GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.0L (L34 GMDAT) 🢒 DTC 021

Circuit Description

The throttle position (TP) sensor provides a voltage signal that changes in relation to the throttle plate angle. The signal voltage will vary from about 0.4-0.8 volt at idle to nearly 5 volts at wide open throttle. The TP sensor is one of the most important inputs used by the electronic control module (ECM) for fuel control and other functions such as idle, wide open throttle, deceleration enleanment, and acceleration enrichment.

Conditions for Setting the DTC
    • The engine speed is less than 3,000 RPM.
    • The manifold absolute pressure (MAP) reading is below 85 kPa (12.3 psi).
    • The TP sensor reading is greater than 240 counts.
    • DTCs 033 and 034 are not set.
    • These conditions are present for 2 seconds.

Diagnostic Aids
    • Inspect the ECM terminals and the TP sensor connector terminals for improper mating and poor terminal-to-wire connections.
    • Observe the TP sensor voltage on a scan tool with the ignition ON and the engine stopped. Press the accelerator pedal while watching for smooth changes in the voltage readings of the TP sensor.

Step

Action

Values

Yes

No

1

Was the Diagnostic System Check performed?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Connect a scan tool to the data link connector (DLC).
  2. Turn the ignition ON.
  3. Operate the throttle lever from closed to open while watching the throttle position (TP) sensor voltage on the scan tool.

Does the scan tool show the TP sensor voltage change smoothly within the value specified?

0.10-0.9 V to 3.9-4.9 V

Go to Diagnostic Aids

Go to Step 3

3
  1. Turn the ignition to LOCK.
  2. Disconnect the TP sensor connector.
  3. Turn the ignition ON.
  4. Measure the voltage between the TP sensor connector terminals 2 and 1.

Does the voltage measure within the value specified?

4.5-5.5 V

Go to Step 4

Go to Step 5

4

Jumper the TP sensor connector terminals 2 and 3.

Does the scan tool show the TP sensor voltage above the value specified?

4 V

Go to Step 10

Go to Step 8

5

Measure the voltage between the TP sensor connector terminal 2 and ground.

Does the voltage measure within the value specified?

4.5-5.5 V

Go to Step 6

Go to Step 7

6

Inspect for a short to battery voltage in the wire between the TP sensor connector terminal 1 and the engine control module (ECM) connector terminal B2.

Is the problem found?

--

Go to Step 9

Go to Step 11

7

Inspect for a short to battery voltage in the wire between the TP sensor connector terminal 2 and the ECM connector terminal D8.

Is the problem found?

--

Go to Step 9

Go to Step 11

8

Inspect for a short to voltage in the wire between the TP sensor connector terminal 3 and the ECM connector terminal D5.

Is the problem found?

--

Go to Step 9

Go to Step 11

9
  1. Turn the ignition to LOCK.
  2. Repair the wire or the connector terminal as needed.
  3. Clear and DTCs from the ECM.
  4. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

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10
  1. Turn the ignition to LOCK.
  2. Replace the TP sensor. Refer to Throttle Position Sensor Replacement .
  3. Clear any DTCs from the ECM.
  4. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

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11
  1. Turn the ignition to LOCK.
  2. Replace the ECM. Refer to Engine Control Module Replacement .
  3. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

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