Without VAG
WIRING CHECKDigifant I 38 Pin Control Unit Connector:
1. With the ignition "OFF", disconnect the Motronic control unit harness connector. The Motronic 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 Position Sensor harness connector, which is located on the throttle body.
3. Using a suitable digital multimeter set on ohms, measure the resistance between Motronic harness connector pin 34 and Throttle Position Sensor 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 Motronic harness connector pin 33 and Throttle Position Sensor harness connector pin 2:
^ The correct measurement should be continuity (1.5 ohms maximum).
5. Measure the resistance between Motronic harness connector pin 28 and Throttle Position Sensor harness connector pin 3:
^ The correct measurement should be continuity (1.5 ohms maximum).
If continuity is not present the Throttle Position Sensor harness is open. Repair or replace as necessary. If all measurements are correct, continue with test procedure.
6. Check for proper cable routing.
VOLTAGE CHECK
1. With the ignition "OFF", reconnect the Motronic control unit harness connector to the control unit and reconnect harness connector to the Throttle Position Sensor.
2. Remove cover from back of Motronic 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 Motronic 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 Motronic control unit harness connector
9. If the last two voltage readings are out of specification, Throttle Position Sensor is faulty.
NOTE: Because of its adaptive capability, the Motronic control unit MUST be returned to its reference settings IF:
1. The Engine Coolant Temperature Sensor (blue connector) has been disconnected while the engine is running.
2. Any of these components have been replaced:
^ Motronic control unit
^ Mass Air Flow Sensor
^ Throttle Position Sensor
^ Throttle body