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Diagnostic Manual, Engines, Volume 2

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 1.1  HFM Sequential Multiport Fuel Injectin/Ignition System (HFM-SFI)   >   22 Electrical Test Program - Preparation for Test

Electrical Test Program - Preparation for Test

Preliminary work: Diagnosis - Malfunction Memory 11

Preparation for Test
1. Ignition: OFF
2. Connect test cable with socket box to engine control module (N3/4) according to connection diagram.

Electrical wiring diagrams, see Electrical Troubleshooting Manual.

Model 124
Model 129
Model 140
Model 202
Model 210

If installing an engine control module from another vehicle (only possible on vehicles without drive authorization system (DAS) stage 2 up to the end of model year 1995), the control module's memory must be erased and the control module must be reactivated, see 11 /5.

Note regarding "Test Connection" column:
The numbers indicated in parentheses, for example, 1.0 (1.23) signify:
1= Connector 1 on wiring diagram,
23= Socket 23 on wiring diagram.

Conventional tools, test equipment

Description Brand, model, etc.
Multimeter 1) Fluke models 23, 83, 85, 87
Engine analyzer 1) Bear DACE (Model 40-960)
Sun Master 3
Sun MEA-1500MB
1) Available through the MBUSA Standard Equipment Program.

To Avoid Damage to the Ignition System
To avoid damage to the engine control module (N3/10), connect/disconnect the control module connectors only with the
ignition: OFF .
Do not connect a test lamp to circuit 1 or 15 of the ignition coil.
Do not disconnect or ground any spark plug connector at cranking or idle speed.
The high output side of the ignition system must carry at least 2 k of load (spark plug connector).
To avoid damaging the ignition coils during individual testing, do not load the coil with more than 28 kV.
If assisting a disabled vehicle and it becomes necessary to perform an ignition spark test, perform this test only with a spark plug on one ignition cable. Ensure good ground connection to the spark plug.

High Voltage!

Primary connections carry a voltage of up to 400 V. The iron core bracket of the ignition coils must always be connected to vehicle ground.
Persons with pacemakers should not work on this type of ignition system.

Using Test Equipment
Ensure that the engine and ignition are turned off when connecting/ disconnecting equipment such as voltage signal pick-up on respective ignition cables and trigger pick-up on cylinder 1.

See Service Microfiche System (SMS), Repair Instructions, group 15 for further safety precautions.