DTC P0121, P0122, P0123, P0222, or P0223 w/o Throttle Actuator Control

Diagnostic Instructions

DTC Descriptors

DTC P0121: Throttle Position (TP) Sensor Performance

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

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

DTC P0222:  Idle Speed Control (ISC) Motor Position Sensor Circuit Low Voltage

DTC P0223:  Idle Speed Control (ISC) Motor Position Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit	Short to Ground	High Resistance	Open	Short to Voltage	Signal Performance
5-Volt Reference	P0122, P0222	P0510, P2119	P0122, P0222	P0123, P0223	P0121
Idle Motor Position Signal	P0222	P2118	P0222	P0223	--
Idle Motor Switch Signal	P0510	--	P0510	--	--
Throttle Position Sensor Signal	P0122	P0510	P0122	P0123	P0121
Idle Motor High Control	P2101, P2118	P2101, P2118	P2101, P2118	P2101, P2118	--
Idle Motor Low Control	P2101, P2118	P2101, P2118	P2101, P2118	--	--
Low Reference	--	--	P0123, P0223	--	P0121

Typical Scan Tool Data

ISC Motor Position Sensor

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: Engine operating in Closed Loop. Parameter Normal Range: ISC Motor Position Sensor 5%/3.66 Volts
5-Volt Reference	0%/0 Volts	0%/0 Volts	0%/5 Volts
ISC Motor Position Signal	0%/0 Volts	0%/0 Volts	0%/5 Volts
Low Reference	--	0%/5 Volts	--

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 Volts	6%/0 Volts	14%/5 Volts
Throttle Position Sensor Signal	6%/0 Volts	6%/0 Volts	6%/5 Volts
Low Reference	--	6%/5 Volts	--

Circuit/System Description

The throttle body assembly uses an idle speed control (ISC) system that contains a motor, throttle position (TP) sensor, motor position sensor, and an idle switch. The ISC system is used to control engine speed at idle. The engine control module (ECM) uses a high and low control circuit to control the ISC motor. A 5-volt reference and low reference supplied by the ECM is shared by both the TP and ISC motor position sensors. The TP and ISC motor position sensors each have a signal circuit to feedback voltage to the ECM. The ECM commands the ISC motor by pulse width modulating the voltage on the high and low control circuits to adjust the throttle angle for idle speed control. The motor position sensor is used by the ECM to monitor the position of the ISC motor for idle operation. The TP sensor is used by the ECM to monitor the position of the throttle blade. An idle switch is used by the ECM to monitor when the throttle blade is at it rest position to allow the ISC motor to control idle operation. With the throttle blade at the rest position, the idle switch will be closed. When the throttle blade is opened, the idle switch will be open.

The ISC system consist of the following circuits:

Conditions for Running the DTC

P0121

P0122, P0123, P0222, or P0223

Conditions for Setting the DTC

P0121

P0122

The ECM detects that the TP sensor voltage is less than 0.3 volt for more than 2 seconds.

P0123

The ECM detects that the TP sensor voltage is more than 4.8 volts for more than 2 seconds.

P0222

The ECM detects that the ISC position sensor voltage is less than 0.3 volt for more than 1 second.

P0223

The ECM detects that the ISC position sensor voltage is more than 4.8 volts for more than 1 second.

Action Taken When the DTC Sets

DTCs P0121, P0122, P0123, P0222, and P0223 are Type B DTCs.

Conditions for Clearing the DTC

DTCs P0121, P0122, P0123, P0222, and P0223 are Type B 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. Engine idling. observe the scan tool TP Sensor or the ISC Motor Position Sensor parameters. The readings should be between 0.4-4.5 volts.
2. 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 at the throttle body assembly.
2. Ignition OFF for at least 20 seconds, test for less than 5 ohms of resistance between the low reference circuit and ground.

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

3. Ignition ON, test for less than 0.2 volt between the low reference circuit and ground.

⇒	If greater than the specified range, test the low reference circuit for a short to voltage. If the circuit tests 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.

4. Test for 4.8-5.2 volts between the 5-volt reference circuit and ground.

⇒	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.

5. Verify the scan tool TP sensor/ISC motor position sensor voltage parameter is less than 0.3 volt.

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

6. Install a 3-A fused jumper wire between the appropriate signal circuit and the 5-volt reference circuit. Verify the scan tool TP sensor/ISC motor position sensor voltage parameter is greater than 4.8 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, test or replace the throttle body assembly.

Component Testing

TP Sensor

1. Ignition OFF, disconnect the harness connector at the throttle body assembly.
2. Test for 1,160-1,175 ohms of resistance between the 5-volt reference and the low reference terminals.

⇒	If not within the specified range or is erratic, replace the throttle body assembly.

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

⇒	If not within the specified range or is erratic, replace the throttle body assembly.

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

⇒	If not within the specified range or is erratic, replace the throttle body assembly.

ISC Motor Position Sensor

1. Ignition OFF, disconnect the harness connector at the throttle body assembly.
2. Test for 1,160-1,175 ohms of resistance between the 5-volt reference and the low reference terminals.

⇒	If not within the specified range or is erratic, replace the throttle body assembly.

3. Sweep the sensor through the entire range by pushing counterclockwise on the ISC motor shaft while monitoring the resistance between the signal terminal and the low reference terminal. The resistance should vary between 1,330-1,440 ohms without any spikes or dropouts.

⇒	If not within the specified range or is erratic, replace the throttle body assembly.

4. Apply 5 volts and ground to the applicable terminals of the throttle body assembly. Sweep the sensor through the entire range by pushing counterclockwise on the ISC motor shaft while monitoring the voltage between the signal terminal and the low reference terminal. The voltage should vary between 3.5-4.2 volts without any spikes or dropouts.

⇒	If not within the specified range or is erratic, replace the throttle body assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.