harness connector containing the TP sensor circuits.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the TP sensor 1 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 32

Go to Step 11

11

Test the TP sensor 1 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 32

Go to Step 12

12

Test the TP sensor 1 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 32

Go to Step 13

13

  1. Disconnect the other TAC module harness connector.
  2. Test for a short between the TP sensor 1 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 32

Go to Step 28

14

Measure the voltage from the TP sensor 1, 5-volt reference circuit to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage within the specified range?

4.54-5.21 V

Go to Step 24

Go to Step 15

15

Is the voltage more than the specified value?

5.21 V

Go to Step 16

Go to Step 18

16

  1. Turn OFF the ignition.
  2. Disconnect the TAC module harness connector containing the TP sensor circuits.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the TP sensor 1, 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 32

Go to Step 17

17

  1. Turn OFF the ignition.
  2. Disconnect the accelerator pedal position (APP) sensor harness connector.
  3. Disconnect the other TAC module harness connector.
  4. Turn ON the ignition, with the engine OFF.
  5. Test the APP sensor 1, 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 32

Go to Step 22

18

Disconnect the APP sensor.

Is the voltage less than the specified value?

4.54 V

Go to Step 19

Go to Step 30

19

  1. Disconnect the TAC module harness connector containing the TP sensor circuits.
  2. Test the TP sensor 1, 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 32

Go to Step 20

20

Test the TP sensor 1, 5-volt reference circuit for a short to ground with a DMM.

Did you find and correct the condition?

--

Go to Step 32

Go to Step 21

21

Test the APP sensor 1, 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 32

Go to Step 22

22

Test for a short between the TP sensor 1, 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 32

Go to Step 23

23

Test for a short between the APP sensor 1, 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 32

Go to Step 28

24

  1. Connect a fused jumper between the TP sensor 1 low-reference circuit and the TP sensor 1 signal circuit.
  2. Observe the TP sensor 1 voltage parameter with a scan tool.

Is the TP sensor 1 parameter near the specified value?

0 V

Go to Step 26

Go to Step 25

25

  1. Turn OFF the ignition.
  2. Disconnect the TAC module harness connector containing the TP sensor circuits.
  3. Test the TP sensor 1 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 32

Go to Step 28

26

Inspect for an intermittent and for a poor connection at the throttle body harness connector. 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 32

Go to Step 29

27

Inspect for an intermittent and for a poor connection at the APP sensor harness connector. 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 32

Go to Step 30

28

Inspect for an intermittent and for a poor connection at the TAC module harness connector. 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 32

Go to Step 31

29

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

Did you complete the replacement?

--

Go to Step 32

--

30

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

Did you complete the replacement?

--

Go to Step 32

--

31

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

Did you complete the replacement?

--

Go to Step 32

--

32

  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 33

33

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