STEP 2. Using scan tool MB991958, read the diagnostic trouble code. 
(1) | caution | To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958. | 
Connect scan tool MB991958. Refer to "How to connect scan too (M.U.T.-III) 

."
 (2) Turn the ignition switch to the "ON" position.
(3) Check whether the ETACS-ECU related DTC is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the DTC set?
Diagnose the ETACS-ECU. Refer to ETACS, Diagnosis 
.
Go to Step 3.