DTC P0122: Throttle Position Sensor (main) Circuit Low Input

CIRCUIT OPERATION

A 5-volt power supply is applied on the throttle position sensor (main) power terminal (terminal No. 5) from the ECM (terminal No. 12).
A voltage that is according to the throttle opening angle is sent to the ECM (terminal No. 10) from the throttle position sensor (main) output terminal (terminal No. 4).
The ground terminal (terminal No. 3) is grounded with ECM (terminal No. 13).

TECHNICAL DESCRIPTION

The throttle position sensor (main) outputs voltage which corresponds to the throttle valve opening angle.
The ECM checks whether the voltage is within a specified range.

DESCRIPTIONS OF MONITOR METHODS

MONITOR EXECUTION

MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored in memory for the item monitored below)

Not applicable

Sensor (The sensor below is determined to be normal)

Not applicable

DTC SET CONDITIONS

Logic Flow Chart

Check Condition

Ignition switch is "ON" position.

Judgement Criterion

Throttle position sensor (main) output voltage is less than 0.2 volt for 0.3 second.

FAIL-SAFE AND BACKUP FUNCTION

Throttle opening degree is restricted.
Throttle opening degree position is in default position if throttle position sensor (sub) fails.

OBD-II DRIVE CYCLE PATTERN

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)

Throttle position sensor failed.
Shorted throttle position sensor (main) circuit, harness damage, or connector damage.
ECM failed.

DIAGNOSIS

Required Special Tools:

MB991958: Scan Tool (M.U.T.-III Sub Assembly)

MB991824: V.C.I.
MB991827: USB Cable
MB991910: Main Harness A

MB991658: Test Harness

STEP 1. Using scan tool MB991958, check data list item 13: Throttle Position Sensor (main).

caution

To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

(1)Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)Detach the intake air hose at the throttle body.
(4)Disconnect the connector of the throttle position sensor.
(5)Use test harness special tool (MB991658) to connect only terminals No. 3, No. 4, No. 5, and No. 6.
(6)Set scan tool MB991958 to the data reading mode for item 13, Throttle Position Sensor (main).

Output voltage should be between 0.3 and 0.7 volt when the throttle valve is fully closed with your finger.
Output voltage should be 4.0 volts or more when the throttle valve is fully open with your finger.

(7)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the sensor operating properly?

It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions

Go to Step 2.

STEP 2. Check harness connector B-10 at throttle position sensor and harness connector B-108 at ECM for damage.

Q. Are the harness connectors in good condition?

	Go to Step 3.

	Repair or replace them. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 7.

STEP 3. Check for harness damage between throttle position sensor connector B-10 (terminal No. 5) and ECM connector B-108 (terminal No. 12).

Q. Is the harness wire in good condition?

	Go to Step 4.

	Repair it. Then go to Step 7.

STEP 4. Check for short circuit to ground and harness damage between throttle position sensor connector B-10 (terminal No. 4) and ECM connector B-108 (terminal No. 10).

Q. Is the harness wire in good condition?

	Go to Step 5.

	Repair it. Then go to Step 7.

STEP 5. Using scan tool MB991958, check data list item 13: Throttle Position Sensor (main).

(1)Turn the ignition switch to the "ON" position.

(2)Detach the intake air hose at the throttle body.

(3)Disconnect the connector of the throttle position sensor.

(4)Use test harness special tool (MB991658) to connect only terminals No. 3, No. 4, No. 5, and No. 6.

(5)Set scan tool MB991958 to the data reading mode for item 13, Throttle Position Sensor (main).

Output voltage should be between 0.3 and 0.7 volt when the throttle valve is fully closed with your finger.
Output voltage should be 4.0 volts or more when the throttle valve is fully open with your finger.

(6)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the sensor operating properly?

	It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .

	Go to Step 6.

STEP 6. Replace the throttle body assembly.

(1)Replace the throttle body assembly.

(2)Turn the ignition switch to the "ON" position.

(3)After the DTC has been deleted, read the DTC again.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is DTC P0122 set?

	Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP 42B, Diagnosis - ID Code Registration Necessity Judgment Table <Vehicles with KOS> or GROUP 42C, Diagnosis - ID Codes Registration Judgment Table <Vehicles with WCM> . Then go to Step 7.

	The inspection is complete.

STEP 7. Using scan tool MB991958, read the diagnostic trouble code (DTC).

(1)Turn the ignition switch to the "ON" position.

(2)After the DTC has been deleted, read the DTC again.

(3)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is DTC P0122 set?

	Retry the troubleshooting.

	The inspection is complete.