GM Service Manual Online
For 1990-2009 cars only

Object Number: 369636  Size: LF
Engine Controls Components
Ground for TAC Module
OBD II Symbol Description Notice
Handling ESD Sensitive Parts 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 1 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 greater than 4.4 volts as observed on the scan tool.
    • All of the above conditions met for less than 1 second.

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 and Fail Records data.

Conditions for Clearing the MIL/DTC

    • The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been 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 the scan tool.

Diagnostic Aids

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

    • The following may cause an intermittent:
       - Poor connections. Check for adequate terminal tension. Refer to Wiring Repairs for proper procedure.
       - Corrosion
       - Mis-routed harness.
       - Rubbed through wire insulation.
       - Broken wire inside the insulation.
       - Inspect the connectors for signs of water intrusion. When this occurs, multiple DTCs should be set and no circuit or component problems can be located.
    • For an intermittent, refer to Symptoms .
    • If a repair is completed and the DTC was cleared using a scan tool on the same ignition cycle, the default action will not clear until an ignition cycle has occurred.
    • 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.

Test Description

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

  1. If the scan tool indicates YES, the problem is within the TP sensor 1 Circuit. If the scan tool indicates NO the problem is within the throttle actuator circuits or the battery feed circuit.

  2. This step determines if the problem is with the TAC or the circuit.

  3. In this step the power has been removed from the signal circuit. The step determines if there is a short to voltage on the signal circuit.

  4. In this step the power has been removed from the signal circuit. The step determines if there is a short to voltage on the reference circuit.

  5. 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 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 Powertrain On Board Diagnostic (OBD) System Check

2

Important: If the scan tool indicates NO and P1515 or P1516 are not present continue with step 3 of this table.

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

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 TP Sensor voltage remain at or near the specified voltage throughout throttle travel?

1 V

Go to Step 4

Go to Step 5

4

Inspect the ELEC THROT CONT and the TCS BATT fuses.

Is either fuse open?

--

Go to Step 15

Go to Step 19

5

Important: If this DTC sets on key up, continue with step 6.

  1. Turn OFF the ignition for 15 seconds.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, select the Diagnostic Trouble Code (DTC) option and the observe Failed This Ign.
  4. Move the harness and the related connectors while observing the DTC Information.

Does the harness movement cause this DTC fail this ignition?

--

Go to Step 20

Go to Step 6

6

  1. Turn OFF the ignition.
  2. Disconnect the TAC.
  3. Measure the resistance between the reference and the return circuits at the TAC itself using a J 39200 Digital Multimeter.

Does the resistance measure within the specified range?

4.5-5.5K ohms

Go to Step 7

Go to Step 29

7

  1. Turn ON the ignition.
  2. Measure the voltage on the signal circuit using a DMM that is connected to a good ground.

Does the voltage measure within the specified range?

3.9-4.6 V

Go to Step 8

Go to Step 10

8

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?

3.9-4.6 V

Go to Step 9

Go to Step 12

9

Measure the resistance between the TP 1 and TP 2 sensor ground circuits using a DMM.

Does the resistance measure within the specified range?

0-5 ohms

Go to Step 28

Go to Step 14

10

  1. Turn OFF the ignition.
  2. Leave the TAC disconnected.
  3. Disconnect the TAC Module.
  4. Turn ON the ignition , with the engine OFF.
  5. Measure the voltage on the signal circuit in the TAC connector using a DMM that is connected to a good ground.

Does the DMM indicate any voltage present?

--

Go to Step 21

Go to Step 11

11

Test the signal circuit for a short to ground.

Did you find a problem?

--

Go to Step 22

Go to Step 16

12

  1. Turn OFF the ignition.
  2. Leave the TAC disconnected.
  3. Disconnect the TAC Module.
  4. Turn ON the ignition, with the engine OFF.
  5. Measure the voltage on the reference circuit in the TAC connector using a DMM that is connected to a good ground.

Does the DMM indicate any voltage present?

--

Go to Step 24

Go to Step 13

13

Test the reference circuit for a short to ground.

Did you find a problem?

--

Go to Step 25

Go to Step 17

14

  1. Turn OFF the ignition.
  2. Leave the TAC disconnected.
  3. Disconnect the TAC Module.
  4. Test the ground circuits for an open.

Did you find a problem?

--

Go to Step 18

Go to Step 26

15

Repair the short to ground in the TAC module battery feed or ignition feed circuits. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 32

--

16

Test for continuity between the signal circuit and all other circuits at the TAC Module connector using a DMM.

Does the DMM indicate continuity at any time during this test?

--

Go to Step 20

Go to Step 23

17

Test for continuity between the reference circuit and all other circuits at the TAC Module connector using a DMM.

Does the DMM indicate continuity at any time during this test?

--

Go to Step 20

Go to Step 27

18

Test for continuity between the ground circuit and all other circuits at the TAC Module connector using a DMM.

Does the DMM indicate continuity at any time during this test?

--

Go to Step 20

Go to Step 30

19

Repair the open or high resistance in the TAC module battery feed or ignition feed circuits. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 32

--

20

Repair the harness/connections as necessary. Refer to Wiring Repairs and Intermittents and Poor Connections Diagnosis .

Did you complete the repair?

--

Go to Step 32

--

21

Repair the short to voltage in the signal circuit. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 32

--

22

Repair the short to a ground in the signal circuit. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 32

--

23

Repair the open or high resistance in the signal circuit. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 32

Go to Step 30

24

Repair the short to voltage in the reference circuit. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 32

--

25

Repair the short to a ground in the reference circuit. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 32

--

26

Repair the open or high resistance in the ground circuit. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 32

Go to Step 30

27

Repair the open or high resistance in the reference circuit. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 32

Go to Step 30

28

Inspect for a poor connection at the TAC. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 32

Go to Step 29

29

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

Did you complete the replacement?

--

Go to Step 32

--

30

Inspect for a poor connection at the TAC Module. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 32

Go to Step 31

31

Replace the TAC Module. Refer to Accelerator Pedal Replacement .

Did you complete the replacement?

--

Go to Step 32

--

32

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

Does the DTC reset?

--

Go to Step 2

Go to Step 33

33

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

--

Go to the applicable DTC table

System OK