Diagnostic Instructions

DTC Descriptors

DTC P0120: Throttle Position (TP) Sensor 1 Circuit

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

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

DTC P0220:  Throttle Position (TP) Sensor 2 Circuit

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	High Resistance	Open	Short to Voltage	Signal Performance
TP Sensor 1 Signal	P0122	P2135	P0122	P0123	P0068, P0121
TP Sensor 1 5V Reference	P0122	P2135	P0122	P0123	--
TP Sensor 1 Low Reference	--	P2135	P0123	--	--
TP Sensor 2 Signal	P0222	P2135	P0223	P0223	P0068, P0121
TP Sensor 2 5V Reference	P0222	P2135	P0222	P0223	--
TP Sensor 2 Low Reference	--	P2135	P0223	--	--

Typical Scan Tool Data

TP Sensor 1

Circuit	Short to Ground	Open	Short to Voltage
Parameter Normal Range: 0.27-4.67 V
TP Sensor 1 Signal	0 V	0 V	5 V
TP Sensor 1 5V Reference	0 V	0 V	5 V
TP Sensor 1 Low Reference	--	5 V	--

TP Sensor 2

Circuit	Short to Ground	Open	Short to Voltage
Parameter Normal Range: 0.31-4.7 V
TP Sensor 2 Signal	0 V	5 V	5 V
TP Sensor 2 5V Reference	0 V	0 V	5 V
TP Sensor 2 Low Reference	--	5 V	--

Circuit/System Description

The throttle actuator control (TAC) system uses 2 throttle position (TP) sensors to monitor the throttle position. The TP sensors 1 and 2 are located within the throttle body assembly. Each sensor has the following circuits:

Two processors are also used to monitor the TAC system data. Both processors are located within the engine control module (ECM). Each signal circuit provides both processors with a signal voltage proportional to throttle plate movement. Both processors monitor each other's data to verify that the indicated TP calculation is correct.

Conditions for Running the DTC

P0120, P0122, P0123, P0220, P0222, P0223

P2135

Conditions for Setting the DTC

P0120

TP sensor 1 voltage is less than 0.27V or more than 4.67V for more than 0.5 second.

P0122

The ECM detects that the TP sensor 1 voltage is less than 0.27V for more than 0.4 second.

P0123

The ECM detects that the TP sensor 1 voltage is more than 4.67V for more than 0.4 second.

P0220

The TP sensor 2 voltage is less than 0.31V or more than 4.7V for more than 0.5 second.

P0222

The ECM detects that the TP sensor 2 voltage is less than 0.31V for more than 0.4 second.

P0223

The ECM detects that the TP sensor 2 voltage is more than 4.7V for more than 0.4 second.

P2135

The difference between the TP sensor 1 and TP sensor 2 exceeds a predetermined value for more than 2 seconds.

P2138

The voltage difference between APP sensor 1 and APP sensor 2 exceeds a predetermined value for more than 2 seconds.

Action Taken When the DTC Sets

Conditions for Clearing the MIL/DTC

DTC P0120, P0122, P0123, P0220, P0222, P0223, and P2135 are Type A DTCs.

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 TP sensor 1 voltage parameter. The reading should be between 0.27-4.67V and change with accelerator pedal input.
2. Ignition ON, observe the TP sensor 2 voltage parameter. The reading should be between 0.31-4.7V and change with accelerator pedal input.
3. Clear the DTCs with the scan tool. Operate the vehicle within the Conditions for Running the DTC, or within the conditions that you observed from the Freeze Frame/Failure Records.
4. Verify that DTC P0120 or P0220 are not the only throttle position DTCs set.

⇒	If DTC P0120 or P0220 are the only DTCs set, replace the ECM.

5. Verify that DTCs P0641 or P0651 are set.

⇒	If DTC P0641 or P0651 is set, refer to DTC P0641 or P0651.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the Q38 throttle body. Allow sufficient time for the ECM to completely power down.
2. Ignition OFF, test for less than 5Ω between the low reference circuit terminal C and ground.

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

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

⇒	If less than 4.8V, test the 5V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.

⇒	If greater than 5.2V, test the 5V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.

4. Verify the scan tool TP sensor 1 voltage is less than 0.1V.

⇒	If greater than 0.1V, test the signal circuit terminal D for a short to voltage. If the circuit tests normal, replace the ECM.

5. Verify the scan tool TP sensor 2 voltage is greater than 4.8V.

⇒	If less than 4.8V, test the signal circuit terminal F for a short to ground. If the circuit tests normal, replace the K20 ECM.

6. Install a 3A fused jumper wire between the signal circuit terminal D and the 5V reference circuit terminal E of the TP sensor 1, verify the TP sensor 1 voltage is greater than 4.8V.

⇒	If less than 4.8V, test the TP sensor 1 signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.

7. Install a 3A fused jumper wire between the signal circuit terminal F and the low reference circuit terminal C of the TP sensor 2, verify that the TP sensor 2 voltage is less than 0.1V.

⇒	If greater than 0.1V, test the TP sensor 2 signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 ECM.

8. Ignition OFF, disconnect the harness connector at the K20 ECM.
9. Test for less than 5Ω on all TP sensor circuits between the following terminals:

•	The 5V reference circuit terminal E to the corresponding K20 ECM terminal

•	The signal circuit terminal F to the corresponding K20 ECM terminal

•	The signal circuit terminal D to the corresponding K20 ECM terminal

⇒	If greater than 5Ω, repair the affected circuit.

10. Test for infinite resistance between TP sensor 1 signal circuit terminal D and TP sensor 2 signal circuit terminal F.

⇒	If less than infinite resistance, repair the short between TP sensor 1 signal circuit and TP sensor 2 signal circuit.

11. If all circuits test normal, replace the Q38 throttle body.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.