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Mercedes-Benz 300D 1993 - G - TESTS W/CODES 1993 ENGINE PERFORMANCE Mercedes-Benz Self-Diagnostics - Diesel
Mercedes-Benz 300D 1993 - INTRODUCTION
If no faults were found while performing preliminary inspection, proceed with self-diagnostics. If no fault codes or only pass codes are present after entering self-diagnostics, proceed to the TESTS W/O CODES article in this section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).
NOTE: Perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless specifically stated otherwise in testing procedures.
Mercedes-Benz 300D 1993 - SELF-DIAGNOSTIC SYSTEM
The Electronic Diesel System (EDS) is equipped with a self-diagnostic capability for trouble shooting, however, there is no light on instrument panel to warn driver of a system failure. If a system failure is evident, driver may experience a driveability problem.
The EDS can be tested using Pulse Counter (124 589 19 21 00), Contact Box (124 589 00 21 00), 25-Pin Test Cable (124 589 33 63 00), Test Cable (124 589 34 63 00), DVOM, and on 6-cylinder only, Pulse Counter Adapter (140 589 14 63 00).
Mercedes-Benz 300D 1993 - PRETEST CONDITIONS
Start and run engine until coolant 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 12 volts.
Mercedes-Benz 300D 1993 - RETRIEVING CODES
NOTE: For EDS component locations, see the THEORY/OPERATION article in the ENGINE PERFORMANCE Section.
Mercedes-Benz 300D 1993 - 5-Cylinder
- Turn ignition off. Perform pretest conditions. See PRETEST CONDITIONS . Connect Pulse Counter (124 589 19 21 00) to vehicle battery and diagnostic connector located in right rear corner of engine compartment. 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 diagnostic connector 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 diagnostic connector 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.
Fig. 1: Mercedes-Benz 300D 1993 - Component Locations - Retrieving Codes (5-Cylinder) - 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 FAULT CODE DEFINITION .
- If no fault codes are displayed on pulse counter and driveability or customer complaints are present, perform functional test on ELR, EGR, and P-2 control. See 5-CYLINDER FUNCTIONAL TEST CHARTS under FUNCTIONAL TESTS.
Mercedes-Benz 300D 1993 - 6-Cylinder
- 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. 2 .
- 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.
Fig. 2: Mercedes-Benz 300D 1993 - Component Locations - Retrieving Codes (6-Cylinder) - 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 ELR, EGR, and P-2 control. See 6-CYLINDER FUNCTIONAL TEST CHARTS under FUNCTIONAL TESTS.
Mercedes-Benz 300D 1993 - FAULT CODE DEFINITION
After identifying malfunctioning component or system, refer to appropriate 5-CYLINDER FAULT CODE DIAGNOSIS or 6-CYLINDER FAULT CODE DIAGNOSIS charts under DIAGNOSTIC TESTS .
Mercedes-Benz 300D 1993 5-CYLINDER FAULT CODE IDENTIFICATION
Fault Code Component/System Designation 1 (1) All Functions Normal None 2 Fuel Rack Position Sensor L7 3 Airflow Sensor B2/1 4 (2) EDS Control Unit N39 5 (3) EGR Vacuum Transducer Or EGR Valve System Y31/1 6 EDS Control Unit (Internal Power Supply) N39 7 Starter Ring Gear Speed Sensor L3 8 Engine Coolant Sensor B11/4 9 Intake Air Temperature Sensor B2/1a 10 Voltage Supply None 11 (4) ELR Actuator Y22 " Or EGR Vacuum Transducer Y31/1 12 Not Used None 13 EDS Control Unit Defective N39 14 Air Pressure Sensor B5/1 15 Boost Pressure Control/Pressure Control Flap Vacuum Transducer Or Boost Pressure Control Ckt Y31/5
(1) If no fault codes are displayed on pulse counter and driveability or customer complaints are present, perform functional test on ELR, EGR, and P-2 control. See 5-CYLINDER FUNCTIONAL TEST CHARTS under FUNCTIONAL TESTS.
(2) EDS control unit atmospheric pressure sensor is malfunctioning. Atmospheric pressure sensor is internal to EDS control unit.
(3) Pulse counter will only display at 900 RPM for at least 5 seconds. Fault is not stored.
(4) Pulse counter only displays fault code if a short circuit is present.
Mercedes-Benz 300D 1993 6-CYLINDER FAULT CODE IDENTIFICATION
Fault Code Component/System Designation 1 (1) All Functions Normal None 2 Fuel Rack Position Sensor L7 3 Airflow Sensor B2/1 4 (2) EDS Control Unit N39 5 (3) EGR Vacuum Transducer Or EGR Valve System Y31/1 6 EDS Control Unit (Internal Power Supply) N39 7 Engine Speed Sensor L3 8 Engine Coolant Sensor B11/4 9 Intake Air Temperature Sensor B2/1a 10 EDS Control Unit Power Supply N39 11 (4) ELR Actuator Y22 " Or Boost Pressure Cut-Out Switchover Valve Y31/6 " Or EGR Vacuum Transducer Y31/1 12 Not Used None 13 EDS Control Unit Defective N39 14 (5) EDS Pressure Sensor Defective B5/1 15 Boost Pressure Control Vacuum Transducer Or Defect In Boost Pressure Control Ckt Y31/4
(1) If no fault codes are displayed on pulse counter and driveability or customer complaints are present, perform functional test on ELR and EGR. See 6-CYLINDER FUNCTIONAL TEST CHARTS under FUNCTIONAL TESTS.
(2) EDS control unit atmospheric pressure sensor is malfunctioning. Atmospheric pressure sensor is internal to EDS control unit.
(3) Pulse counter will only display at 900 RPM for at least 5 seconds. Fault is not stored.
(4) Pulse counter only displays fault code if a short circuit is present.
(5) Pressure sensor is located in left rear corner of engine compartment, on firewall.
Mercedes-Benz 300D 1993 - CLEARING CODES
Disconnecting vehicle battery will not erase codes. Each code stored in EDS control unit must be erased individually. Start engine and idle. Press START button on pulse counter for 2-4 seconds maximum. Pulse counter will display fault code. Press START button again for 6-8 seconds. Fault code is erased when pulse counter no longer displays fault code. Repeat procedure for other stored fault codes. When pulse counter displays "1", no faults are stored. Disconnect test equipment.
Mercedes-Benz 300D 1993 - SENSOR SPECIFICATIONS
Mercedes-Benz 300D 1993 COOLANT TEMP SENSOR & INTAKE AIR TEMP SENSOR SPECIFICATIONS
?F (?C) Ohms Volts At Socket 68 (20) 2500-2750 3.47-4.24 86 (30) 1530-1870 3.12-3.82 104 (40) 1062-1298 2.75-3.36 122 (50) 750-916 2.37-2.89 140 (60) 540-660 2.00-2.44 158 (70) 396-484 1.67-2.04 176 (80) 294-360 1.35-1.65 194 (90) 219-267 1.10-1.34 212 (100) 167-204 .89-1.09
Mercedes-Benz 300D 1993 - FAULT CODE DIAGNOSIS EQUIPMENT CONNECTION
Turn ignition off. Disconnect EDS control unit connector. Install 25-pin Test Cable (124 589 33 63 00) between EDS control unit and EDS control unit connector. Connect Test Cable (124 589 34 63 00) between 25-pin test cable and Contact Box (124 589 00 21 00). See Fig. 3 . Connect DVOM as instructed in diagnostic information.
Fig. 3: Mercedes-Benz 300D 1993 - Component Locations - Connecting Equipment For Diagnosis
Mercedes-Benz 300D 1993 - UNDERSTANDING DIAGNOSTIC INFORMATION
NOTE: EDS control unit is referred to as N39 by the manufacturer. When diagnosing EDS, test connections are made at EDS control unit (N39) using Contact Box (124 589 00 21 00).
For reading and understanding fault code diagnosis, as an example, using DIAGNOSTIC TESTS, read 2 under IMPULSE READOUT column. Read step 2.0 under TEST STEP/TEST SCOPE column. Component being tested is fuel rack position sensor (L7). Under TEST CONNECTION column, using DVOM, measure resistance between contact box (N39) terminals No. 4 and 5. Under TEST CONDITION column, make measurement with ignition off and EDS control unit disconnected. Resistance is 46-54 ohms under NOMINAL VALUE column. If resistance is not within specification, follow instructions under POSSIBLE CAUSE/REMEDY column.
Using one other example, read 2 under IMPULSE READOUT column. Read step 2.1 under TEST STEP/TEST SCOPE column. Component being tested is fuel rack position sensor (L7). Under TEST CONNECTION column, using DVOM, measure resistance between fuel rack position sensor (L7) terminals No. 2 and 3. Under TEST CONDITION column, make measurement with ignition off and fuel rack position sensor connector disconnected. Resistance is 46-54 ohms under NOMINAL VALUE column. If resistance is not within specification, follow instructions under POSSIBLE CAUSE/REMEDY column.
Mercedes-Benz 300D 1993 - TERMINOLOGY
When using DIAGNOSTIC TESTS, terminology may differ between fault code identification and fault code diagnostic. The following components or systems may be identified 2 different ways:
- Air pressure sensor may be referred to as pressure sensor.
- Engine speed sensor may be referred to as starter ring gear speed sensor.
- Fuel rack position sensor may be referred to as control rod travel sensor.
EDS components and connections are identified by the manufacturer with special designations in diagnosis information. See the COMPONENT IDENTIFICATION table.
Mercedes-Benz 300D 1993 COMPONENT IDENTIFICATION
Component (1) Manufacturer's Designation A/C Compressor Cut-Out/EGR Microswitch S27/6 Air Pressure Sensor B5/1 Airflow Sensor Potentiometer B2/1 Boost Pressure Control Vacuum Transducer Y31/4 Boost Press. Control/Press. Control Flap Vacuum Transducer Y31/5 Boost Pressure Control Switchover Valve Y27/4 Boost Pressure Cut-Out Switchover Valve Y31/6 Control Rod Travel Sensor L7 Diagnostic Connector X11/4 EDS Control Unit (2) N39 EGR Miroswitch S27/3 EGR Switchover Valve Y27 EGR Vacuum Transducer Y31/1 ELR Actuator Y22 Engine Coolant Sensor B11/4 Engine Speed Sensor L3 Engine Speed Sensor Connector (3) L3x1 Intake Air Temperature Sensor B2/1a Key Shutoff Relay N17/3 Key Shutoff Switchover Valve Y9/1
(1) Not all components are used on all engines.
(2) EDS control unit is referred to as N39 by the manufacturer. When diagnosing EDS, test connections are made at EDS control unit (N39) using Contact Box (124 589 00 21 00).
(3) Located in right rear corner of engine compartment on 5-cylinder engine. Located on middle left side of cylinder head on 6-cylinder engine.
Mercedes-Benz 300D 1993 - DIAGNOSTIC TESTS 5-CYLINDER DIAGNOSTIC TEST CHARTS
Fig. 4: Mercedes-Benz 300D 1993 - Component Locations - 5-Cylinder Fault Code Diagnosis (1 Of 9)
Fig. 5: Mercedes-Benz 300D 1993 - Component Locations - 5-Cylinder Fault Code Diagnosis (2 Of 9)
Fig. 6: Mercedes-Benz 300D 1993 - Component Locations - 5-Cylinder Fault Code Diagnosis (3 Of 9)
Fig. 7: Mercedes-Benz 300D 1993 - Component Locations - 5-Cylinder Fault Code Diagnosis (4 Of 9)
Fig. 8: Mercedes-Benz 300D 1993 - Component Locations - 5-Cylinder Fault Code Diagnosis (5 Of 9)
Fig. 9: Mercedes-Benz 300D 1993 - Component Locations - 5-Cylinder Fault Code Diagnosis (6 Of 9)
Fig. 10: Mercedes-Benz 300D 1993 - Component Locations - 5-Cylinder Fault Code Diagnosis (7 Of 9)
Fig. 11: Mercedes-Benz 300D 1993 - Component Locations - 5-Cylinder Fault Code Diagnosis (8 Of 9)
Fig. 12: Mercedes-Benz 300D 1993 - Component Locations - 5-Cylinder Fault Code Diagnosis (9 Of 9)
Mercedes-Benz 300D 1993 - 6-CYLINDER DIAGNOSTIC CHARTS
Fig. 13: Mercedes-Benz 300D 1993 - Component Locations - 6-Cylinder Fault Code Diagnosis (1 Of 9)
Fig. 14: Mercedes-Benz 300D 1993 - Component Locations - 6-Cylinder Fault Code Diagnosis (2 Of 9)
Fig. 15: Mercedes-Benz 300D 1993 - Component Locations - 6-Cylinder Fault Code Diagnosis (3 Of 9)
Fig. 16: Mercedes-Benz 300D 1993 - Component Locations - 6-Cylinder Fault Code Diagnosis (4 Of 9)
Fig. 17: Mercedes-Benz 300D 1993 - Component Locations - 6-Cylinder Fault Code Diagnosis (5 Of 9)
Fig. 18: Mercedes-Benz 300D 1993 - Component Locations - 6-Cylinder Fault Code Diagnosis (6 Of 9)
Fig. 19: Mercedes-Benz 300D 1993 - Component Locations - 6-Cylinder Fault Code Diagnosis (7 Of 9)
Fig. 20: Mercedes-Benz 300D 1993 - Component Locations - 6-Cylinder Fault Code Diagnosis (8 Of 9)
Fig. 21: Mercedes-Benz 300D 1993 - Component Locations - 6-Cylinder Fault Code Diagnosis (9 Of 9)
Mercedes-Benz 300D 1993 - FUNCTIONAL TESTS 5-CYLINDER FUNCTIONAL TEST CHARTS
Fig. 22: Mercedes-Benz 300D 1993 - Component Locations - 5-Cylinder Functional Test (1 Of 2)
Fig. 23: Mercedes-Benz 300D 1993 - Component Locations - 5-Cylinder Functional Test (2 Of 2)
