California Vehicles (Digifant I)
NOTE: If the the throttle valve potentiometer is misadjusted, the engine may surge at idle or cutout during a steady driving speed or light throttle applications.The throttle valve basic adjustment must be OK for this adjustment to be valid. Refer to FUEL SYSTEMS.
PRE-ADJUSTMENT CHECKS
1. With the ignition "OFF", locate the Digifant control unit harness connector. The Digifant I control unit is located at the left rear of the engine compartment under the drip tray. 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.
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/ohm 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 (brown/white wire). With POSITIVE (red) meter lead, probe control unit connector pin 34 (blue/black wire).
^ The correct measurement should be 4.5 to 5.5 volts. If voltage reading is incorrect Digifant control unit may be faulty.
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.
6. With NEGATIVE (black) meter lead, probe control unit connector pin 28 (brown/white wire). With POSITIVE (red) meter lead, probe control unit connector pin 33 (red/blue wire).
^ The correct measurement should be 3.0 to 5.0 volts with throttle in wide open (full throttle) position.
7. With NEGATIVE (black) meter lead, probe control unit connector pin 28 (brown/white wire). With POSITIVE (red) meter lead, probe control unit connector pin 33 (red/blue wire).
^ The checking measurement should be 0.3 to 1.7 volts with throttle in closed (idle) position.
8. If the last two voltage readings are within specifications, adjust throttle valve potentiometer as follows.
ADJUSTMENT PROCEDURE
Digifant I Throttle Valve Potentiometer:
1. Remove intake air hose from throttle body inlet as needed for access to throttle valve potentiometer mounting/adjusting screws.
2. Connect voltmeter as in step 7 above, negative meter lead to pin 28, positive meter lead to pin 33. Obtain closed throttle (idle) voltage reading on meter as in step 7, (0.3 - 1.7 volts).
3. Loosen throttle valve potentiometer mounting/adjusting screws. While watching voltmeter reading, rotate potentiometer until 1.0 volts is obtained then tighten adjustment screws.
4. Slowly move the throttle valve several times throughout its range while watching meter reading, voltage should rise and fall smoothly with throttle valve movement.
5. Let throttle valve return to closed (idle) position. Recheck meter reading, it should still be 1.0 volts.
6. If closed throttle meter reading has changed repeat the steps above until reading stays constant, (try to get meter reading of exactly 1.0 volts, however small deviations are acceptable).
7. Turn ignition switch "OFF". Reattach cover to back of Digifant control unit harness connector and return control unit to its mount. Reattach intake air hose to throttle body if removed.
8. Check for any fault codes and erase as needed, refer to DISPLAYING FAULT CODES for procedure.
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.