Volkswagen Golf/Jetta/Cabriole 1990-1999

Diagnosis and Testing


Before beginning any diagnosis and testing procedures, visually inspect the components of the ignition system and engine control systems. Check for the following:

Discharged battery
Damaged or loose connections
Damaged electrical insulation
Poor coil and/or spark plug connections
ECM connections
Blown fuses
Damaged spark plugs

When attempting to search for ignition troubles, also keep in mind that various sensor inputs which the ECM uses to calculate timing may affect engine performance.

Ignition system Precautions

Before proceeding with any type of ignition system testing, be sure to follow these important precautions:

Make sure the ignition switch is OFF before connecting or disconnecting any wiring or test equipment.
When cranking the engine without starting, as for a compression test, disconnect the power supply connector (+12V) from the coil to prevent it from receiving voltage. Other methods of disabling the ignition system are not recommended, and may result in electrical system damage.
Always switch the multimeter to the appropriate measuring range BEFORE making the test connections. Use a high-impedance digital multimeter which is designed for testing computerized electrical components.
DO NOT install a standard ignition coil in the system.
DO NOT connect a condenser/suppressor or powered test light to the negative terminal (1) of the ignition coil.
DO NOT connect any 12-volt test instruments to the positive terminal (15) of the ignition coil. The electronic control unit will be permanently damaged.
DO NOT use a standard test light (electric bulb type) on electronic circuits. The high electrical consumption of these test lights can lead to electronic component damage.
DO NOT connect a quick-charger to the battery for more than 1 minute, nor exceed 16.5 volts with the booster.

Secondary Spark Test

Refer to testing under distributor ignition system in this section.