Diagnostic Instructions

DTC Descriptors

DTC P0121: Throttle Position (TP) Sensor 1 Performance

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

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

DTC P0221: Throttle Position (TP) Sensor 2 Performance

DTC P0222: Throttle Position (TP) Sensor 2 Circuit Low Voltage

DTC P0223: Throttle Position (TP) Sensor 2 Circuit High Voltage

DTC P2135: Throttle Position (TP) Sensor 1-2 Correlation

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
5-Volt Reference	P0122, P0222, P2127	P0122, P0222, P2119, P2135	P0223, P2119, P2128, P2138	P0121, P0221
TP Sensor Signal 1	P0122	P0122	P0123	P0121
TP Sensor Signal 2	P0222	P0222, P2135	P0223, P0638, P2128, P2138	P0221
Low Reference	--	P0121, P0123, P0221, P0223	P0123, P0223¹	P0121, P0221
¹ Internal ECM or TP sensor damage may occur if the circuit is shorted to B+

Typical Scan Tool Data

TP Sensor

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: The engine is operating in closed loop Parameter Normal Range: TP Position Sensor 5%/4.2 Volts
5-Volt Reference	6%/0.4 Volt	0%/0 Volt	14%/5 Volts
TP Sensor Signal	6%/0 Volt	3%/0 Volt	6%/5 Volts
Low Reference	--	6%/5 Volt	--

Circuit/System Description

The throttle body assembly contains 2 throttle position (TP) sensors. The TP sensors are mounted to the throttle body assembly and are not serviceable. The TP sensors provide a signal voltage that changes relative to throttle blade angle. The engine control module (ECM) supplies the TP sensors with a common 5-volt reference circuit , a common low reference circuit, and 2 independent signal circuits. The TP sensors have opposite functionality . TP sensor 1 signal voltage increases from below 1 volt at idle to above 4 volts at wide open throttle (WOT). TP sensor 2 signal voltage decreases from above 4 volts at idle to below 1 volt at WOT.

Conditions for Running the DTC

P0121, P2135

P0122, P0123, P0222, and P0223

P0221

Conditions for Setting the DTC

P0121 and P2135

P0122

The ECM detects the TP sensor 1 signal voltage is less than 0.2 volts.

P0123

The ECM detects the TP sensor 1 signal voltage is more than 4.6 volts.

P0221

P0222

The ECM detects the TP sensor 2 signal voltage is less than 0.2 volts.

P0223

The ECM detects the TP sensor 2 signal voltage is less than 0.2 volts.

Action Taken When the DTC Sets

DTCs P0121, P0122, P0123, P0221, P0222, P0223, and P2135 are Type A DTCs.

Conditions for Clearing the DTC

DTCs P0121, P0122, P0123, P0221, P0222, P0223, and P2135 are Type A DTCs.

Diagnostic Aids

If there is a condition with the TP sensors the ECM defaults to reduced power mode for the entire ignition cycle, even if the condition is corrected.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Description and Operation

Throttle Actuator Control (TAC) System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Circuit/System Verification

1. Ignition ON, clear the DTC Info with a scan tool.
2. Start the engine, observe the scan tool TP Sensor 1 and 2 voltage parameters. TP sensor 1 and TP sensor 2 should be between 0.4-1.0 volts.
3. Observe the scan tool TP sensor 1 and 2 parameter while performing the following tests:

•	Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release the pedal. Repeat the procedure several times.

•	Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times.

•	The scan tool TP sensor 1 and 2 parameter should display Disagree.

4. Observe the scan tool DTC Information parameter. DTCs P0121, P0122, P0123, P0221, P0222, P0223, and P2135 should not set.
5. 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 List.

Circuit/System Testing

1. Ignition OFF, and the MAIN fuse removed, disconnect the throttle body harness connector.
2. Ignition OFF, test for 5 ohms of resistance between the low reference circuit and ground.

⇒	If greater than the specified range, test the low reference circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the ECM.

3. Install the MAIN fuse. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit and ground.

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.

⇒	If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Ignition ON, verify each of the scan tool TP sensor voltage parameters is less than 1.0 volt.

⇒	If greater than the specified range, test the appropriate signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

5. Connect a 3A fused jumper wire between the 5 volt reference circuit and each of the TP sensor signal circuits.
6. Observe each of the scan tool TP sensor voltage parameters. Both TP sensor voltage parameters should display 5 volts.

⇒	If less than the specified range, test the appropriate signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

7. If all circuits test normal, replace the throttle body assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.