DTC P0123 Throttle Position (TP)Sensor Circuit High Voltage. Pontiac Firefly (Canada) 1999

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 1999 🢒 Firefly (Canada) 🢒 Engine 🢒 Engine Controls - 1.3L 🢒 DTC P0123 Throttle Position (TP)Sensor Circuit High Voltage

Engine Controls Components
Cell 21: Engine Data Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The throttle position (TP) sensor contains a potentiometer whose resistance value changes as the throttle valve position changes. The powertrain control module (PCM) provides a 5 volt reference voltage to the TP sensor. The PCM reads the voltage across the TP sensor and converts the voltage into a throttle angle. The TP sensor resistance decreases as the throttle-valve opening increases, and increases as the throttle-valve opening decreases. The TP sensor voltage increases as the throttle-valve opening increases.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

•	The voltage input is high, and the throttle opening is more than 96 percent.

•	The above condition is present for at least 0.5 seconds.

Action Taken When the DTC Sets

•	The PCM illuminates the malfunction indicator lamp (MIL).

•	The PCM records the operating conditions at the time that the diagnostic fails. This information is stored in the Freeze Frame buffer.

•	The PCM enters the Fail-Safe Function and assumes the throttle angle is 20 degrees.

Conditions for Clearing the DTC

•	The MIL turns OFF after 3 consecutive trips during which the diagnostic runs and does not detect a fault.

•	A History DTC clears after 40 consecutive warm-up cycles without a fault.

•	Use the Clear DTC Information function of the scan tool, or disconnect the PCM battery feed in order to clear the DTC.

Diagnostic Aids

Check for any of the following conditions:

•

Check the resistance of the TP sensor. TP sensor resistance between terminals 1 and 2 should be between 2.5k-6.0k ohms. TP sensor resistance between terminals 1 and 3 should be between 100 ohms and 20k ohms. Replace the TP sensor if the measured resistance is not within the specified values. Refer to Throttle Position Sensor Replacement .

•	Inspect the ground circuit for an open if DTC P0108, P0113,P0118, and P0123 are set together.

•	Look for a faulty electrical connection to the PCM.

An intermittent malfunction may be caused by a fault in the TP sensor electrical circuit. Inspect the wiring harness and the components for any of the following conditions:

•	Backed out terminals

•	Incorrect mating of terminals

•	Broken electrical connector locks

•	Incorrectly formed terminals or damaged terminals

•	Faulty terminal-to-wire connections

•	Physical damage to the wiring harness

•	A broken wire inside the insulation

•	Corrosion of electrical connections, of splices, or of terminals

If DTC P0123 cannot be duplicated, the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.

Test Description

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

The Powertrain OBD system check prompts the technician to complete some basic checks, and to save the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool saves the information for later reference.

Observe the TP sensor parameter from the closed throttle position to the wide open throttle position. The percentage of the TP sensor movement should not be more than 96%.

This step checks the reference voltage at the TP sensor.

Step	Action	Value(s)	Yes	No
1	Did you perform the Powertrain On--Board Diagnostic (OBD) System Check?	--	Go to Step 2	Go to Powertrain On Board Diagnostic (OBD) System Check
2	Turn ON the ignition, leaving the engine OFF. Install a scan tool. Observe the TP angle parameter on the scan tool. Check the throttle-valve opening percentage while opening the throttle valve from a closed throttle to a wide open throttle. Is the TP sensor percentage at the specified value or more than the specified value?	96%	Go to Step 4	Go to Step 3
3	Turn ON the ignition, leaving the engine OFF. Clear the scan tool information. Operate the vehicle within the Freeze Frame conditions as noted. Is the TP sensor percentage at the specified value or more than the specified value?	96%	Go to Step 4	Go to Diagnostic Aids
4	Disconnect the TP sensor electrical connector. Measure the voltage from the harness side of the TP sensor signal circuit to ground with a DMM. Is the TP sensor voltage within the specified value?	4 - 5 V	Go to Step 5	Go to Step 7
5	Measure the 5 volt reference from the harness side of the TP sensor to ground with the DMM. Is the voltage near the specified value?	5.0 V	Go to Step 6	Go to Step 8
6	Probe the TP sensor ground circuit at the TP sensor harness connector with a test lamp connected to B+. Does the test lamp illuminate?	--	Go to Step 9	Go to Step 10
7	Turn OFF the ignition. Disconnect the PCM electrical connectors. Turn ON the ignition while leaving the engine OFF. Check for an open or for a short to voltage on the TP sensor signal circuit. Repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary?	--	Go to Step 13	Go to Step 12
8	Turn OFF the ignition. Disconnect the PCM electrical connectors. Turn ON the ignition while leaving the engine OFF. Check for an open or for a short to voltage on the 5 volt reference circuit. Repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary?	--	Go to Step 13	Go to Step 12
9	Check the TP sensor signal wire for a short to the 5 volt reference circuit. Repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary?	--	Go to Step 13	Go to Step 11
10	Turn OFF the ignition. Disconnect the PCM electrical connectors. Check for an open or for a poor connection in the TP sensor ground circuit. Repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary?	--	Go to Step 13	Go to Step 12
11	Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is the action complete?	--	Go to Step 13	-
12	Replace the PCM. Is the action complete?	--	Go to Step 13	-
13	Perform the Clear DTC Information function on the scan tool, and road-test the vehicle within the Freeze Frame conditions which set the DTC. Review the scan tool data, and check the data for DTCs. The repair is complete if no DTCs are displayed. Are any DTCs displayed on the scan tool?	--	Go to the applicable DTC table	System OK