DTC P0123 Throttle Position (TP)Sensor Circuit High Voltage. GMC Truck Sonoma Pickup

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1998 🢒 Sonoma Pickup - 4WD 🢒 DTC 🢒 DTC P0123 Throttle Position (TP)Sensor Circuit High Voltage

Engine Controls Components
MAP, IAT, TPS, And ECT 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 volt reference signal and a ground to the sensor. The TP sensor sends a voltage signal back to the PCM relative to the throttle plate opening. The voltage will vary from approximately 0.35 volt at closed throttle, to over 4.65 volts at wide open throttle (WOT).

Conditiions for Setting the DTC

•	Engine is running.

•	The TP sensor voltage is greater than 3.9 V for 13.75 seconds.

•	MAP is less than 60 kPa.

•	Engine speed is less than 1500 RPM.

•	DTCs P0107 or P0108 not set.

•	TP sensor voltage is greater than 4.8 V.

•	DTCs P0107 or P0108 not set.

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

•	With the ignition ON and the throttle at closed position, the voltage should read between 0.20 V and 0.90 V and increase steadily to over 4.5 V at wide open throttle.

•	Check the connectors for proper mating. Replace as necessary. Repair as necessary.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored in the scan tool for later reference.

With the throttle closed, the TP sensor voltage should read less than 0.90V. If the TP sensor voltage does not read less than 0.90V check for a binding or sticking throttle cable.

With the TP sensor disconnected, the TP sensor voltage should be less than 0.2V if the PCM and wiring are OK.

Probing the ground circuit with a test light checks the circuit for high resistance which will cause a DTC P0123 to set.

A shorted 5.0 volt reference circuit will also set additional DTCs.

Replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline information for PCM reprogramming and also refer to the Crankshaft Position System Variation Learn for the Crankshaft Position System Variation Procedure.

DTC P0123-Throttle Position (TP) Sensor Circuit-High Voltage

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	Turn the ignition switch ON, with the engine OFF, throttle closed. Install a scan tool. Is the TP sensor voltage greater than the specified value?	1V	Go to Step 4	Go to Step 3
3	Turn the ignition switch ON, with the engine OFF. Review the Freeze Frame data and note the parameters. Operate the vehicle within the Freeze Frame conditions and Conditions For Setting The DTC as noted. Is the TP sensor voltage greater than the specified value?	3.9V	Go to Step 4	Go to Step 12
4	Disconnect the TP sensor electrical connector. Is the TP sensor voltage less than the specified value?	0.2V	Go to Step 5	Go to Step 6
5	Probe the TP sensor ground circuit at the TP sensor harness connector with a test light connected to B+. Does the test light illuminate?	--	Go to Step 7	Go to Step 9
6	Check the TP sensor signal circuit for a short to voltage and repair as necessary. Was a repair necessary?	--	Go to Step 12	Go to Step 11
7	Important: The Powertrain Control Module (PCM) uses a single 5.0 volt power supply to supply power to all the engine control components. If one component shorts its 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. Check the TP sensor 5V reference circuit for a short to B+ and repair as necessary. Was a repair necessary?	--	Go to Step 12	Go to Step 8
8	Check the TP sensor electrical connector for poor connection and replace the terminals as necessary. Was a repair necessary?	--	Go to Step 12	Go to Step 10
9	Check the TP sensor ground circuit for a open and repair as necessary. Was a repair necessary?	--	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	Check for a poor connection at the PCM. If connections are OK, replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete?	--	Go to Step 12	--
12	Using the scan tool, clear the DTCs. Start the engine and idle at normal operating temperature. Operate the vehicle within the conditions for setting the DTC as specified in the supporting text. Does the scan tool indicate that the diagnostic ran and passed?	--	Go to Step 13	Go to Step 2
13	Check if any additional DTCs are set. Are any additional DTCs displayed that have not been diagnosed?	--	Go to the Applicable DTC table	System OK