DTC P0123 Throttle Position (TP)Sensor Circuit High Voltage. Pontiac Firefly (Canada) 1997

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 1997 🢒 Firefly (Canada) 🢒 DTC 🢒 DTC P0123 Throttle Position (TP)Sensor Circuit High Voltage

Schematic Reference: Engine Controls Schematics

Circuit Description

The throttle position (TP) sensor contains a potentiometer whose resistance value changes with the changes in the throttle valve position. 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 the TP sensor resistance increases as the throttle valve opening decreases. The TP sensor voltage being monitored by the PCM will increase as the throttle valve opening increases.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

•	A high voltage input (throttle opening is greater than 96%) is indicated at the PCM.

•	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 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 MIL/DTC

•	The MIL turns OFF after three consecutively passing trips without a fault present.

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

•	Use the scan tool Clear DTC Information function 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 2.5k ohms to 6.0k ohms. TP sensor resistance between terminals 1 and 3 should be 100 ohms to 20k ohms. Replace the TP sensor if the measured resistance is not within the specified values. Refer to Throttle Position Sensor Replacement .

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

•	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 components for any of the following conditions:

•	Backed out terminals.

•	Improper mating of terminals.

•	Broken electrical connector locks.

•	Improperly formed or damaged terminals.

•	Faulty terminal to wire connections.

•	Physical damage to the wiring harness.

•	A broken wire inside the insulation.

•	Corrosion of electrical connections, splices, or terminals.

If a DTC P0123 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was 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 store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

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

This step checks for reference voltage at the TP sensor.

Step	Action	Value(s)	Yes	No
1	Did you perform the Powertrain On-Board Diagnostic 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 closed throttle to wide open throttle. Is the TP sensor percentage at or greater 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 or greater 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 TP sensor signal circuit (harness side) to ground with a DMM. Is the TP sensor voltage within the specified value?	4 to 5 volts	Go to Step 5	Go to Step 7
5	Measure voltage from the TP sensor 5 volt reference circuit (harness side) to ground with the DMM. Is the voltage near the specified value?	5.0 volts	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, leaving the engine OFF. Check for an open or 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, leaving the engine OFF. Check for an open or 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 a poor connection in the TP sensor ground circuit. Repair as necessary. 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. Refer to Powertrain Control Module Replacement . Is the action complete?	--	Go to Step 13	--
13	Perform the scan tool Clear DTC Information function and road test the vehicle within the Freeze Frame conditions that set the DTC. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored. Are any DTCs displayed on the scan tool?	--	Go to the Applicable DTC Table	System OK