GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1996 🢒 Blazer - 2WD 🢒 DTC 🢒 DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage

Object Number: 29964 Size: SF
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Engine Controls Components
MAP, A/C, and Fuel Tank Pressure Sensors
OBD II Symbol Description Notice

Circuit Description

The PCM supplies a 5V reference signal and a ground to the TP sensor. The TP sensor sends a voltage signal back to the PCM relative to throttle blade opening. Voltage will vary from 0.20 V at closed throttle to over 4.5 V at wide open throttle.

Conditions For Setting The DTC
    • The TP sensor reads less than 0.19V for 5 seconds.
    • The engine is running.

Action Taken When the DTC Sets
    • The Malfunction Indicator Lamp (MIL) illuminates.
    • The PCM records the operating conditions at the time the diagnostic fails. This information will be stored in The Freeze Frame and Failure Records buffers stores this information.
    • A history DTC is stored.
    • The TP angle will default to 0% when the vehicle speed is less than 2 mph. The TP angle defaults to 10% when the vehicle speed is greater than 2 mph. The scan tool shows the defaulted value.

Conditions for Clearing the MIL/DTC
    • The malfunction indicator lamp (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

Whenever this DTC cannot be duplicated, use the information included in the Freeze Frame data in order to evaluate the conditions when the DTC set.

A faulty A/C sensor could set a DTC P0122. Disconnect the A/C electrical connector. If the TP reading returns to normal, replace the A/C Refrigerant Sensor.

Test Description

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

  1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame Data and the Failure records to the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This information on the scan tool can be referred to later.

    2.

  2. The TP sensor has an auto zeroing feature. Whenever the voltage reading is between 0.20 V and 0.90 V, the PCM will automatically assume this as closed throttle position.

    3.

  3. Whenever the PCM recognizes a high voltage signal, then the PCM and wiring are OK.

    4.

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

    5.

  5. Whenever the test lamp illuminates when probing the TP signal circuit, then the TP signal circuit is shorted to ground.

    6.

  6. Before replacing the PCM, check terminals for improper mating, broken locks, or physical damage to the wiring harness. Reprogram the replacement PCM. Refer to the latest Techline information for programming procedures.

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2
  1. Turn the ignition ON leaving the engine OFF.
  2. Install a scan tool.

Is the TP sensor voltage below the specified value?

0.2 V

Go to Step 4

Go to Step 3

3
  1. Turn the ignition ON leaving the engine OFF.
  2. Review the scan tool Freeze Frame data.
  3. Make note of the scan tool Freeze Frame data.
  4. Operate the vehicle within the Freeze Frame conditions for setting this DTC as noted.

Is the TP sensor voltage below the specified value?

0.2 V

Go to Step 4

Go to Step 12

4
  1. Disconnect the TP sensor electrical connector.
  2. Jumper the 5 volt reference circuit and the TP sensor signal together at the TP sensor electrical connector.

Is the TP sensor voltage greater than the specified value?

4 V

Go to Step 10

Go to Step 5

5
  1. Connect a test lamp between B+ and the TP sensor signal circuit at the TP sensor electrical connector.

Is the TP sensor voltage greater than the specified value?

4 V

Go to Step 6

Go to Step 8

6
  1. Check the 5 volt reference circuit for an open or short to ground.
  2. Repair as necessary. Refer to Wiring Repairs in Engine Electrical.

Was a repair made?

--

Go to Step 12

Go to Step 7

7
  1. Check the 5 volt reference circuit for a poor connection at the PCM.
  2. Replace the terminals as necessary. Refer to Wiring Repairs in Engine Electrical.

Was a repair made?

--

Go to Step 12

Go to Step 11

8
  1. Check the TP signal circuit for an open, or short to ground.
  2. Repair as necessary. Refer to Wiring Repairs in Engine Electrical.

Was a repair made?

--

Go to Step 12

Go to Step 9

9
  1. Check the TP sensor signal circuit for a poor connection at the PCM.
  2. Repair as necessary. Refer to Wiring Repairs in Engine Electrical.

Was a repair made?

--

Go to Step 12

Go to Step 11

10

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

Is the action complete?

--

Go to Step 12

--

11

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 12

--

12
  1. Using the scan tool, clear the DTCs.
  2. Start the Engine.
  3. Allow the engine to idle until the engine reaches the specified temperature.
  4. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic ran and passed?

90°-95° C

Go to Step 13

Go to Step 2

13

Check if any additional DTCs are set.

Are any DTCs displayed that have not been diagnosed?

--

Go to the Applicable DTC Table

System OK