Diagnostic Instructions

DTC Descriptor

DTC P0120 00: Throttle Position Sensor 1 Circuit

DTC P0121 00: Throttle Position Sensor 1 Circuit Low Voltage

DTC P0122 00: Throttle Position Sensor Circuit Low Voltage

DTC P0123 00: Throttle Position Sensor Circuit High Voltage

DTC P0220 00: Throttle Position Sensor 2 Circuit

DTC P0222 00: Throttle Position Sensor 2 Circuit Low Voltage

DTC P0223 00: Throttle Position Sensor 2 Circuit High Voltage

DTC P2135 00: Throttle Position Sensors 1-2 Not Plausible

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
5 volt reference	P06A3 00	P0122 00, P0222 00	P0223 00, P06A3 00, P2135	--
Throttle position sensor 1 signal	P0122 00	P0122 00, P2119 00, P2135 00, P2176	P0223 00, P2135	P2135
Throttle position sensor 2 signal	P0222 00	P0223 00, P2135 00	P0223 00, P2135 00	P2135 00
Low reference	--	P0123 00, P0223 00	--	--

Typical Scan Tool Data

Throttle Position Sensor 1

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: The engine is idling. Parameter Normal Range: Throttle position sensor 1 3.8 to 4.4 V
5 V reference	0 V	0 V	5 V
Throttle position sensor 1 signal	0 V	0 V	5 V
Throttle position sensor 1 low reference	--	4.98 V	--

Throttle Position Sensor 2

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: The engine is idling. Parameter Normal Range: Throttle position sensor 2 0.75 to 1.02 V
5 V reference	0.02 V	0 V	5 V
Throttle position sensor 2 signal	0 V	5 V	5 V
Throttle position sensor 2 low reference	--	5 V	--

Circuit/System Description

The throttle body assembly contains 2 throttle position sensors. The throttle position sensors are mounted to the throttle body assembly and are not serviceable. The throttle position sensors provide a signal voltage that changes relative to throttle blade angle. The engine control module (ECM) supplies the throttle position sensors with a common 5-volt reference circuit, a common low reference circuit, and 2 independent signal circuits.

The throttle position sensors have opposite functionality. Throttle position sensor 1 signal voltage decreases and throttle position sensor 2 signal voltage increases as the accelerator pedal increases to wide open throttle (WOT).

Conditions for Running the DTC

P0120 00, P0122 00, P0123 00, P0220 00, P0222 00, P0223 00

P0121 00

P2135 00

Conditions for Setting the DTC

P0120 00

Throttle position sensor 1 voltage is less than 0.27 V or more than 4.67 V for more than 0.5 s.

P0121 00

The ECM detects that the throttle position sensor 1 voltage is stuck in range for less than 1 s.

P0122 00

The ECM detects that the throttle position sensor 1 voltage is less than 0.27 V for more than 0.4 s.

P0123 00

The ECM detects that the throttle position sensor 1 voltage is more than 4.67 V for more than 0.4 s.

P0220 00

The throttle position sensor 2 voltage is less than 0.31 V or more than 4.7 V for more than 0.5 s.

P0222 00

The ECM detects that the throttle position sensor 2 voltage is less than 0.31 V for more than 0.4 s.

P0223 00

The ECM detects that the throttle position sensor 2 voltage is more than 4.7 V for more than 0.4 s.

P2135 00

The difference between the throttle position sensor 1 and throttle position sensor 2 exceeds a predetermined value for more than 2 s.

Action Taken When the DTC Sets

P0120 00, P0122 00, P0123 00, P0220 00, P0222 00, P0223 00, or P2135 00

P0121 00

Conditions for Clearing the DTC

Diagnostic Aids

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

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

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify DTC P06A3 00 is not set.

⇒	If the DTC is set, refer to DTC P0641, P0651, P0697, or P06A3

2. Ignition ON, observe the Throttle Position Sensor 2 parameter. The reading should be between 0.5 to4.8 V and change with accelerator pedal input.
3. Observe the Throttle Position Sensor 1 and Throttle Position Sensor 2 Agree/Disagree parameter while performing the following tests:

•	Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release 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 Throttle Position Sensor 1 and Throttle Position Sensor 2 Agree/Disagree parameter should display Agree.

4. Observe the DTC Information with a scan tool. DTCs P0120 00,P0121 00, P0122 00, P0123 00, P0221 00, P0222 00, and P0223 00 should not set.
5. Observe both Throttle Position Sensor 1 and Throttle Position Sensor 2 percentage parameters while quickly pressing the accelerator pedal from a closed throttle to WOT. Both Throttle Position Sensor 1 and Throttle Position Sensor 2 percentage parameters should change.
6. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame / failure records data.

Circuit/System Testing

Note: You must perform the circuit / system verification before proceeding with circuit / system testing.

1. Ignition OFF, disconnect the harness connector at the Q38 Throttle Body. Allow sufficient time for the K20 Engine Control Module (ECM) to completely power down.
2. Ignition OFF, test for less than 5 Ω between the low reference circuit terminal 6 and ground.

⇒	If greater than 5 Ω, test the low reference circuit for an open / high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

3. Ignition ON, test for 4.8 to 5.2 V between the 5 V reference circuit terminal 2 and ground.

⇒	If less than the specified range, test the 5 V reference circuit for a short to ground or an open / high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

⇒	If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

4. Test for less than 1 V between the Throttle Position Sensor 1 signal circuit terminal D and ground.

⇒	If greater than specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

5. Test for 4.8 to 5.2 V between the Throttle Position Sensor 2 signal circuit terminal F and ground.

⇒	If less than specified range, test the signal circuit for a short to ground, or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

⇒	If greater than specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

6. Install a 3 A fused jumper wire between Throttle Position Sensor 1 signal circuit terminal D and the 5-volt reference circuit terminal E. Verify the scan tool Throttle Position Sensor 1 voltage parameter is greater than 4.8 V.

⇒	If less than the specified range, test the signal circuit for a short to ground, or an open / high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

7. If all circuits test normal, replace the Q38 Throttle Body.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.