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IGNITION COIL CHECK
Required Special Tool:
  • MB991958: Scan Tool (M.U.T-III Sub Assembly)
    • MB991824: V.C.I.
    • MB991827: M.U.T.-III USB Cable
    • MB991910: M.U.T.-III Main Harness A
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
noteIt is impossible to carry out an easy check using a circuit tester because a diode and so on are integrated into the inside circuit of this ignition coil. Accordingly, check the ignition coil in the following procedure.
1. Make sure the diagnosis codes are not set using scan tool MB991958. If set, record the code No. Carry out the troubleshooting for the set codes and solve the problems even if not related to the ignition.
2. Disconnect the injector connectors on all of the cylinders.
3. Disconnect the ignition coil connector.
4. Remove the ignition coil and install a good spark plug to the ignition coil.
5. Connect the ignition coil connector.
6. Ground the side electrode of the spark plug and crank the engine.
7. Check that spark is produced between the electrodes of the spark plug.
8. If the spark plug has weak spark or no spark, carry out the same check using a good ignition coil. If there is strong spark on this check with a good ignition coil, it becomes clear there is a problem with the ignition coil. Replace the ignition coil with a new one. If there is no spark on this check with a good ignition coil, there is probably a problem with the ignition circuit. Check the ignition circuit.
9. Using scan tool MB991958, make sure whether the diagnosis codes are set due to the check, or not. Except the codes set in Step 1, clear the codes all together if they are present. And then, carry out the troubleshooting about the codes recorded.
10.
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
Disconnect scan tool MB991958 to the data link connector.