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3.5 Digifant II and Digifant I Troubleshooting

This information applies to troubleshooting the fuel injection functions of the Digifant II and Digifant I engine management systems. For applications information, see 1.6 Applications-Identifying Features. For information on troubleshooting Digifant ignition functions, see IGNITION. The oxygen sensor system is covered in EXHAUST SYSTEM AND EMISSION CONTROLS. For troubleshooting other fuel injection systems, see 3.2 CIS Troubleshooting or 3.3 CIS-E and CIS-E Motronic Troubleshooting.

Some 1990 California models with Digifant II, and all 1991 and later models with Digifant I, feature an on-board fault diagnosis system which can record and display information on component faults in the engine management system. The first step in troubleshooting these systems should be to read the fault codes which are stored in the Digifant control unit memory. For more information, see 7.7 Digifant II On-Board Fault Diagnosis (California only), or 8.1 Digifant I On-Board Fault Diagnosis.

The basic factors of engine idle speed, ignition timing, and idle mixture (% CO) are critical, as they affect all other aspects of Digifant system performance. Before making any other adjustments to the system, make certain that these factors are within specifications. See 7.3 Idle Speed and 7.6 Idle Mixture Specifications (% CO) (Digifant II), or 8.5 Idle Speed and Mixture (% CO) Adjustment (Digifant I), and IGNITION.

Table d lists symptoms of Digifant fuel system problems, their probable causes, and suggested corrective actions. The boldface numbers in the corrective action column indicate the heading in this section of the manual where the applicable test and repair procedures are found.


Volkswagen specifies that the first step in troubleshooting any Digifant system with OBD must be to check the OBD fault memory, and to find and correct any faults that may be indicated.


To prevent cold-starting difficulties in below-freezing temperatures, depress the accelerator pedal slightly, switch the ignition on only once and crank the engine until it starts. Operating the ignition switch two or more times in succession will flood the engine.

Table d. Digifant II and Digifant I Troubleshooting

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