Important vehicle information

• Always turn off the ignition or disconnect the battery for resistance tests (if this is not done, the measuring device may be destroyed).

• Always disconnect the speed sensor plug for compression tests. (If this is not done, dangerous high voltages and insulation damage to the ignition coil, high-voltage distributor and ignition leads may result. In addition, the remaining spark plugs of the 2nd ignition circuit could ignite.)

• The specified ignition coil (refer to Order No.) must not be replaced by a different Ignition coil.

• Never connect a suppression capacitor to ignition coil terminals 1 and 15.

• Never connect ignition coil terminal 1 to ground for the burglar alarm. (The ignition coil and control unit could be destroyed.)

• Never connect battery plugs or a test lamp to ignition coil terminal 1 (the control unit will be destroyed).

• Never disconnect the ignition lead from ignition coil terminal 4 to high-voltage distributor terminal 4 during operation.

• Voltage flashover from ignition coil terminal 4 to ignition coil terminals 1 and 15 must not occur. (The control unit could be destroyed.)

• In order to avoid destruction of the control unit, the secondary circuit of the ignition system must be suppressed with at least 4 kii, whereby the original distributor rotor with 1 kQ suppression resistance must be installed.

• Disconnect the DME control unit and ignition output stage plugs only after turning off the ignition.

• Flashover or distructive discharge in the area of the high-voltage distributor cap (poor insulation) could destroy the control unit.

• Never disconnect the battery when the engine is running.

• Battery polarity reversal could lead to destruction of the ignition output stage, ignition coil and DME control unit.

• External engine starting with more than 16 V or with a boost battery charger is forbidden.

• Always follow the accident prevention regulations when working on the fuel system.

OA/O fi 911 Carrera 2

^H"/ ^O Fuel System - Electronic Control 911 Carrera 4

Equipment required for DME testing:

Diagnostic tester 9288 (9268) with connecting leads

1 oscilloscope approved by Porsche

1 digital display multimeter, internal resistance min. 10 M£2

1 Bosch L-Jetronic test lead, Bosch No. 1684 463 093 (Check leads for correct polarity in plugs.)

2 control units plug test leads (self-manufactured) equipped with 2 tab connectors No. 17.457.2 in order to avoid damage to the plug contacts in the control unit plug during testing.

2 adapter test leads, consisting of: 4 plug connectors N 017.483.1 with 2 leads ap-prox. 150 mm long, soldered.

2 control unit plug test leads (self-manufactured) equipped with 4 tab connectors N 17.457.2.

The test leads must be used under all circumstances in the tests!

All sensor and ignition timing signals of Porsche vehicles can be checked with the engine testers recommended by Porsche. Since there are different instructions for the tester connections to the vehicle, depending on the manufacturer in question, these instructions must always be followed to ensure correct tester connection.

The following sensor signals can be checked with an oscilloscope:

Speed sensor signal

- ti signals

Idle speed control activation signal Hall sensor signal

Ignition trigger signal to ignition output stage

- Tank venting activation signal Activation signal for resonance plate as well as:

Reed switch signal (speedometer) ABS wheel sensor signals

911 Carrera 2

911 Carrera 4 Fuel System - Electronic Control

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