DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage. GMC Truck GMC K Sierra

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC K Sierra - 4WD 🢒 Engine 🢒 Engine Electrical 🢒 DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage

Engine Controls Component Views
Cell 21: G103, Idle Air Control Valve, MAF Sensor, TP Sensor, MAP Sensor
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The Throttle Position (TP) sensor is a potentiometer. The TP sensor is mounted to the left side of the throttle body. The TP sensor provides a voltage signal that changes relative to throttle blade angle. This signal voltage is one of the most important inputs used by the PCM. The TP sensor has a 5.0 volt reference, a ground and a signal circuit.

TP sensor Signal voltage should be near 0.6 volt at idle. The TP sensor voltage should increase to above 4.0 volts at wide open throttle (WOT).

When the PCM senses a signal voltage lower than the normal operating range of the sensor, this DTC sets.

Conditions for Running the DTC

The ignition switch is in the ON position or the engine is operating.

Conditions for Setting the DTC

•	The TP sensor signal voltage is less than 0.2 volts.

•	The above conditions present for 10.0 seconds.

Action Taken When the DTC Sets

•	The PCM illuminates the Malfunction Indicator Lamp on the second consecutive ignition cycle that the diagnostic runs and fails.

•

The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure records.

•	The PCM uses a default TP sensor value.

•	The transmission line pressure increases.

•	Firmer Transmission shifts.

Conditions for Clearing the MIL/DTC

•	The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

•	A last test failed, or current DTC, clears when the diagnostic runs and does not fail.

•	A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

•	Use a scan tool in order to clear the MIL and the DTC.

Diagnostic Aids

Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

•	The following may cause an intermittent:

-	Mis-routed harness

-	Rubbed through wire insulation

-	Broken wire inside the insulation

•

The PCM 5.0 volt reference circuits are internally connected within the PCM. If all the TP sensor circuits are OK, inspect the Fuel Tank Pressure Sensor for malfunctions. If DTC P1639 sets at the same time, this indicates that the 5.0 volt reference circuit is either shorted to a ground or shorted to a voltage. The 5.0 volt reference circuit is internally connected within the PCM.

•	If it is determined that the DTC occurs intermittently, performing the DTC P1122 diagnostic table may isolate the cause of the fault.

•	For an intermittent, refer to Symptoms .

Test Description

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

If DTC P1639 sets at the same time, this indicates that the 5 volt reference circuit is either shorted to a ground or shorted to a voltage. The 5 volt reference circuit is internally connected within the PCM.

This step verifies that a malfunction is present.

Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicated the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed. For an intermittent condition, refer to Symptoms .

If the scan tool displays 5 volts, this indicates the TP sensor signal circuit, 5 volt reference circuit and PCM are OK.

If the scan tool displays 5 volts, this indicates the TP sensor signal circuit and PCM are OK.

Disconnecting the PCM allows using the DMM J 39200 to check continuity of the circuits. This will aid in locating an open or shorted circuit. Refer to Testing for Continuity in Wiring Systems.

Disconnecting the PCM allows using the DMM J 39200 to check continuity of the circuits. This will aid in locating an open or shorted circuit. Refer to Testing for Continuity in Wiring Systems.

Inspect for poor connections at the TP sensor electrical connector before replacing the TP sensor. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

Step

Action

Value(s)

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Install the scan tool.
Idle the engine.
Monitor the Diagnostic Trouble Code (DTC) information using the scan tool.

Did DTC P1639 fail this ignition?

Go to DTC P1639 5 Volt Reference 2 Circuit

Go to Step 3

Turn ON the ignition leaving the engine OFF.
With the throttle closed, monitor the TP sensor display on the scan tool.

Is the TP sensor voltage below the specified value?

0.2V

Go to Step 5

Go to Step 4

Turn ON the ignition leaving the engine OFF.
Review the Freeze Frame and/or Failure Records data for this DTC and record the parameters.
Turn OFF the ignition for 15 seconds.
Start the engine.
Operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions recorded in Freeze Frame/Failure Records as possible. Special operating conditions that you need to meet before the PCM will run this diagnostic, where applicable, are listed in Conditions for Running the DTC.
Select the Diagnostic Trouble Code (DTC) option, the Specific DTC option, then enter the DTC number which was set using the scan tool.

Does the scan tool indicate that this diagnostic failed this ignition?

Go to Step 5

Go to Diagnostic Aids

Disconnect the TP sensor electrical connector.
Jumper the 5 volt reference circuit and the TP signal circuit together at the TP sensor harness connector.
Observe the TP sensor voltage display on the scan tool.

Is the TP sensor voltage above the specified value?

4.7V

Go to Step 11

Go to Step 6

Connect the test lamp J 35616-200 between B+ and the TP sensor signal circuit at the TP sensor harness connector.
Observe the TP sensor voltage display on the scan tool.

Is the TP sensor voltage above the specified value?

4.7V

Go to Step 7

Go to Step 9

Turn OFF the ignition.
Disconnect the PCM connector C1 located on the same side as the manufacturer's logo. Refer to Powertrain Control Module Replacement/Programming .
Check the 5 volt reference circuit for an open or short to ground.
If the 5 volt reference circuit is open or shorted to ground, repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 8

Check the 5 volt reference circuit for a poor connection at the PCM. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
If you find a poor connection replace the terminal as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

Turn OFF the ignition.
Disconnect the PCM connector C2 located on the opposite side of the manufacturer's logo. Refer to Powertrain Control Module Replacement/Programming .
Check the TP signal circuit for an open, short to ground, or for a short to the sensor ground circuit.
If you find the TP sensor signal circuit is open or shorted to ground, repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 10

Check the TP sensor signal circuit for a poor connection at the PCM. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
If you find a poor connection replace the terminal as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

Important:: Inspect for poor TP sensor connections before replacing the TP sensor. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

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

Is the action complete?

Go to Step 13

Important::

•	Inspect for poor PCM connections before replacing the PCM. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

•	Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM.

Is the action complete?

Go to Step 13

Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
Idle the engine at the normal operating temperature.
Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.

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

Go to Step 14

Go to Step 2

Select the Capture Info option and the Review Info using the scan tool.

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

Go to the applicable DTC table

System OK