DTC P0123 Throttle Position (TP)Sensor Circuit High Voltage. Isuzu S/T Isuzu

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 1999 🢒 S/T Isuzu - 2WD 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 DTC P0123 Throttle Position (TP)Sensor Circuit High Voltage

Engine Controls Components
Cell 20: 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 Running the DTC

•	DTCs P0107 or P0108 are not set.

•	The engine is running.

•	The MAP is less than 60 kPa.

•	The engine speed is less than 1500 RPM.

•	DTCs P0107 or P0108 are not set.

•	The engine is running.

•	The MAP is more than 60 kPa.

•	The ngine speed is more than 1500 RPM.

Conditions for Setting the DTC

The TP sensor voltage is more than 3.9 volts for 13.75 seconds when the engine speed is less than 1500 RPM.

TP sensor voltage is more than 4.8 volts when the engine speed is more than 1500 RPM.

Action Taken When the DTC Sets

•	The Malfunction Indicator Lamp (MIL) illuminates after two consecutive igntion cycles with the malfunction present.

•	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 more 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

If a DTC P0123 cannot be duplicated, the information included in the Freeze Frame data can be useful. Use the scan tool DTC information data to determine the status of the DTC. If the DTC occurs intermittently, use the DTC P0105 Diagnostic table in order to help isolate the problem.

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

Test Description

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

The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.

With the throttle closed, the TP sensor voltage should read less than 0.80 volts. If the TP sensor voltage does not read less than 0.80 volts, check for a binding or a sticking throttle cable.

The PCM and the wiring are OK if the TP sensor voltage is less than 0.3 volts with the TP sensor electrical connector disconnected.

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

Important: The Powertrain Control Module (PCM) uses a single internal 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.

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

Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Isuzu Technical Communications System (ITCS) information for PCM programming and the Crankshaft Position System Variation Learn for the crankshaft position system variation learn procedure.

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

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 switch leaving the engine OFF. Verify that the throttle is closed. Install a scan tool. Is the TP sensor voltage greater than the specified value?	0.8 V	Go to Step 4	Go to Step 3
3	Review the Freeze Frame data and record the parameters. Start the engine. Operate the vehicle within the Freeze Frame conditions and Conditions For Setting the DTC as specified. Is the TP sensor voltage greater than the specified value?	3.9 V	Go to Step 4	Go to Step 12
4	Turn OFF the ignition switch. Disconnect the TP sensor electrical connector. Turn ON the ignition switch leaving the engine OFF. Is the TP sensor voltage less than the specified value?	0.3 V	Go to Step 5	Go to Step 6
5	Connect a test light to B+. Probe the TP sensor ground circuit terminal at the TP sensor harness electrical connector. Does the test light illuminate?	--	Go to Step 7	Go to Step 9
6	Turn OFF the ignition switch. Check the TP sensor signal circuit for a short to voltage. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary?	--	Go to Step 12	Go to Step 11
7	Important: The Powertrain Control Module (PCM) uses a single internal 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. Turn OFF the ignition switch. Check the TP sensor 5.0 V reference circuit for a short to B+. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary?	--	Go to Step 12	Go to Step 8
8	Check the TP sensor ground circuit electrical connector for a poor electrical connection. Replace the terminals as necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary?	--	Go to Step 12	Go to Step 10
9	Turn OFF the ignition switch. Check for an open in the TP sensor ground circuit. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary?	--	Go to Step 12	Go to Step 11
10	Replace the TP sensor. Refer to the Throttle Position Sensor Replacement . Is the action complete?	--	Go to Step 12	--
11	Check for a poor electrical connection at the PCM electrical connector. If the electrical connection is OK, replace the PCM. Refer to the Powertrain Control Module Replacement . Is the action complete?	--	Go to Step 12	--
12	Clear the DTCs with the scan tool. Start the engine. Idle the engine at the 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 to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed?	--	Go to applicable DTC table	System OK