DTC 651

Possible Causes

• •Faulty mechanical operation of the throttle
• •Incorrect ECM Service Part Number or calibration
• •Incorrect ECM calibration / incorrect Service Part Number on ECM
• •Incorrect ECM calibration or incorrect Service Part Number
• •Large manifold vacuum leak
• •Large manifold vacuum leaks
• •Mechanical throttle operation fault
• •Other active DTC codes present
• •Presence of other active DTC codes
• •Throttle mechanical operation fault

Suggested Actions

1. 1Check Service Part Number on the ECM and replace ECM if calibration is incorrect
2. 2Check Service Part Number on the ECM to ensure correct calibration, and replace ECM if incorrect
3. 3Check and correct mechanical operation of the throttle
4. 4Check and correct mechanical operation of the throttle (Refer to Engine & Component R&R Section 1E)
5. 5Check engine for and correct large manifold vacuum leaks (Refer to Fuel Systems Section 1B Symptom Diagnostics)
6. 6Check for and correct large manifold vacuum leaks
7. 7Clear DTC information from ECM using DST and road test engine to operating temperature to confirm normal operation
8. 8Clear DTC information from the ECM using the DST (Diagnostic Service Tool)
9. 9Correct mechanical operation of the throttle
10. 10Diagnose and repair any other DTC codes present before proceeding
11. 11Diagnose and repair any other active DTC codes prior to proceeding
12. 12Inspect engine for large manifold vacuum leaks and correct if found
13. 13Perform On-Board (OBD) System Check
14. 14Remove test equipment except DST, reconnect components/fuses, clear DTC information from ECM using DST, cycle ignition OFF for 30 seconds, run engine to full operating temperature, and verify normal operation with no stored codes
15. 15Verify Service Part Number on ECM and replace ECM if calibration is incorrect

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