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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
  • Throttle position sensor (main) output voltage is out of specified range.
 
 
MONITOR EXECUTION
  • Continuous
 
 
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.
Judgment 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
  • None.
 
 
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).
cautionTo 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) Detach the intake air hose at the throttle body.
(3) Disconnect the connector of the electronic-controlled throttle valve.
(4) Use test harness special tool (MB991658) to connect only terminals No. 3, No. 4, No. 5, and No. 6.
(5) Turn the ignition switch to the "ON" position.
(6) Set scan tool MB991958 to the data reading mode for item 13, Throttle Position Sensor (main).
  • Output voltage should be between 300 and 700 millivolts when the throttle valve is fully closed with your finger.
  • Output voltage should be 4,000 millivolts or more when the throttle valve is fully open with your finger.
(7) Turn the ignition switch to the "LOCK" (OFF) position.
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-12 at electronic-controlled throttle valve and harness connector B-26 at ECM for damage.
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 electronic-controlled throttle valve connector B-12 (terminal No. 5) and ECM connector B-26 (terminal No. 12).
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 electronic-controlled throttle valve connector B-12 (terminal No. 4) and ECM connector B-26 (terminal No. 10).
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) Detach the intake air hose at the throttle body.
(2) Disconnect the connector of the electronic-controlled throttle valve.
(3) Use test harness special tool (MB991658) to connect only terminals No. 3, No. 4, No. 5, and No. 6.
(4) Turn the ignition switch to the "ON" position.
(5) Set scan tool MB991958 to the data reading mode for item 13, Throttle Position Sensor (main).
  • Output voltage should be between 300 and 700 millivolts when the throttle valve is fully closed with your finger.
  • Output voltage should be 4,000 millivolts or more when the throttle valve is fully open with your finger.
(6) Turn the ignition switch to the "LOCK" (OFF) position.
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.
Is DTC P0122 set?
Replace the ECM (Refer to, Removal and Installation ). 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.
Is DTC P0122 set?
Retry the troubleshooting.
The inspection is complete.