Diagnostika OBD1 Mercedes

Mercedes Code Retrieval

Accessing Diagnostic Trouble Codes

With Impulse Counter

  • With ignition switch On and shift lever in P/N position, connect impulse counter.
  • Depress Start button for at least two seconds but no more than four seconds, read codes.
  • Read codes until first code displayed appears again.
  • Codes will appear in ascending order.

With On-Off Ratio Readout

  • On models equipped with on board diagnostics, depress non-locking switch to convert control unit to read on-off readout ratio codes.
  • On all models, install on-off readout ratio tester to diagnostic socket.
  • Allow engine to idle and oil temperature to reach 140-176�F (60-80�C).
  • Read and record on-off readout ratio codes.

With Scan Tool

A hand-held tester can be connected to the underhood data link connector (DLC) X11/4 located at module box, or a generic scan tool can be connected to the generic connector X11/22 located in the tower edge of the instrument panel. To access diagnostic trouble codes, follow the tool manufacturer's instructions.

Clearing Diagnostic Trouble Codes

With Impulse Counter

    • Complete required repairs resulting from recorded codes.
    • With impulse code displayed, wait two seconds then depress Start button for at least six seconds.
    • Each code must be erased individually.
    • If no number is displayed, then diagnostic trouble codes are erased from memory.
    • If code higher than one appears, codes are still stored in memory.

With Scan Tool

To clear DTC's, follow the scan tool manufacturer's instructions.

Diagnostic Codes


90-93 190E - 300 series (2.3L)
1 No system malfunction.
2 Throttle valve switch.
3 Coolant temp sensor.
4 Airflow sensor position indicator.
5 Oxygen sensor.
6 Not used.
7 Td signal.
8 Altitude correction capsule.
9 Electro-hydraulic actuator (EHA).
10 Throttle valve switch and/or Idle speed contact.
11 Not used.
12 EGR temp sensor.


91 - later 300 series (2.8L and 3.2L)
1 No faults.
2 Oxygen sensor inoperative.
3 Lambda control inoperative.
4 Air injection inoperative.
5 EGR inoperative.
6 Idle speed control inoperative.
7 Ignition system failure.
8 Coolant temp sensor-open or short circuit.
9 Intake air temp sensor-open or short circuit.
10 Voltage at Air Mass sensor too high or low.
11 TN (RPM) signal defective.
12 Oxygen sensor heater open or short circuit.
13 Cam position sensor signal from-EZL/AKR ign. control unit defective.
14 Intake manifold pressure at start too low.
15 Full throttle Info defective.
16 Idle speed info defective.
17 CAN Data exchange-Malfunction between control units.
18 Adjustable camshaft timing solenoid-open or short circuit.
19 Fuel injectors-open or short circuit or Emission control system adaptation at limit.
20 Speed signal missing.
21 Purge switchover valve-open or shorted.
22 cam position sensor signal defective.
23 Intake manifold pressure w/ engine running too low.
24 Starter ring gear segments defective.
25 Knock sensors.
26 Upshift delay switch over valve-open or shorted.
27 Coolant temp sensor deviation between sensor ciruits 1 - 2.
28 Coolant temp Sensor.


91-93 190E and 300 series (2.6L and 3.0L)
1 No faults in system.
2 Throttle valve switch(full throttle contact).
3 Coolant temp sensor.
4 Airflow sensor potentiometer.
5 Oxygen sensor.
7 TNA (RPM) signal.
8 Altitude pressure signal from EZL Ignition control unit.
9 Current to Electro-hydraulic actuator.
10 Throttle valve switch(idle contact).
11 Air injection system.
12 Absolute pressure valves from ELZ ignition control unit.
13 Intake air temp signal.
14 Road speed signal at CIS-E control unit.
16 EGR.
17 Oxygen sensor signal.
18 Current to idle speed air valve.
22 Oxygen sensor heating current.
23 Short to positive in regeneration switch over valve circuit.
25 Short to positive in start valve circuit.
26 Short 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 temp sensorcircuit.
29 Difference in coolant temps between CIS-Eunit and EZL unit.
31 Loose contact in intake air temp sensor circuit.
34 Faulty coolant temp sensor signal from EZL unit.