GM Service Manual Online
For 1990-2009 cars only

Object Number: 548593  Size: MF
Engine Controls Components
Engine Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The throttle position (TP) sensor is mounted on the throttle body/TAC assembly. The sensor is actually two individual throttle position sensors within one housing. Two separate signal, ground and reference circuits are used in order to connect the TP sensor assembly and the throttle actuator control (TAC) module. The TP sensor signal voltage increases as the throttle opens. The signal circuit for TP Sensor is pulled up to reference voltage.

Conditions for Running the DTC

    • DTCs P0606, P1517, P1518 are not set.
    • The ignition switch is in the crank or run position.
    • The ETC serial data is operational.

Conditions for Setting the DTC

TP sensor 1 voltage is less than 0.34 volts or more than 4.4 volts as observed on the scan tool.

Action Taken When the DTC Sets

    • The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic runs and fails.
    • If equipped with traction control, the PCM will command the EBTCM via the serial data circuit to turn OFF traction control and illuminate the TRACTION OFF lamp.
    • The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

Conditions for Clearing the MIL/DTC

    • The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed.
    • The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
    • The DTC can be cleared by using a scan tool.

Diagnostic Aids

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.

Inspect for the following:

Many situations may lead to an intermittent condition. Perform each inspection or test as directed.

Important: :  Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

    • Loose terminal connection
       -  Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair.
       -  Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair.
    • Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair.
    •  Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair.

If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.

DTC P1120, 1220 - TP Sensor Ckts

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

Important: If the code does not set this ignition, refer to Diagnostic Aids.

  1. Turn ON the ignition.
  2. With a scan tool, observe the TP sensors Disagree parameter.

Does the scan tool indicate YES?

--

Go to Step 3

Go to Step 11

3

  1. With a scan tool, observe the TP sensor voltage parameter.
  2. Depress the throttle to wide open throttle (WOT) and release.

Does the scan tool indicate voltage at or near the specified value throughout throttle travel?

1 V

Go to Step 21

Go to Step 4

4

Does scan tool indicate voltage below the specified value throughout throttle travel?

1 V

Go to Step 5

Go to Step 7

5

  1. With a scan tool, observe the TP sensor voltage parameter.
  2. Disconnect the TAC throttle body.

Does the scan tool indicate voltage at or near the specified value when the TAC is disconnected?

5 V

Go to Step 6

Go to Step 13

6

  1. Turn OFF the ignition for 15 seconds.
  2. Turn ON the ignition.
  3. Measure the voltage on the reference circuit using a DMM that is connected to a good ground.

Does the voltage measure within the specified range?

3.9-4.6V

Go to Step 23

Go to Step 17

7

  1. Disconnect the TAC / throttle body.
  2. Turn ON the ignition.
  3. With a scan tool, observe the TP sensor voltage parameter.
  4. Connect a test lamp between the signal and return circuits.

Does the scan tool indicate voltage at the specified value when the test lamp is installed?

0V

Go to Step 10

Go to Step 8

8

  1. Remove the test lamp from the return circuit.
  2. Connect the test lamp to a good ground.

Does the scan tool indicate voltage at the specified value when the test lamp is installed?

0V

Go to Step 14

Go to Step 9

9

Did the test lamp illuminate when the it was connected between the signal circuit and ground?

--

Go to Step 15

Go to Step 16

10

  1. Turn OFF the ignition for 15 seconds.
  2. Turn ON the ignition.
  3. Measure the voltage on the reference circuit using a DMM that is connected to a good ground.

Does the voltage measure within the specified range?

3.9-4.6V

Go to Step 23

Go to Step 18

11

Inspect the ELEC THROT CONT and TCS BATT fuses.

Are the fuses OK?

--

Go to Step 12

Go to Step 19

12

  1. Disconnect the TAC module.
  2. Probe the feed circuits using a test lamp with a test lamp that is connected to a good ground.

Does the test lamp illuminate when probing the feed circuits?

--

Go to DTC P1515 Control Module Throttle Actuator Position Performance or DTC P1516 Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance

Go to Step 20

13

Test the signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 26

14

Test the return circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 25

15

Test the signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 26

16

Test the signal circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 25

17

Test the reference circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 25

18

Test the reference circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 26

19

Repair the short to ground in the feed circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 27

--

20

Repair the open in the feed circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 27

--

21

Test the return circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 22

22

Test for continuity between the reference circuit in the TAC and ground. Refer to Circuit Testing in Wiring Systems.

Is continuity indicated?

--

Go to Step 24

Go to Step 26

23

Inspect for a poor connection at the TAC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 24

24

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

Did you complete the replacement?

--

Go to Step 27

--

25

Inspect for a poor connection at the TAC module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 26

26

Replace the TAC module. Refer to Accelerator Pedal Replacement .

Did you complete the replacement?

--

Go to Step 27

--

27

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

Does the DTC reset?

--

Go to Step 2

Go to Step 28

28

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

--

Go to applicable DTC

System OK