For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provide an overview of each diagnostic category.

### DTC Descriptors

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 | --
Idle Motor Position Signal | P0222 | P2118 | P0222 | P0223 | --
Idle Motor Switch Signal | P0510 | -- | P0510 | -- | --
Throttle Position Sensor Signal | P0122 | P0510 | P0122 | P0123 | --
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 | -- | --

### 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 %/3.66Volts
5-Volt Reference | 0 %/0.00 Volts | 0 %/0.00 Volts | 0 %/5.00 Volts
ISC Motor Position Signal | 0 %/0.00 Volts | 0 %/0.00 Volts | 0 %/5.00 Volts
Low Reference | -- | 0 %/5.00 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 %/0.40 Volts | 6 %/0.00 Volts | 14 %/5.00 Volts
Throttle Position Sensor Signal | 6 %/0.00 Volts | 6 %/0.00 Volts | 6 %/5.00 Volts
Low Reference | -- | 6 %/5.00 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:

• | A 5-volt Reference

• | ISC Motor High

• | ISC Motor Low

• | ISC Motor Position Sensor Signal

• | Idle Switch Signal

• | Low Reference

• | TP Sensor Signal

### Conditions for Running the DTC

#### P0122 or P0123

• | The ignition is ON or the engine is operating.

• | The DTCs runs continuously when the above condition is met.

#### P0222 or P0223

• | The ignition is ON or the engine is operating.

• | Ignition 1 voltage is greater than 10 volts.

• | The DTCs runs continuously when the above condition is met.

### Conditions for Setting the DTC

#### P0122

The ECM detects that the TP sensor voltage is less than 0.14 volts for 2.5 seconds.

#### P0123

The ECM detects that the TP sensor voltage is greater than 4.9 volts for 2.5 seconds.

#### P0222

The ECM detects that the ISC motor position sensor voltage is less than 0.275 volts for 1 second.

#### P0223

The ECM detects that the ISC motor position sensor voltage is greater than 4.9 volts for 1 second.

### Action Taken When the DTC Sets

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

### Conditions for Clearing the DTC

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

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

1. Start the engine, observe the TP Sensor or the ISC Motor Position Sensor parameters with a scan tool. The parameters 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 of the throttle body assembly.
2. Ignition ON, verify that the TP sensor/ISC motor position sensor voltage parameter is less than 0.3 volt.

⇒ | If greater than 0.3 volt, test the signal circuit of the TP sensor/ISC motor position sensor for a short to voltage. If the circuit/connections test normal, replace the engine control module (ECM).

Important: The test lamp is used to load the circuit and may not illuminate.

3. Ignition ON, connect a test lamp between the 5-volt reference circuit of the TP sensor/ISC motor position sensor and a good 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.

4. Test for 4.8-5.2 volts between the 5-volt reference circuit of the TP sensor/ISC motor position sensor and a good ground.

⇒ | If less than 4.8 volts, test the 5-volt reference circuit of the TP sensor/ISC motor position sensor for a short to ground or open/high resistance. If the circuit/connections test normal, replace the ECM.

⇒ | If greater than 5.2 volts, test the 5-volt reference circuit of the TP sensor/ISC motor position sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.

5. Ignition ON, test for less than 0.2 volt between the low reference circuit of the TP sensor/ISC motor position sensor and a good ground.

⇒ | If greater than 0.2 volt, test the low reference circuit of the TP sensor/ISC motor position sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.

6. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit of the TP sensor/ISC motor position sensor and a good ground.

⇒ | If greater than 5 ohms, test the low reference circuit of the TP sensor/ISC motor position sensor for an open/high resistance. If the circuit/connections test normal, replace the ECM.

7. Ignition ON, install a 3-amp fused jumper wire between the appropriate signal circuit and the 5-volt reference circuit of the TP sensor/ISC motor position sensor to verify that the TP sensor/ISC motor position sensor voltage parameter is greater than 4.8 volts.

⇒ | If less than 4.8 volts, test the appropriate signal circuit of the TP sensor/ISC motor position sensor for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the engine control module (ECM).

8. If all circuits/connections test normal, test or replace the throttle body assembly.

### Component Testing

#### TP Sensor

1. Ignition OFF, disconnect the harness connector of the throttle body assembly.
2. Measure for 1160-1175 ohms between the 5-volt reference and the low reference terminals of the TP sensor.

⇒ | If the resistance is not within the specified range, replace the throttle body assembly.

3. Measure the resistance between the signal terminal and the low reference terminal of the throttle body assembly. Sweep the TP sensor through the entire range. The resistance should vary between 1530 and 630 ohms without any spikes or dropouts.

⇒ | If the resistance is 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 TP sensor, and measure the voltage between the signal and the low reference terminals. Sweep the TP sensor through the entire range. The voltage should vary between 4.3-0.6 volts without any spikes or dropouts.

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

#### ISC Motor Position Sensor

1. Ignition OFF, disconnect the harness connector of the throttle body assembly.
2. Measure for 1160-1175 ohms between the 5-volt reference and the low reference terminals of the TP sensor.

⇒ | If the resistance is not within the specified range, replace the throttle body assembly.

3. Measure the resistance between the signal terminal and the low reference terminal of the ISC motor position sensor. Sweep the ISC motor position sensor through the entire range by pushing counter-clockwise on the ISC motor shaft. The resistance should vary between 1330-1440 ohms without any spikes or dropouts.

⇒ | If the resistance is 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, and measure the voltage between the signal and the low reference terminals. Sweep the ISC motor position sensor through the entire range by pushing counter-clockwise on the ISC motor shaft. The voltage should vary between 3.5-4.2 volts without any spikes or dropouts.

⇒ | If the voltage is 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.

• | Throttle Body Assembly Replacement

• | Control Module References for engine control module replacement, setup, and programming