CIS-E Motronic

Testing Hall Sender and Coil Power Stage (CIS-E Motronic only)
The Hall sender and coil power stage should be tested if there is no spark at the spark plugs when tested. These tests so check the Motronic control unit's response to the Hall sender signal. For these tests, the spark plug wires and ignition coil should be in good condition as described in Testing Coil and Spark Plug Wires. The Hall sender connector is on the side of the distributor. The coil power stage is located next the coil.

These tests require the use of a high-impedance voltmeter low-current LED test light. For more information, Basic Troubleshooting Principles. The sequence of the tests below is important. Follow the test sequence as it is presented order to logically isolate the faulty component.

CAUTION: Always turn the ignition OFF before connecting or disconnecting ignition test equipment. Switch multimeter functions or measurement ranges only with the test probes disconnected.

Voltage Supply and Ground to Power Stage
Begin testing by checking the power stage. With the ignition OFF, disconnect the power stage harness connector. Connect a voltmeter to terminals 1 and 3 as shown in Fig. 3-11. When the ignition is turned ON, there should be approximately battery voltage. Turn OFF the ignition. If there is no voltage, either there is a break in the wiring from terminal 1 to the fuse relay panel, or from terminal 3 to ground. Use the wiring diagrams to check for continuity. Repair any wiring breaks as necessary, then reconnect the power stage connector.

Fig. 3-11:

Fig. 3-11. Voltage and ground to power stage heing checked at terminals 1 and 3 of connector. Volkswagen special tools shown.

Voltage Supply and Ground to Hall Sender
With the ignition OFF, disconnect the Hall sender harness connector. Using a voltmeter, check for voltage between the outer terminals as shown in Fig. 3-12. When the ignition is turned ON, there should be a minimum of 9 volts. Turn oft the ignition. If there is no voltage, check for continuity in the wiring between terminal 3 of the Hall sender connector and terminal 30 of the Motronic control unit connector, and between terminal 1 of the Hall sender connector and ground. Repair any breaks as necessary, then reconnect the Hall sender harness connector.

Fig. 3-12:

Fig. 3-12. Checking voltage supply at Hall sender connector (shown schematically).

Hall Sender Switching Function
Peel back the protective rubber boot on the Hall sender harness connector and connect an LED test light between the center terminal and the battery positive (+) terminal. See Fig. 3-13. Remove the coil wire from the center of the distributor and connect it to ground with a jumper wire. When the starter is actuated, the LED should flicker. If there is no reaction, the Hall sender is defective and should be replaced as described in Disassembling and Assembling Distributor.

Fig. 3-13:

Fig. 3-13. Hell sending unit switching function being tested using LED test light Volkswagen special tools shown.

Motronic Control Unit Response to Hall Sender Signal
Remove the wiring connector from the power stage and connect an LED test light between terminals 2 and 3 of the connector as shown in Fig. 3-14. With the Hall sender wiring connector connected and the coil wire still grounded, actuate the starter. The test light should flicker. If it doesn't, then either the wiring between terminal 2 of the power stage connector and terminal 11 of the control unit connector is faulty, or the Motronic Control Unit is faulty.

Fig. 3-14:

Fig. 3-14. Checking Motronic control unit signal to coil power stage with test light between terminals 2 and 3 of Power stage connector.

Power Stage Response to Motronic Control Unit Signal
Reconnect the power stage connector, then disconnect the Hall sender connector and attach a voltmeter to terminals 1 and 15 of the coil as shown in Fig. 3-15.

Fig. 3-15:

Fig. 3-15. Test set up for measuring voltage at ignition coil terminals.

Turn the ignition ON and, using a jumper wire, briefly connect the center terminal of the Hall sender connector to ground, as shown in Fig. 3-16. The voltage should briefly increase to at least 2 volts then drop to zero. If it doesn't, then either the power stage or the Motronic control unit is defective.

Fig. 3-16:

Fig. 3-16. Center terminal of Hall sender connector being briefly connected to ground to test Motronic control unit and power stage response.