Diagnostic Trouble Code (DTC LH-SFI)

Turn ignition off. Perform pretest conditions. See PRETEST CONDITIONS. Before using DTCs to diagnose vehicle, LH-SFI control unit must first be allowed to display on/off ratio through On/Off Ratio Tester (909 589 00 21 00). See ON/OFF RATIO OUTPUT (LH-SFI) under RETRIEVING CODES.
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 . Connect Red wire of pulse counter to pulse counter adapter terminal No. 3. Connect Black wire of pulse counter to pulse counter adapter terminal No. 1.

Pulse counter Yellow wire is connected to pulse counter adapter depending on which module is being tested. DTCs are different for each module on vehicle. See PULSE COUNTER CONNECTION/ADAPTER IDENTIFICATION table.

PULSE COUNTER CONNECTION/ADAPTER IDENTIFICATION

Module

Adapter Terminal

Base Module ⁽¹⁾

No. 8

Cruise Control/Idle Speed Control Module ⁽²⁾

No. 7

Diagnostic Module ⁽³⁾

No. 19

Electronic Accelerator Control Module ⁽⁴⁾

No. 7

EZL/AKR Ignition Control Unit

No. 17

LH Control Unit

No. 4

⁽¹⁾	Base module will identify voltage supply malfunctions, A/C clutch, poly-V belt slipping and module box temperature.

⁽²⁾	Vehicles without Acceleration Slip Regulation (ASR).

⁽³⁾	Diagnostic module will identify malfunctions for all modules.

⁽⁴⁾	Vehicles equipped with Acceleration Slip Regulation (ASR).

Fig 1: Connecting Pulse Counter (LH-SFI Vehicles)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

After connecting Yellow wire to proper pulse counter adapter terminal, U-BATT LED on pulse counter display will illuminate if equipment is properly connected. If U-BATT LED illuminates, go to next step. If U-BATT LED does not illuminate, check pulse counter fuse. Replace as necessary. If pulse counter fuse is okay, check wiring harness between diagnostic connector and vehicle wiring harness. Repair wiring as necessary.
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.
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 appropriate table under LH-SFI FAULT CODE IDENTIFICATION to identify fault code.