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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Grand Am 🢒 DTC 🢒 DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage

Object Number: 621259 Size: SF
Engine Controls Components
Engine Data Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The Powertrain Control Module (PCM) supplies a 5.0 V reference signal and a ground to the sensor. The throttle position (TP) sensor sends a voltage signal back to the PCM relative to the throttle plate opening. The voltage will vary from approximately 0.35 V at closed throttle, to more than 4.65 V at wide open throttle (WOT).

Conditions For Running The DTC

The engine is running.

Conditions for Setting the DTC

The TP sensor voltage is less than 0.1 V for 6.25 seconds.

Action Taken When the DTC Sets
    • The Malfunction Indicator Lamp (MIL) will illuminate after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.
    • The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.
    • A history DTC stores.
    • The coolant fan turns on.
    • The TP angle will default to 0 percent when the vehicle speed is less than 3 km/h (2 mph) and 10 percent when the vehicle speed is more than 3 km/h (2 mph). The scan tool will display the defaulted value.

Conditions for Clearing the MIL/DTC
    • The MIL will turn off after 3 consecutive ignition cycles in which the diagnostic runs without a fault.
    • A history DTC will clear after 40 consecutive warm up cycles without a fault.
    • Use a scan tool to clear the DTCs.

Diagnostic Aids

If a DTC P0122 cannot be duplicated, the information included in the Freeze Frame data can be useful. Use the scan tool DTC information data in order to determine the status of the DTC. If the DTC occurs intermittently, use the DTC P0105 Diagnostic table in order to help isolate the problem.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The TP sensor has an auto-zeroing feature. If the voltage reading is between 0.20 volts and 0.90 volts, the PCM will automatically assume this as a closed throttle position (0 percent).

    2.

  2. This simulates a DTC P0123. If the PCM recognizes the high voltage signal, this indicates that the PCM and the wiring are OK.

    3.

  3. This simulates a high voltage signal which will identify an open in the signal circuit.

    4.

  4. Important: The PCM uses a single internal 5.0 volt power supply to supply power to all the engine control components. If one component shorts the 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.

    If any additional DTCs are set, check the 5.0 volt reference circuits for a short to ground.

    5.

  5. If the test lamp illuminates while probing the TP signal circuit terminal in step 5, then the TP signal circuit is shorted to ground.

    6.

  6. The replacement PCM must be reprogrammed and the Crankshaft Position System Variation Learn procedure must be preformed.

DTC P0122-Throttle Position (TP) Sensor Circuit Low Voltage

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

Turn on the ignition, leaving the engine off.

Is the TP sensor voltage less than the specified value?

0.2 V

Go to Step 4

Go to Step 3

3
  1. Review and record the Freeze Frame data.
  2. Operate the vehicle within the Freeze Frame conditions and the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

--

Go to Step 4

Go to Diagnostic Aids

4
  1. Turn off the ignition.
  2. Disconnect the TP sensor connector.
  3. Connect a fused jumper between the TP sensor 5.0 volt reference circuit and the signal circuit at the connector:
  4. Turn on the ignition, leaving the engine off.

Is the TP sensor voltage more than the specified value?

4.0 V

Go to Step 10

Go to Step 5

5
  1. Remove the fuse jumper.
  2. Connect a test lamp between B+ and the TP sensor signal circuit.

Is the TP sensor voltage more than the specified value?

4.0 V

Go to Step 6

Go to Step 8

6

Important: The PCM uses a single internal 5.0 volt power supply to supply power to all the engine control components. If one component shorts the 5.0 volt reference circuit to ground or to battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.

  1. Turn off the ignition.
  2. Test for the following conditions in the 5.0 V reference circuit:
    3. • An open circuit
    • A short to ground
  3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 7

7
  1. Inspect the 5.0 V reference circuit for a poor connection at the PCM connector.
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 12

8
  1. Turn off the ignition.
  2. Test the TP sensor signal circuit for the following conditions:
    3. • An open circuit
    • A short to ground
  3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 9

9
  1. Inspect the TP sensor signal circuit for a poor connection at the PCM connector.
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 12

10
  1. Turn off the ignition.
  2. Inspect for a poor connection at the TP sensor connector.
  3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

11

Replace the TP sensor. Refer to Throttle Position Sensor Replacement .

Did you complete the repair?

--

Go to Step 13

--

12

Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the repair?

--

Go to Step 13

--

13
  1. Use a scan tool to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK