Diagnostic Instructions

DTC Descriptors

DTC P0122: Throttle Position (TP) Sensor 1 Circuit Low Voltage

DTC P0123: Throttle Position (TP) Sensor 1 Circuit High Voltage

Diagnostic Fault Information

Circuit	Short to Ground	High Resistance	Open	Short to Voltage	Signal Performance
5-Volt Reference	P0122	--	P0122	P0123	--
Throttle Position Sensor Signal	P0122	--	P0122	P0123	--
Low Reference	--	--	P0123	--	--

Typical Scan Tool Data

TP Position Sensor

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: The engine is operating at idle. Parameter Normal Range: TP Position Sensor 0%
5-Volt Reference	0%	0%	99%
Throttle Position Sensor Signal	0%	0%	99%
Low Reference	--	99%	--

Circuit/System Description

The throttle position (TP) sensor is used by the engine control module (ECM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with the following 3 circuits:

The ECM provides the TP sensor with 5 volts on the 5-volt reference circuit, and a ground on the low reference circuit. The TP sensor provides a signal voltage feedback that changes relative to throttle plate angle.

Conditions for Running

Conditions for Setting the DTC

P0122

The ECM detects that the TP sensor voltage is less than 0.3 volts for 2.5 seconds.

P0123

The ECM detects that the TP sensor voltage is greater than 4.9 volts for 2.5 seconds.

Action Taken When the DTC Sets

DTCs P0122 and P0123 are Type A DTCs.

Conditions for Clearing the DTC

DTCs P0122 and P0123 are Type A DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Circuit/System Verification

1. Ignition ON, observe the TP Sensor parameters with a scan tool. Verify the TP sensor voltage is between 0.4-4.5 volts.
2. Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times. DTC P0122 or P0123 should not set.
3. Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times. DTC P0122 or P0123 should not set.
4. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the TP sensor.
2. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit of the TP sensor and ground.

⇒	If greater than 5 ohms, test the low reference circuit of the TP sensor for a short to voltage, or an open/high resistance. If the circuit/connections test normal, replace the ECM.

Important: The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit of the TP sensor and ground.

⇒	If less than 4.8 volts, test the 5-volt reference circuit of the TP sensor for a short to ground or open/high resistance. If the circuit/connections test normal, replace the ECM.

⇒	If greater than 5.2 volts, test the 5-volt reference circuit of the TP sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.

4. Using a scan tool, verify the TP sensor voltage parameter is less than 0.3 volt.

⇒	If greater than 0.3 volt, test the signal circuit of the TP sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.

5. Install a 3-amp fused jumper wire between the signal circuit and the 5-volt reference circuit of the TP sensor. Verify the TP sensor voltage parameter is greater than 4.8 volts.

⇒	If less than 4.8 volts, test the signal circuit of the TP sensor for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the ECM.

6. If all circuits/connections test normal, test or replace the TP sensor.

Component Testing

1. Ignition OFF, disconnect the harness connector of the TP sensor.
2. Measure for 1,160-1,175 ohms between the 5-volt reference and the low reference terminals of the applicable TP sensor.

⇒	If the resistance is not within the specified range, replace the TP sensor.

3. Measure the resistance between the signal terminal and the low reference terminal of the TP sensor. Sweep the TP sensor through the entire range. The resistance should vary between 1,530 and 630 ohms without any spikes or dropouts.

⇒	If the resistance is not within the specified range or is erratic, replace the TP sensor.

4. Apply 5 volts and ground to the applicable terminals of the TP sensor, and measure the voltage between the signal and the low reference terminals. Sweep the TP sensor through the entire range. The voltage should vary between 4.3-0.6 volts without any spikes or dropouts.

⇒	If the voltage is not within the specified range or is erratic, TP sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.