Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1994 Mercedes Benz S350FACTORY OEM SERVICE PROCEDURE
Retrieving Codes
NOTE:
For EDS component locations, see THEORY/OPERATION
article.
- Turn ignition off. Perform pretest conditions. See PRETEST CONDITIONS . Connect Pulse Counter Adapter (140 589 14 63 00) to diagnostic connector located in right rear corner of engine compartment. Connect Pulse Counter (124 589 19 21 00) to pulse counter adapter. See Fig 1 .
- U-BATT LED on pulse counter display will illuminate if equipment is properly connected. If U-BATT LED illuminates, go to step 5). If U-BATT LED does not illuminate, check pulse counter fuse. Replace as necessary. If pulse counter fuse is okay, go to next step.
- Using a DVOM, measure voltage between pulse counter adapter terminal No. 1 and battery positive terminal. Voltage should be 11-14 volts. If voltage is not 11-14 volts, repair wiring as necessary or replace vehicle battery.
- Using a DVOM, measure voltage between pulse counter adapter terminals No. 1 and 4. Voltage should be 6-12 volts. If voltage is not 6-12 volts, repair wiring as necessary or replace vehicle battery.
- Start engine and idle. Press START button on pulse counter for 2-4 seconds maximum. Pressing push button longer than 2-4 seconds will erase code in memory. Read pulse output on pulse counter. If pulse counter displays "1", no faults are stored. If pulse counter displays a number greater than "1", faults are stored.NOTE: If codes are read with ignition on and engine off, pulse counter will display fault code for engine speed sensor.
- Press START button again for 2-4 seconds. If more fault codes are stored, pulse counter will display next code. Continue pressing START button for 2-4 seconds at a time until pulse counter displays first fault again. Record all fault codes. See FAULT CODE DEFINITION .
- If no fault codes are displayed on pulse counter, and driveability or customer complaints are present, perform functional test on Electronic Idle Speed (ELR), Exhaust Gas Recirculation (EGR) and Boost Pressure Control (P-2) systems. See appropriate FUNCTIONAL TEST chart under DIAGNOSTIC TESTS .
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.