AUTOMOTIVE ELECTRICIANS PORTAL
WIRING-DIAGRAMS

Mercedes-Benz 190E 1993 – G TESTS W CODES 1993 ENGINE PERFORMANCE Mercedes Benz Self Diagnostics Gasoline

  1. Home
  2. >Mercedes Benz
  3. >Mercedes-Benz 1993
  4. >Mercedes-Benz 190E 1993
  5. >Mercedes-Benz 190E 1993 - DTC - Fuses - Component Locations

Download PDF file

Mercedes-Benz 190E 1993 - G - TESTS W/CODES 1993 ENGINE PERFORMANCE Mercedes-Benz Self-Diagnostics - Gasoline


Mercedes-Benz 190E 1993 - INTRODUCTION

NOTE: Limited diagnostic information is available for 190E 2.6L.

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 190E 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 190E 1993 - CIS-E


The CIS-E system is equipped with a self-diagnostic capability for trouble shooting, however, there are 2 methods of retrieving diagnostic information. All vehicles can be tested reading an on/off ratio output as a percentage to identify malfunctioning components or systems. California vehicles can be tested reading stored Diagnostic Trouble Codes (DTC's). Only vehicles built for California have the capability to identify and store a DTC. Federal vehicles can only be diagnosed reading an on/off ratio output as a percentage. On California vehicles, the CIS-E control unit must be switched to output an on/off ratio before diagnosing vehicle using on/off ratio tester.

The CIS-E system 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), On/Off Ratio Tester (909 589 00 21 00), DVOM.


Mercedes-Benz 190E 1993 - RETRIEVING CODES


NOTE: On CIS-E vehicles, on/off ratio output is used to diagnose intermittent problems. On CIS-E California vehicles, Diagnostic Trouble Codes (DTCs) are used to diagnose hard failures.


Mercedes-Benz 190E 1993 - CIS-E


NOTE: On California vehicles, the CIS-E control unit must be switched to output on/off ratio before diagnosing vehicle using on/off ratio tester. If CIS-E control unit is not switched to output an on/off ratio, on/off ratio output will be wrong resulting in incorrect diagnosis.


Mercedes-Benz 190E 1993 - On/Off Ratio Output


  1. Turn ignition off. Perform pretest conditions. See PRETEST CONDITIONS. If diagnosing a Federal vehicle, go to step 3). If diagnosing a California vehicle, turn ignition on. Press non-locking switch, located on diagnostic connector in right rear corner of engine compartment, for 2-4 seconds. See Fig. 1 .
  2. CIS-E control unit will begin flashing LED light on diagnostic connector. See Fig. 1 . Wait for LED to stop flashing. When LED illuminates constantly, press non-locking switch again for 2-4 seconds. Pressing non-locking switch puts CIS-E control unit into on/off ratio output mode.

    Mercedes-Benz 190E 1993 - Component Locations - Connecting On/Off Ratio Tester https://portal-diagnostov.com/license.html
    https://portal-diagnostov.com/license.html Automotive Electricians Portal FZCO Automotive Electricians Portal FZCO
    Download PDF file
    Fig. 1: Mercedes-Benz 190E 1993 - Component Locations - Connecting On/Off Ratio Tester

    NOTE: Limited diagnostic information is available for 190E 2.6L.

  3. Connect On/Off Ratio Tester (909 589 00 21 00) to diagnostic connector located on left fender apron. See Fig. 1 . Start engine. Read on/off ratio. Turn ignition off. On 6-cylinder vehicles, see CIS-E (2.6L) under ON/OFF RATIO IDENTIFICATION. On 4-cylinder vehicles, before diagnosing on/off ratio readout, disconnect on/off ratio tester. Connect 25-Pin Test Cable (124 589 33 63 00) between CIS-E control unit and vehicle wiring harness.
  4. Connect Contact Box (124 589 00 21 00) to 25-pin test cable. See Fig. 2 . See ON/OFF RATIO DIAGNOSIS for testing. If no on/off ratio is output, see NO ON/OFF RATIO OUTPUT under ON/OFF RATIO DIAGNOSIS.

Mercedes-Benz 190E 1993 - Component Locations - Connecting Contact Box https://portal-diagnostov.com/license.html
https://portal-diagnostov.com/license.html Automotive Electricians Portal FZCO Automotive Electricians Portal FZCO
Get access to all wiring diagrams of the carDownload PDF file

Fig. 2: Mercedes-Benz 190E 1993 - Component Locations - Connecting Contact Box


Mercedes-Benz 190E 1993 - Diagnostic Trouble Code


  1. Turn ignition off. Perform pretest conditions. See PRETEST CONDITIONS. If using a pulse counter to diagnose vehicle, go to step 6). If pulse counter is not available, go to next step.
  2. If diagnosing California vehicle, turn ignition on. Press non-locking switch located on diagnostic connector in right rear corner of engine compartment for 2-4 seconds. See Fig. 1 .
  3. CIS-E 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.
  4. Press non-locking switch again for 2-4 seconds. If more fault codes are stored, LED on diagnostic connector will display next code. Continue pressing non-locking switch for 2-4 seconds at a time until LED lights steadily indicating end of fault code display.
  5. Record all fault codes. On 6-cylinder vehicles, see CIS-E FAULT CODE IDENTIFICATION to identify fault code. On 4-cylinder vehicles, see CIS-E FAULT CODE IDENTIFICATION to identify fault code and cross-over to an on/off ratio percentage for diagnosis. After crossing-over to an on/off ratio percentage, see ON/OFF RATIO DIAGNOSIS to diagnose vehicle.
  6. Connect Pulse Counter (124 589 19 21 00) to vehicle battery and diagnostic connector located in right rear corner of engine compartment. See Fig. 3 .

    Mercedes-Benz 190E 1993 - Component Locations - Connecting Pulse Counter https://portal-diagnostov.com/license.html
    https://portal-diagnostov.com/license.html Automotive Electricians Portal FZCO Automotive Electricians Portal FZCO
    Get access to all wiring diagrams of the carDownload PDF file

    Fig. 3: Mercedes-Benz 190E 1993 - Component Locations - Connecting Pulse Counter

  7. U-BATT LED on pulse counter display will illuminate if equipment is properly connected. If U-BATT LED illuminates, go to step 10). If U-BATT LED does not illuminate, check pulse counter fuse. Replace as necessary. If pulse counter fuse is okay, go to next step.
  8. 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.
  9. Using a DVOM, measure voltage between diagnostic connector terminals No. 1 and 3. Voltage should be .7-2.5 volts. If voltage is not .7-2.5 volts, repair wiring as necessary.
  10. 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.
  11. 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. On 6-cylinder vehicles, see CIS-E FAULT CODE IDENTIFICATION to identify fault code. On 4-cylinder vehicles, see CIS-E FAULT CODE IDENTIFICATION to identify fault code and cross-over to an on/off ratio percentage for diagnosis. After crossing-over to an on/off ratio percentage, see ON/OFF RATIO DIAGNOSIS to diagnose vehicle.

Mercedes-Benz 190E 1993 - CIS-E FAULT CODE IDENTIFICATION



Mercedes-Benz 190E 1993 CIS-E (2.3L) FAULT CODE IDENTIFICATION

Fault Code On/Off Ratio Percent
1 (1)
2 20
3 30
4 40
5 50
6 (2)
7 70
8 80
9 (3)
10 10
12 (4)
(1) No faults in. system.
(2) Not assigned.
(3) See NO ON/OFF RATIO OUTPUT, step 11).
(4) See EGR TEMPERATURE SENSOR in SENSOR RANGE CHARTS article in the ENGINE PERFORMANCE Section.


Mercedes-Benz 190E 1993 CIS-E (2.6L) FAULT CODE IDENTIFICATION

Fault Code Malfunctioning Component/System
1 (1)
2 Throttle Valve Switch (Full Throttle Contact)
3 Coolant Temperature Sensor
4 Airflow Sensor Potentiometer
5 Oxygen Sensor
6 (2)
7 TNA (Engine RPM) Signal
8 Altitude Pressure Signal From EZL Ignition Control Unit
9 Current To Electrohydraulic Actuator
10 Throttle Valve Switch (Idle Contact)
11 Air Injection System
12 Absolute Pressure Valves From EZL Ignition Control Unit
13 Intake Air Temperature Signal
14 Road Speed Signal At CIS-E Control Unit
15 (2)
16 Exhaust Gas Recirculation (EGR)
17 Oxygen Sensor Signal
18 Current To Idle Speed Air Valve
19 (2)
20 (2)
21 (2)
22 Oxygen Sensor Heating Current
23 Short Circuit To Positive In Regeneration Switchover Valve Circuit
24 (2)
25 Short Circuit To Positive In Start Valve Circuit
26 Short Circuit To Positive In Shift Point Retard Circuit
27 Data Exchange Fault Between CIS-E Control Unit and EZL Ignition Control Unit
28 Loose Contact In Coolant Temperature Sensor Circuit
29 Difference In Coolant Temperatures Between CIS-E Control Unit and EZL Ignition Control Unit
30 (2)
31 Loose Contact In Intake Air Temperature Sensor Circuit
32 (2)
33 (2)
34 Faulty Coolant Temperature Sensor Signal From EZL Ignition Control Unit
(1) No faults in system.
(2) Not assigned.


Mercedes-Benz 190E 1993 - CLEARING CODES CIS-E


  1. On Federal vehicles, disconnect vehicle battery. Stored codes are now erased. On California vehicles, disconnecting vehicle battery will not erase codes. Each code stored in CIS-E control unit must be erased individually. Start engine and idle. If using a pulse counter to diagnose vehicle, go to step 3). If pulse counter is not available, go to next step.
  2. If diagnosing a California vehicle, turn ignition on. Press non-locking switch, located on diagnostic connector in right rear corner of engine compartment, for 2-4 seconds. When fault is displayed, press non-locking switch for 6-8 seconds. Fault is now cleared. Continue procedure until all stored faults have been erased.
  3. 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 190E 1993 - ON/OFF RATIO IDENTIFICATION CIS-E (2.6L) On/Off Ratio Zero Percent


Check possible failures in order given:

  • No voltage or ground at diagnostic connector located on left fender apron.
  • Wiring between diagnostic connector and CIS-E control unit may have an open circuit.
  • On/off ratio tester may be faulty.
  • Air/fuel mixture may be too rich.

Mercedes-Benz 190E 1993 - On/Off Ratio 10 Percent


Check possible failures in order given:

  • Airflow sensor potentiometer may have incorrect polarity or is faulty (idle RPM may be fast).
  • Throttle valve switch connector may have incorrect polarity or full load contact is shorted.

Mercedes-Benz 190E 1993 - On/Off Ratio 20 Percent


Full load contact may have incorrect polarity or is faulty. On/off ratio of 20 percent is output when throttle valve switch is operated.


Mercedes-Benz 190E 1993 - On/Off Ratio 30 Percent


Check possible failures in order given:

  • Short circuit may be present between CIS-E control unit and coolant temperature sensor.
  • Coolant temperature sensor may be faulty.

Mercedes-Benz 190E 1993 - On/Off Ratio 40 Percent


Check possible failures in order given:

  • Open or short circuit may be present between CIS-E control unit and airflow sensor potentiometer.
  • Airflow sensor potentiometer may be faulty (idle RPM may be fast).

Mercedes-Benz 190E 1993 - On/Off Ratio 50 Percent


Check possible failures in order given:

  • Oxygen sensor may not be operational or faulty.
  • Oxygen sensor wiring may have an open circuit.

Mercedes-Benz 190E 1993 - On/Off Ratio 60 Percent


No road speed signal (speedometer) at CIS-E control unit. Road speed signal is only checked by CIS-E control unit when vehicle is moving. If an incorrect speed signal is detected, on/off ratio of 60 percent is output. If no speed signal is present, vehicle will jerk when moving with throttle valve closed.


Mercedes-Benz 190E 1993 - On/Off Ratio 70 Percent


Check possible failures in order given:

  • No engine speed (TNA) signal.
  • Open circuit to CIS-E control unit.

Mercedes-Benz 190E 1993 - On/Off Ratio 80 Percent


Check possible failures in order given:

  • Open or short circuit to ground for intake air temperature sensor.
  • Intake air temperature sensor may be faulty.
  • Malfunction in data interchange between CIS-E control unit and EZL ignition control unit.

Mercedes-Benz 190E 1993 - On/Off Ratio 85 Percent


On/off ratio readout of 85 percent means CIS-E control unit has the capability to output a pulse readout.


Mercedes-Benz 190E 1993 - On/Off Ratio 90 Percent


No current to electrohydraulic actuator.


Mercedes-Benz 190E 1993 - On/Off Ratio 95 Percent


On/off ratio readout of 95 percent means CIS-E control unit is in deceleration fuel shutoff mode.


Mercedes-Benz 190E 1993 - On/Off Ratio 100 Percent


Check possible failures in order given:

  • No voltage or ground at CIS-E control unit or CIS-E control unit is faulty.
  • Air/fuel mixture may be too lean.
  • Oxygen sensor may be faulty or shorted to ground.
  • Overvoltage protection relay fuse may be faulty.
  • On/off ratio tester may be faulty. On/Off Ratio Fluctuates

All monitored signals are functioning properly.