GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2002 🢒 Firebird 🢒 DTC 🢒 DTC P1220

Circuit Description

The throttle position (TP) sensor is mounted on the throttle body of the TAC assembly. The sensor is actually 2 individual throttle position sensors within 1 housing. Two separate signal circuits, a low reference circuit, and a 5-volt reference circuit 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 5-volt reference voltage.

Conditions for Running the DTC
    • DTCs P0606, P1517, or P1518 are not set.
    • The ignition switch in the crank or run position.
    • The electronic throttle control (ETC) serial data is operational.

Conditions for Setting the DTC

The TP sensor 2 voltage is less than 0.25 volts, or more than 4.49 volts.

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/Failure Records.

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

When the TAC module detects a condition within the ETC system the powertrain control module (PCM) receives a message across serial data and more than 1 ETC system-related DTC may set. This condition is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Be aware of this condition when you review the captured DTC info.

If the condition is intermittent, refer to Intermittent Conditions .

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

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

  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the Agree/Disagree parameter of the TP sensors 1 and 2.

Does the scan tool indicate Disagree?

--

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, with the engine OFF.
  3. Measure the voltage on the 5-volt reference circuit using a DMM that is connected to a good ground.

Does the voltage measure within the specified values?

3.9-4.6 V

Go to Step 23

Go to Step 17

7
  1. Disconnect the throttle body of the TAC.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the TP sensor voltage parameter.
  4. Connect a test lamp between the signal and low reference circuits.

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

0 V

Go to Step 10

Go to Step 8

8
  1. Remove the test lamp from the low reference 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?

0 V

Go to Step 14

Go to Step 9

9

Did the test lamp illuminate when 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, with the engine OFF.
  3. Measure the voltage on the 5-volt reference circuit using a DMM that is connected to a good ground.

Does the voltage measure within the specified values?

3.9-4.6 V

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 or DTC P1516

Go to Step 20

13

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

Did you find and correct the condition?

--

Go to Step  27

Go to Step 26

14

Test the low reference 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 to 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 to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 25

17

Test the 5-volt reference circuit for an open or short to ground. Refer to Circuit Testing , and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 27

Go to Step 25

18

Test the 5-volt reference circuit for a short to voltage. Refer to Circuit Testing , and to 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 low reference circuit for a short to ground. Refer to Circuit Testing , and to 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 5-volt 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 to 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 of the 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 to 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 Position Sensor Replacement .

Did you complete the replacement?

--

Go to Step 27

--

27
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions For Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 28

Go to Step 2

28

With a scan tool, observe the stored information, Capture Info.

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

--

Go to Diagnostic Trouble Code (DTC) List

System OK