Mercedes-Benz 300E 1993 - G - TESTS W/CODES 1993 ENGINE PERFORMANCE Mercedes-Benz Self-Diagnostics - Gasoline

Mercedes-Benz 300E 1993 - INTRODUCTION

If no faults were found while performing preliminary inspection, proceed with ENTERING SELF-DIAGNOSTICS. If no fault codes or only pass codes are present, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).

NOTE:

All voltage tests should be performed with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless specifically stated different in testing procedures.

Mercedes-Benz 300E 1993 - SELF-DIAGNOSTIC SYSTEM

NOTE:

When diagnosing vehicle, read faults before starting diagnostic work. During some testing procedures, components are disconnected with engine running causing simulated faults. Ensure faults are recorded before starting diagnostic work to ensure only actual faults are diagnosed.

Mercedes-Benz 300E 1993 - HFM-SFI

The HFM-SFI system is equipped with a self-diagnostic capability for trouble shooting. Vehicles are tested reading stored Diagnostic Trouble Codes (DTCs). Diagnostic information can be retrieved using Pulse Counter (124 589 19 21 00) and Pulse Counter Adapter (140 589 14 63 00).

Mercedes-Benz 300E 1993 - PRETEST CONDITIONS

Start and run engine until engine oil temperature is 176?F (80?C). Turn air conditioning off. Ensure shift lever is in Park. Check all fuses and replace as necessary. Verify battery voltage is 11-14 volts.

NOTE:

For component locations, seethe THEORY/OPERATION article in the ENGINE PERFORMANCE Section.

Mercedes-Benz 300E 1993 - RETRIEVING CODES HFM-SFI FAULT CODE IDENTIFICATION Diagnostic Trouble Code (DTC HFM-SFI)

1. Turn ignition off. Perform pretest conditions. See PRETEST CONDITIONS. Turn ignition on. Press push-button located on diagnostic connector in right rear corner of engine compartment for 2-4 seconds. See Fig. 1 .
2. HFM-SFI control unit will begin output of fault codes by flashing LED light on diagnostic connector. See Fig. 1 . If LED only flashes once, this indicates no fault codes are stored. If fault codes are stored, LED will flash indicating stored fault code.
3. Press push-button again for 2-4 seconds. If more fault codes are stored, LED on diagnostic connector will display next code. Continue pressing push-button for 2-4 seconds at a time until LED lights steadily indicating end of fault code display. Record all fault codes. See HFM-SFI FAULT CODE IDENTIFICATION table to identify fault code.

Fig. 1: Mercedes-Benz 300E 1993 - Component Locations - Locating Diagnostic Connector (HFM-SFI)

Mercedes-Benz 300E 1993 HFM-SFI FAULT CODE IDENTIFICATION

Fault Code	Malfunctioning Component/System
1	(1)
2	Oxygen Sensor
3	Lambda (Air/Fuel Mixture) Control
4	Secondary Air Injection
5	EGR System
6	Idle Speed Control (ISC)
7	Ignition System Defect
8	Engine Coolant Temperature Sensor
9	Intake Air Temperature
10	Hot-Film Mass Airflow Sensor
11	Engine Speed (TN) Signal
12	Oxygen Sensor Heating
13	(2)
14	(2)
15	Wide Open Throttle (WOT) Function
16	Closed Throttle Position (CTP) Function
17	Data Transfer
18	Camshaft Adjustment Solenoid
19	Fuel Injectors Or Self-Adaptation Of Emission System At Limit
20	Vehicle Speed Signal
21	Purge Switchover Valve
22	Camshaft Position Sensor
23	Intake Manifold Absolute Pressure (Engine Running)
24	Flexplate Segments (Crankshaft Position Sensor)
25	Knock Sensors
26	Upshift Delay Switchover Valve
27	(2)
28	Engine Coolant Temperature Change Monitor
(1) No faults in system. (2) Not assigned.

Mercedes-Benz 300E 1993 - CLEARING CODES HFM-SFI

Disconnect vehicle battery. Stored DTCs are now erased. If DTCs are retrieved again before operating vehicle, DTC No. 1 will not display until HFM-SFI control unit sees system is functioning properly. After HFM-SFI control unit sees system is functioning properly, DTC No. 1 will be displayed.

Mercedes-Benz 300E 1993 - ON/OFF RATIO IDENTIFICATION

NOTE:

On/off ratio is not used to diagnose HFM-SFI vehicles.