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DIAGNOSIS & TESTING
Diagnostic Help
1. Connect X-431 3G Diagnostic tester (the latest software) to Data Link Connector (DLC), and make it
communicate with vehicle electronic module by the data network.
2. Confirm that malfunction is current, and carry out diagnostic test and repair procedures.
3. If DTC cannot be deleted, the malfunction is current.
4. Only use a digital multimeter to measure the voltage of electronic system.
5. Refer to any Technical Bulletin that may apply to the malfunction.
6. Visually check the related wire harness.
7. Check and clean all Engine Control Module (ECM) grounds related to the current DTC.
8. If multiple trouble codes were set, use circuit diagrams and look for any common ground circuit or power
supply circuit applied to the DTC.
Intermittent DTC Troubleshooting
If malfunction is intermittent, perform the following:
Check if connectors are loose.
Check if wire harnesses are worn, pierced, pinched or partially broken.
Monitor X-431 3G diagnostic tester (the latest software) data that is related to this circuit.
Wiggle related wire harnesses and connectors and observe if the signal is interrupted in the related circuit.
If possible, try to duplicate the conditions under which the DTC was set.
Look for the data that has changed or the DTC to reset during the wiggle test.
Look for broken, bent, protruded or corroded terminals.
Inspect sensors and mounting areas for damage, foreign matter, etc. that will cause incorrect signals.
Use data recorder and/or oscilloscope to help diagnose intermittent malfunctions.
Remove the Engine Control Module (ECM) from the malfunctioning vehicle and install it on a new car to
perform test. If DTC cannot be cleared, ECM is malfunctioning. If DTC can be cleared, reinstall ECM to the
original vehicle.
Ground Inspection
Groundings are very important to proper operation of circuits. Ground points are often exposed to moisture,
dirt and other corrosive environments. Corrosion (rust) can increase resistance which will change the way in
which a circuit works.
Electrical control circuits are very sensitive to proper grounding. A loose or corroded ground can seriously
affect control circuit. Perform the following operations when checking ground points:
1. Remove the ground bolt or nut.
2. Check all contact surfaces for tarnish, dirt and rust, etc.
3. Clean as necessary to ensure that contacting is in a good condition.
4. Reinstall the ground bolt or nut securely.
5. Check if add-on accessories interfere with the ground circuit.
6. If several wire harnesses are crimped into one ground terminal, check if they are installed correctly. Make
sure all wire harnesses are clean, securely fastened and well contacted without crimping any excessive
insulation coat.