Diagnostic Instructions

DTC Descriptors

DTC P0121: Throttle Position Sensor 1 Performance

DTC P0122: Throttle Position Sensor 1 Circuit Low Voltage

DTC P0123: Throttle Position Sensor 1 Circuit High Voltage

DTC P0221: Throttle Position Sensor 2 Performance

DTC P0222: Throttle Position Sensor 2 Circuit Low Voltage

DTC P0223: Throttle Position Sensor 2 Circuit High Voltage

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
5-Volt Reference	P0122, P0222, P0698	P0121, P0122, P0221, P0222, P0697, P2119, P2101	P0123, P0223, P0699, P2101, P2119	P0121, P0221, P0697, P0698, P0699
TP Sensor Signal 1	P0122	P0121, P0122, P2101, P2119	P0123	P0121, P0221, P2119
TP Sensor Signal 2	P0222	P0221, P0223	P0223, P0638, P2128, P2138	P0221
Low Reference	--	P0121, P0123, P0221, P0223, P2119, P2100	P0123, P0223*	P0121, P0221
* 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 V
5 V Reference	124%/0.0 V	7%/0.0 V	113%/TP 1 4.98, TP 2, 4.50 V
TP Sensor Signal 1	4%/0.00 V	7%/0.00 V	7%/0.00 V
TP Sensor Signal 2	4%/0.00 V	4%/4.98 V	27%/4.98 V
Low Reference	--	0%/4.98 V	--

Circuit/System Description

The throttle body assembly contains 2 throttle position 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 V reference circuit , a common low reference circuit, and two independent signal circuits. The TP sensors have opposite functionality. TP sensor 1 signal voltage decreases from greater than 4 volts at idle to less than 1 volt at wide open throttle (WOT). TP sensor 2 signal voltage increases from less than 1 volt at idle to greater than 4 volts at WOT.

Conditions for Running the DTC

P0121

P0122, P0123, P0222, and P0223

P0221

Conditions for Setting the DTC

P0121

The TP sensor 1 disagrees greater than 9 percent from TP sensor 2, or TP sensor 1 disagrees greater than 9 percent from the predicted value for greater than 1 second or a cumulative of 10 seconds.

P0122

The ECM detects the TP sensor 1 signal voltage is less than 0.18 volt for greater than 1 second or a cumulative of 10 seconds.

P0123

The ECM detects the TP sensor 1 signal voltage is greater than 4.6 volts for greater than 1 second or a cumulative of 10 seconds.

P0221

The TP sensor 2 disagrees greater than 9 percent from TP sensor 1, or TP sensor 2 disagrees greater than 9 percent from the predicted value for greater than 1 second or a cumulative of 10 seconds.

P0222

The ECM detects the TP sensor 2 signal voltage is less than 0.16 volt for greater than 1 second or a cumulative of 10 seconds.

P0223

The ECM detects the TP sensor 2 signal voltage is greater than 4.9 volts for greater than 1 second or a cumulative of 10 seconds.

Action Taken When the DTC Sets

Conditions for Clearing the DTC

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

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, verify that DTC P0697, P0698, or P0699 is not set.

⇒	If a DTC is set, refer to DTC P0641-P0643, P0651-P0653, or P0697-P0699.

2. Clear the DTC Info with a scan tool.
3. Start the engine, observe the scan tool Throttle Position Sensor 1 and 2 voltage parameters. TP sensor 1 should be between 0.17-4.6 V and TP sensor 2 should be between 0.15-4.8 V.
4. Observe the scan tool Throttle Position sensor 1 and 2 parameters while performing the tests listed below. The parameter should display Agree.

•	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.

5. Observe the DTC Information with a scan tool. DTCs P0121, P0122, P0123, P0221, P0222, and P0223 should not set.
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

1. Ignition OFF, disconnect the harness connector at Q38 throttle body.
2. Ignition OFF, remove the fuse that supplies B+ to terminal 56 X2 of the ECM.

Note: The control module or the sensor may be damaged if the circuit is shorted to battery positive voltage.

3. Test for less than 5 Ω between the low reference circuit terminal C 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 K20 ECM.

4. Install fuse that supplies B+ to terminal 56 X2 of the ECM.
5. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal E and ground.

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

⇒	If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.

6. Ignition ON, verify that the scan tool Throttle Position Sensor 1 voltage parameter is less than 0.3 volt.

⇒	If greater than the specified value, test the signal circuit terminal D for a short to voltage. If the circuit tests normal, replace the K20 ECM.

7. Connect a 3 A fused jumper wire between the 5 volt reference circuit terminal E and the TP sensor 1 signal circuit terminal D. Verify the scan tool Throttle Position Sensor 1 voltage parameter is greater than 4.89 V.

⇒	If less than the specified value, test the signal circuit for an open/high resistance or for a short to ground. If the circuit tests normal, replace the K20 ECM.

8. Verify the scan tool Throttle Position Sensor 2 voltage parameter is greater than 4.97 V.

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

Note: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage.

9. Connect a 3 A fused jumper wire between the TP sensor 2 signal circuit terminal F and the low reference circuit terminal C. Verify the scan tool Throttle Position Sensor 2 voltage parameter is less than 0.10 V.

⇒	If greater than the specified value, test the signal circuit for an open/high resistance or for a short to voltage. If the circuit tests normal, replace the K20 ECM.

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.