California Vehicles (Digifant I)
WIRING CHECKDigifant I 38 Pin Control Unit Connector:
1. With the ignition "OFF", disconnect the Digifant control unit harness connector. The Digifant control unit is located beneath the drip tray, at the left rear (drivers side) of the engine compartment. For these tests it may be easier to remove the control unit from its mount, this will allow better access to the harness connector pins.
Special Tools:
CAUTION: Avoid damaging the delicate connectors within the control unit harness connector. A simple set of test leads can be fabricated using flat connectors (part # VW N 17 457 2) or equivalent, and a pair of alligator clips.
Digifant I Throttle Valve Potentiometer:
2. Disconnect throttle valve potentiometer harness connector, which is located on the throttle body.
3. Using a suitable digital multimeter set on ohms, measure the resistance between Digifant harness connector pin 34 and throttle valve potentiometer harness connector pin 1:
^ The correct measurement should be continuity (1.5 ohms maximum).
CAUTION: Always turn the ignition switch "OFF" before changing meter ranges, and before disconnecting or connecting the meter probes. Doing so with the ignition switch turned "ON" risks permanent control unit damage.
4. Measure the resistance between Digifant harness connector pin 33 and throttle valve potentiometer harness connector pin 2:
^ The correct measurement should be continuity (1.5 ohms maximum).
5. Measure the resistance between Digifant harness connector pin 28 and throttle valve potentiometer harness connector pin 3:
^ The correct measurement should be continuity (1.5 ohms maximum).
If continuity is not present the throttle valve potentiometer harness is open. Repair or replace as necessary. If all measurements are correct, continue with test procedure.
VOLTAGE CHECK
1. With the ignition "OFF", reconnect the Digifant I control unit harness connector to the control unit and reconnect harness connector to the throttle valve potentiometer.
2. Remove cover from back of Digifant control unit harness connector allowing access to back of control unit connector pins. Be sure exposed connector pins do not touch any metal surfaces while back cover is off.
3. Turn ignition switch "ON".
4. Using a suitable digital volt meter set on the 20-volt DC scale, carefully probe the back of control unit connector pins as follows. Be sure of pin number before probing with meter lead.
Digifant I 38 Pin Control Unit Connector:
5. With NEGATIVE (black) meter lead, probe control unit connector pin 28. With POSITIVE (red) meter lead, probe control unit connector pin 34.
^ The correct measurement should be 4.5 to 5.5 volts DC. If voltage reading is incorrect Digifant control unit may be faulty.
6. With NEGATIVE (black) meter lead, probe control unit connector pin 28. With POSITIVE (red) meter lead, probe control unit connector pin 33.
^ The correct measurement should be 0.3 to 1.7 volts DC with throttle in closed (idle) position.
7. With NEGATIVE (black) meter lead, probe control unit connector pin 28. With POSITIVE (red) meter lead, probe control unit connector pin 33.
^ The correct measurement should be 3.0 to 5.0 volts DC with throttle in wide open (full throttle) position.
8. Turn ignition switch "OFF". Reattach cover to back of Digifant control unit harness connector
9. If the last two voltage readings are out of specification, throttle valve potentiometer is faulty.
NOTE: Because of its adaptive capability, the Digifant I control unit MUST be returned to its reference settings IF:
1. The coolant temperature sensor (blue connector) has been disconnected while the engine is running.
2. Any of these components have been replaced:
^ Digifant I control unit
^ Air flow sensor
^ Throttle valve potentiometer
^ Throttle body
Refer to RESETTING DIGIFANT I CONTROL UNIT. Resetting Digifant I Control Unit