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Trouble Shooting

TROUBLE SHOOTING - IGNITION ON, ENGINE OFF

On-Off Ratio % Readout Malfunction Test Step
0 Not Used Not Used
10 Throttle Valve Switch Idle Contacts Open 10.0-10.3
20 Throttle Valve Switch Full Load Contacts Closed 5.0-5.3
30 Coolant Temp. Not Between 158°-212°F (70°-100°C) 6.0-6.3
40 Airflow Sensor Plate Deflected 7.0-7.6
50 Input Signals In Order N/A
60 Speed Signal Recognized 11.0-11.2
70 Starter Signal Circuit No. 50 Recognized 20.0
80 Drive Position Selected N/A
90 Current at EHA Unlikely 4.0-4.4
100 Not Used N/A
COOLANT TEMPERATURE SENSOR SPECIFICATIONS

°F (°C) Ohms Volts at Socket
-4 -(20) 15,700 3.24-3.94
14 (-10) 9200 2.84-3.47
32 (0) 5900 2.39-2.93
50 (10) 3700 1.94-2.37
68 (20) 2500 1.51-1.84
86 (30) 1700 1.16-1.42
104 (40) 1180 0.88-1.08
122 (50) 840 0.66-0.80
140 (60) 600 0.50-0.61
158 (70) 435 0.38-0.46
176 (80) 325 0.29-0.35
194 (90) 247 0.22-0.26
MALFUNCTION DIAGNOSTIC CODES (IMPULSE READOUT OF CIS-E CONTROL UNIT)

Code No. Malfunction Test Step Possible Cause
1 No System Malfunction N/A N/A
2 TV Switch Contacts-Full Load 5.0-5.3 Short in ckt 31
3 Coolant Temp. Sensor 6.0-6.3 Short in ckt 15, 30, &/or 31
4 Airflow Sensor Position Indicator 7.0-7.6 Short in ckt 15, 30, &/or 31
5 Oxygen Sensor 14.0-14.3 N/A
6 Not Used Not Used Not Used
7 NA Signal (RPM) 8.0-8.1 Open ckt
8 Altitude Pressure Signal Vacuum Line or EZL Control Unit
9 Electro-Hydraulic Actuator (EHA) 4.0-4.4 Short in ckt 15, 30, &/or 31
10 TV Switch-Idle Contacts 10.0-10.3 Short in ckt 31
11 Air Injection System 16.0-16.4 Pneumatic
12 Absolute Pressure Values From EZL Control Unit Vacuum line or EZL Control Unit
13 Intake Air Temp. Sensor 13.0-13.3 Short in ckt 15, 30, &/or 31
14 Speed Signal Sensor 11.0-11.2 Short in ckt 15, 30, &/or 31
15 Not Used Not Used Not Used
16 EGR 21.0-22.2 Electric/Pneumatic
17 O2 Sensor Wire Shorted to B+ or Ground 14.0-14.3 Short in ckt 15, 30, &/or 31
18 Idle Speed Air Valve 18.0-18.3 Short in ckt 15, 30, &/or 31
19 Not Used Not Used Not Used
20 Not Used Not Used Not Used
21 Not Used Not Used Not Used
22 O2 Sensor Heating Current 14.4-14.8 N/A
23 Purge Switchover Valve Shorted to B+ 19.1-19.4 Short in ckt 15, &/or 30
24 Not Used Not Used Not Used
25 Start Valve Shorted to B+ 17.0-17.2 Short in ckt 15, &/or 30
26 Shift Point Delay Shorted to B+ N/A N/A
27 Data Exchange Between CIS-E Control Unit & EZL Control Unit Interrupted 12.0 Check if control units are compatible
28 Coolant Temp. Sensor Intermittent N/A Repair wiring or unit
29 CIS-E & EZL control units read different temperature 6.0-6.3 Check CTS ckt to EZL
30 Not Used Not Used Not Used
31 Intake Air Temp. Intermittent N/A Repair wiring or replace unit
32 Not Used Not Used Not Used
33 Not Used Not Used Not Used
34 EZL control unit reading unlikely temp. N/A Short in ckt 15, 30, &/or 31, or CTS ckt shorted to EZL
TROUBLE SHOOTING - ENGINE AT IDLE

On-Off Ratio % Readout Malfunction Test Step
0 Open in ground ckt at diagnostic connector pin socket No. 2. Open ckt in wire to diagnostic connector pin socket No. 3 or No. 6, or on-off ratio tester is defective. Mixture adjustment possibly too rich. (1) Repair as necessary
10 Airflow sensor position indicator polarity reversed or defective 7.0-7.6
10 Connector terminals of throttle valve switch reversed (idle and full load contacts) 5.0-5.3
10 Idle contacts open with microswitch closed 10.0-10.3
20 Full load contacts defective or throttle valve switch polarity reversed 5.0-5.3
20 20% is displayed only when microswitch activated Repair as necessary
30 Short or open ckt between CIS-E control unit and coolant temp. sensor 6.0-6.3
30 Defective coolant temperature sensor, or excessive deviation in temperature values in comparison with EZL ignition control unit Repair as necessary
40 Open or short in airflow sensor position indicator wiring, or defective airflow sensor position indicator 7.0-7.6
50 O2 sensor not operational or defective, or open in ckt 14.0-14.3
60 Unlikely speed signal at CIS-E control unit 11.0-11.2
70 Unlikely TNA-signal (RPM) at CIS-E control unit 8.0-8.1
80 Interrupted data exchange between EZL ignition control unit & CIS-E control unit 12.0
90 Unlikely current reading at EHA 4.0-4.4
95 Deceleration fuel shut-off valve in operation Repair as necessary
100 No voltage or ground at CIS-E control unit, or CIS-E control unit defective, or On-off ratio tester defective 1.0-3.0
100 Lambda adjustment too lean. O2 sensor defective (short to ground). 14.0-14.7 Needle Oscillates. No malfunctions of signals monitored N/A
(1) Check fuse No. 9 to be defective.
Fig 1: Tester Connections (190E & 300 Series Except 300SE & 300SEL)
G91F17454Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Fig 2: Tester Connections (300SE & 300SEL, 420SEL & 560 Series)
G91G17455Courtesy of MERCEDES-BENZ OF NORTH AMERICA.