GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2001 🢒 Regal (China) 🢒 DTC 🢒 DTC P1122

Circuit Description

The throttle position (TP) sensor is used by the PCM to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with three circuits, 5 volt reference, low reference, and signal. Rotation of the TP sensor rotor from the closed throttle position to the wide open throttle (WOT) position provides the PCM with a signal voltage from below 1 volt to greater than 4 volts through the TP sensor signal circuit. If the PCM detects an intermittent excessively low signal voltage, This DTC will set.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

TP sensor intermittently indicates a throttle position signal less than 0.95 volts.

The above conditions are present for 0.5 seconds

Action Taken When the DTC Sets

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

Conditions for Clearing the MIL/DTC
    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • The history DTC clears after 40 malfunction free warm-up cycles.
    • The PCM receives a clear code command from the scan tool.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This test will determine an intermittent faulty TP sensor utilizing the DMMs MIN MAX, 100 millisecond capture mode.

DTC P1122 Throttle Position (TP) Sensor Intermittent Low Voltage

Step

Action

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

Test the 5 volt reference circuit of the TP sensor for an intermittent open, high resistance and short to ground.

  1. Turn OFF the ignition.
  2. Disconnect the TP sensor.
  3. Connect a DMM between the TP sensor 5 volt reference circuit at the TP sensor harness connector and ground.
  4. Turn ON the ignition.
  5. Lightly touch and move the related engine wiring harnesses and connectors for all 5 volt reference circuits while observing voltage. Any change in voltage indicates the area where a 5 volt reference circuit fault may be found. Refer to Circuit Testing and Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 3

3

Test the signal circuit of the TP sensor for an intermittent open, high resistance and short to ground.

  1. Reconnect the TP sensor.
  2. Install a scan tool and observe the TP voltage parameter.
  3. Lightly touch and move the related engine wiring harnesses and connectors for the TP signal circuit while observing voltage. Any change in voltage indicates the area where a TP signal circuit fault may be found. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 4

4

Inspect for poor connections at the TP sensor harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 5

5

Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 6

6

  1. Connect two jumper wires at the TP sensor, one at the signal terminal, one at the 5 volt reference terminal.
  2. With a DMM set to 40k ohms scale, connect the DMM to the jumper wires.
  3. Ensure a good, proper connection at the TP sensor and DMM test leads.
  4. Press the MIN MAX button on the DMM.
  5. Slowly depress the accelerator pedal to wide open throttle (WOT) and back to the closed throttle position several times.
  6. Press the MIN MAX button and record the MAX reading.
  7. Press the MIN MAX button again and record the MIN reading.
  8. Remove the jumper wire at the 5 volt reference terminal and connect it to the low reference terminal and repeat steps 2 through 7.

Did you record a MAX value of OL or record a MIN value of 0 ohms in either test?

Go to Step 7

Go to Intermittent Conditions

7

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

Did you complete the replacement?

Go to Step 8

--

8
  1. Use a 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.

Does the DTC run and pass?

Go to Step 9

Go to Step

9

With a scan tool, observe the stored information in Captured Info.

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

Go to Diagnostic Trouble Code (DTC) List

System OK