Code No. P0122: Throttle Position Sensor Circuit Low Input
OPERATION
- A power voltage of 5 V is applied to the throttle body assembly connector terminal from the engine-ECU connector terminal TPS5.
- The power voltage is earthed to the engine-ECU connector terminal TPSE from the throttle body assembly connector terminal.
- The sensor signal is inputted to the engine-ECU connector terminal TPSM from the throttle body assembly output terminal.
FUNCTION
- The throttle position sensor converts the throttle valve position into voltage and inputs it into the engine-ECU.
- The engine-ECU control the throttle valve position.
TROUBLE JUDGEMENT
Check Conditions
- Battery positive voltage is 8 - 16 V
- 2 seconds later after the ignition switch has been in "ON" position or the engine has started up
Judgement Criterion
- The throttle position sensor output voltage is 0.15 V or less.
FAIL-SAFE AND BACKUP FUNCTION
- The throttle valve is opened. (electrical discontinuity)
- The DPF regeneration is prohibited.
- The EGR control is stopped (fully closed).
PROBABLE CAUSES
- Failed throttle position sensor
- Open/short circuit or harness damage in throttle position sensor circuit or loose connector contact
- Failed engine-ECU
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STEP 1. M.U.T.-III data list
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- Refer to Data List Reference Table
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- Item 45: Throttle position sensor
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Q.
Is the check result normal?
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 Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).
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 Go to Step 2.
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STEP 2. Voltage measurement at throttle body assembly connector (TPS5 line).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(3)Check the voltage between the throttle body assembly connector (TPS5 line) and body earth.
OK: 4.9 - 5.1 V
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Q.
Is the check result normal?
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Go to Step 5.
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Go to Step 3.
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STEP 3. Check of open circuit and short to earth in TPS5 line between engine-ECU connector and throttle body assembly connector.
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Q.
Is the check result normal?
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Go to Step 4.
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Repair the connector(s) or wiring harness.
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STEP 4. M.U.T.-III data list
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- Refer to Data List Reference Table .
- Item 45: Throttle position sensor
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).
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Replace the engine-ECU.
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STEP 5. Resistance measurement at throttle body assembly connector (TPSE line).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Measure the resistance between the throttle body assembly connector (TPSE line) and body earth.
OK: Continuity (2 Ω or less)
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Q.
Is the check result normal?
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Go to Step 7.
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Go to Step 6.
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STEP 6. Check of open circuit and damage in TPSE line between engine-ECU connector and throttle body assembly connector.
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Q.
Is the check result normal?
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Go to Step 4.
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Repair the connector(s) or wiring harness.
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STEP 7. Voltage measurement at throttle body assembly connector (TPSM line).
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(1)Use special tool test harness (MB991658) to connect connector, and measure at pick-up harness.
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(3)Check the voltage between the throttle body assembly connector (TPSM line) and body earth.
OK: 3.7 V or higher
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Q.
Is the check result normal?
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Go to Step 10.
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Go to Step 8.
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STEP 8. Check of short to earth in TPSM line between engine-ECU connector and throttle body assembly connector.
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Q.
Is the check result normal?
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Go to Step 9.
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Repair the connector(s) or wiring harness.
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STEP 9. Check of damage in TPS5 line between engine-ECU connector and throttle body assembly connector.
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Q.
Is the check result normal?
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Replace the throttle body assembly.
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Repair the connector(s) or wiring harness.
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STEP 10. Check of open circuit and damage in TPSM line between engine-ECU connector and throttle body assembly connector.
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Q.
Is the check result normal?
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Go to Step 4.
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Repair the connector(s) or wiring harness.
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