GM Service Manual Online
For 1990-2009 cars only

Refer to

Cell 20: TP and APP Sensors


Object Number: 430062  Size: FS
Engine Controls Components
Throttle Actuator Control (TAC) System Description
Cell 20: Engine Data Sensors
Cell 20: Stop Lamp Switch
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
for complete circuit details.

Circuit Description

The Throttle Position (TP) sensor is mounted on the throttle body assembly. The sensor is actually two individual Throttle Position sensors within one housing. Two separate signal, ground and 5 volt reference circuits are used in order to connect the TP sensor assembly and the Throttle Actuator Control (TAC) Module. The two sensors have opposite functionality. The TP sensor 1 signal voltage increases as the throttle opens, from below 1.0 volt at 0% throttle to above 3.5 volts at 100% throttle. The TP sensor 2 signal voltage decreases from around 3.8 volts at 0% throttle to below 1.0 volt at 100% throttle. Also observe that the signal circuit for TP Sensor 1 is pulled up to 5 volts and that the signal circuit for TP Sensor 2 is referenced to ground within the TAC Module.

Conditions for Running the DTC

    • DTCs P0606, P1517, P1518 are not set.
    • The ignition switch is in the crank or run position.
    • The ignition voltage greater than 5.23 volts.

Conditions for Setting the DTC

    • TP sensor 1 voltage is less than 0.13 volts or greater than 4.87 volts.
    • All of the above conditions met for less than 1 second.

Action Taken When the DTC Sets

    • The PCM stores the DTC information into memory when the diagnostic runs and fails.
    • The PCM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or Failure Records.
    • The TAC system operates in reduced engine power mode. If certain TAC system DTCs are set at the same time, the TAC system may command the engine to shut down.

Conditions for Clearing the MIL/DTC

    • The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Use a scan tool in order to clear the MIL and the DTC.

Diagnostic Aids

Important: 

   • Remove any debris from the PCM\TAC module connector surfaces before servicing the PCM\TAC module. Inspect the PCM\TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM\TAC modules.
   • For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616 . Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Wiring Systems.

    • The following may cause an intermittent:
       - Poor connections; Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
       - Corrosion
       - Mis-routed harness.
       - Rubbed through wire insulation.
       - Broken wire inside the insulation.
       - Inspect the TAC module connectors for signs of water intrusion. When this occurs, multiple DTCs should be set and no circuit or component conditions can be located.
    • The APP sensor 1 and the TP sensor 1 5.0 volt reference circuits are internally connected within the TAC module.
    •  The APP sensor 2 and the TP sensor 2 5.0 volt reference circuits are internally connected within the TAC module.
    • 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. Keep this in mind when reviewing captured DTC info.
    • For an intermittent, refer to Symptoms .

Test Description

The numbers below refer to the step numbers on the Diagnostic Table.

  1. Disconnect the Throttle Actuator connector before inserting fingers into the throttle bore. After you complete diagnosis, install the air inlet duct to the throttle body.

  2. This step is testing for a short to voltage on the signal circuit.

  3. This step is verifies that 5.0 volts is available to the TP sensor 1 5.0 volt reference circuit.

  4. This step is testing for a short to voltage on the 5.0 volt reference circuit.

  5. The APP sensor 1 and the TP sensor 1 share a common 5 volt reference circuit. This step tests the APP sensor 1 for a short to B+.

  6. When the TAC module detects a problem 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 problem may correct more than one DTC. Keep this in mind when reviewing the captured DTC information.

DTC P1120 - Throttle Position (TP) Sensor 1 Circuit

Step

Action

Value(s)

Yes

No

1

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

--

Go to Step 2

Go to (Link no longer avaliable)

2

Is DTC P1515, P1516, or P1518 also set?

--

Go to applicable DTC

Go to Step 3

3

  1. Remove the air inlet duct from the Throttle Body Assembly.
  2. Important: Disconnecting the throttle actuator motor connector causes additional DTCs to set.

  3. Disconnect the Throttle Actuator harness connector. Refer to (Link no longer avaliable) .
  4. Close the throttle blade completely by hand while observing the TP sensor 1 voltage on the scan tool.

Is the voltage within the specified range?

0.13-0.67V

Go to Step 4

Go to Step 7

4

Open the throttle blade to Wide Open Throttle (WOT) by hand while observing the TP sensor 1 voltage on the scan tool.

Is the voltage within the specified range?

4.09-4.87V

Go to Step 5

Go to Step 7

5

  1. Reconnect the Throttle Actuator harness connector.
  2. Turn OFF the ignition for 15 seconds.
  3. Turn ON the ignition leaving the engine OFF.
  4. Select the Diagnostic Trouble Code (DTC) option.
  5. Move the harness and the related connectors while monitoring the DTC Information.

Did the harness movement cause this DTC to Fail this Ignition?

--

Go to Step 22

Go to Step 6

6

  1. Continue to monitor DTC Information with the scan tool.
  2. Slowly depress the accelerator pedal to Wide Open Throttle (WOT) and then slowly return it to a closed throttle.

Did this DTC Fail this Ignition?

--

Go to Step 31

Go to Diagnostic Aids

7

  1. Disconnect the TP sensor harness connector.
  2. Measure the voltage at the TP sensor 1 signal circuit using the DMM (Link no longer avaliable) connected to battery ground.

Is the voltage within the specified range?

3.94-6.06V

Go to Step 12

Go to Step 8

8

  1. Turn OFF the ignition.
  2. Leave the TP sensor disconnected.
  3. Disconnect the TAC Module connector containing the TP sensor circuits. Refer to (Link no longer avaliable) .
  4. Turn ON the ignition leaving the engine OFF.
  5. Measure the voltage from the TP sensor 1 signal circuit in the TP sensor harness connector to the battery ground using the DMM (Link no longer avaliable) .

Is any voltage present?

--

Go to Step 26

Go to Step 9

9

Test the harness for continuity of the TP sensor 1 signal circuit using the DMM (Link no longer avaliable) .

Is the resistance within the specified range?

0-2ohms

Go to Step 10

Go to Step 27

10

Test the harness for continuity between the TP sensor 1 signal circuit and the battery ground using the DMM (Link no longer avaliable) .

Does the DMM indicate continuity?

--

Go to Step 28

Go to Step 11

11

Test the harness for continuity between the TP sensor 1 signal circuit, at the TAC harness connector, and all other circuits in both TAC module connectors using the DMM (Link no longer avaliable) .

Does the DMM indicate continuity?

--

Go to Step 30

Go to Step 33

12

Measure the voltage at the TP sensor 1 5.0 volt reference circuit to the battery ground using the DMM (Link no longer avaliable) .

Is the voltage within the specified range?

3.94-6.06V

Go to Step 20

Go to Step 13

13

  1. Turn OFF the ignition.
  2. Leave the TP sensor disconnected.
  3. Disconnect the TAC Module connector containing the TP sensor circuits. Refer to (Link no longer avaliable) .
  4. Turn ON the ignition leaving the engine OFF.
  5. Measure the voltage from the TP sensor 1 5.0 volt reference circuit in the TP sensor harness connector to the battery ground using the DMM (Link no longer avaliable) .

Is any voltage present?

--

Go to Step 23

Go to Step 14

14

  1. Turn OFF the ignition.
  2. Disconnect the APP sensor connector.
  3. Disconnect the other TAC Module connector. Refer to (Link no longer avaliable) .
  4. Turn ON the ignition leaving the engine OFF.
  5. Measure the voltage from the APP sensor 1 5.0 volt reference circuit in the APP sensor harness connector to the battery ground using the DMM (Link no longer avaliable) .

Is any voltage present?

--

Go to Step 23

Go to Step 15

15

Test the harness for continuity of the TP sensor 1 5.0 volt reference circuit using the DMM (Link no longer avaliable) .

Is the resistance within the specified range?

0-2ohms

Go to Step 16

Go to Step 24

16

Test the harness for continuity between the TP sensor 1 5.0 volt reference circuit and the battery ground using the DMM (Link no longer avaliable) .

Does the DMM indicate continuity?

--

Go to Step 25

Go to Step 17

17

Test the harness for continuity between the APP sensor 1 5 volt reference circuit and the battery ground using the DMM (Link no longer avaliable) .

Does the DMM indicate continuity?

--

Go to Step 25

Go to Step 18

18

Test the harness for continuity between the TP sensor 1 5.0 volt reference circuit, at the TAC harness connector, and all other circuits in both TAC module connectors using the DMM (Link no longer avaliable) .

Does the DMM indicate continuity?

--

Go to Step 30

Go to Step 19

19

Test the harness for continuity between the APP sensor 1 5 volt reference circuit, at the TAC harness connector, and all other circuits in both TAC module connectors using the DMM (Link no longer avaliable) .

Does the DMM indicate continuity?

--

Go to Step 30

Go to Step 33

20

  1. Jumper the TP sensor 1 ground circuit to the TP sensor 1 signal circuit.
  2. Monitor the TP sensor 1 voltage using a scan tool.

Is the voltage at the specified value?

0.0

Go to Step 31

Go to Step 21

21

  1. Turn OFF the ignition.
  2. Leave the TP sensor disconnected.
  3. Disconnect the TAC Module connector containing the TP sensor circuits. Refer to (Link no longer avaliable) .
  4. Test the harness for continuity of the TP sensor 1 ground circuit using the DMM (Link no longer avaliable) .

Does the DMM indicate continuity?

--

Go to Step 33

Go to Step 29

22

Repair the harness/connections as necessary. Refer to (Link no longer avaliable) in Wiring Systems.

Is the action complete?

--

Go to Step 35

--

23

Repair the short to voltage in the 5.0 volt reference circuit. Refer to (Link no longer avaliable) in Wiring Systems.

Is the action complete?

--

Go to Step 35

--

24

Repair the open/high resistance in the 5 volt reference circuit. Refer to (Link no longer avaliable) in Wiring Systems.

Is the action complete?

--

Go to Step 35

--

25

Repair the short to a ground in the 5.0 volt reference circuit. Refer to (Link no longer avaliable) in Wiring Systems.

Is the action complete?

--

Go to Step 35

--

26

Repair the signal circuit for a shorted to voltage. Refer to (Link no longer avaliable) in Wiring Systems.

Is the action complete?

--

Go to Step 35

--

27

Repair the open/high resistance in the signal circuit. Refer to (Link no longer avaliable) in Wiring Systems.

Is the action complete?

--

Go to Step 35

--

28

Repair the short to a ground in the signal circuit. Refer to (Link no longer avaliable) in Wiring Systems.

Is the action complete?

--

Go to Step 35

--

29

Repair the open/high resistance in the ground circuit. Refer to (Link no longer avaliable) in Wiring Systems.

Is the action complete?

--

Go to Step 35

--

30

Repair the circuits that are shorted together. Refer to (Link no longer avaliable) in Wiring Systems.

Is the action complete?

--

Go to Step 35

--

31

  1. Inspect for a poor connection/terminal tension at the TP sensor harness connector. Refer to (Link no longer avaliable) in Wiring Systems.
  2. If you find a poor connection repair the condition as necessary. Refer to (Link no longer avaliable) in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 32

32

Replace the throttle body assembly. Refer to (Link no longer avaliable) .

Is the action complete?

--

Go to Step 35

--

33

  1. Inspect for a poor connection/terminal tension at the TAC Module harness connector. Refer to (Link no longer avaliable) in Wiring Systems.
  2. If you find a poor connection repair the condition as necessary. Refer to (Link no longer avaliable) in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 34

34

Replace the TAC Module. Refer to (Link no longer avaliable) .

Is the action complete?

--

Go to Step 35

--

35

  1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
  2. Idle the engine at the normal operating temperature.
  3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic ran and passed?

--

Go to Step 36

Go to Step 2

36

Select the Capture Info option and the Review Info option using the scan tool.

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

--

Go to the applicable DTC table

System OK