DTC P0123 Throttle Position (TP)Sensor Circuit High Voltage. Chevrolet Blazer

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1996 🢒 Blazer - 2WD 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 DTC P0123 Throttle Position (TP)Sensor Circuit High Voltage

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 and a ground to the sensor. The TP sensor sends a voltage signal back to the PCM relative to throttle blade opening. The TP sensor signal voltage will vary from 0.2 V at closed throttle to over 4.5 V at wide open throttle. The TP sensor is one the most important sensor in the control of fuel delivery.

Conditions For Setting The DTC

•	The TP sensor voltage is greater than 3.9 V for 5 seconds.

•	The engine speed is less than 1500 RPM.

•	The MAP sensor is less than 65 kPa (0.33 V).

•	One or both of the following DTCs are not set P0107, P0108.

•	The TP sensor voltage is greater than 4.8 V.

•	One or both of the following DTCs are not set P0107, P0108.

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

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

The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame Data and the Failure records on 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.

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

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

A shorted 5 volt reference circuit may also set additional DTCs.

Before replacing the PCM, check terminals for improper mating, broken locks, or physical damage to the wiring harness. Reprogram 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	Turn the ignition ON leaving the engine OFF. Make sure the throttle is closed. Is the TP sensor greater than the specified value?	1 V	Go to Step 4	Go to Step 3
3	Turn the ignition ON leaving the engine off. Review the scan tool Freeze data. Make a note of the scan tool Freeze data. 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?	3.9 V	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?	0.2 V	Go to Step 5	Go to Step 6
5	Probe the TP sensor ground circuit at the TP sensor harness connector with a test lamp connected to B+. Does the test lamp turn on?	--	Go to Step 7	Go to Step 9
6	Check for a short to voltage in the TP sensor signal circuit and repair as necessary. Refer to Wiring Repairs in Engine Electrical. Was a repair made?	--	Go to Step 12	Go to Step 11
7	Check for a short to B+ on the 5 volt reference circuit. Repair as necessary. Refer to Wiring Repairs in Engine Electrical. Was a repair made?	--	Go to Step 12	Go to Step 8
8	Check for poor electrical connections at the TP sensor. Replace the terminals if necessary. Refer to Wiring Repairs in Engine Electrical. Was a repair made?	--	Go to Step 12	Go to Step 10
9	Check for an open TP sensor ground circuit. 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 the Powertrain Control Module Replacement/Programming . Is the action complete?	--	Go to Step 12	--
12	Using the scan tool, clear the DTCs. Start the Engine. Allow the engine to idle until the engine reaches the specified temperature. 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