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Home >> Nissan-Datsun >> 1989 >> Sentra Hatchback Coupe L4-1597cc 1.6L SOHC (GA16i) >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Testing and Inspection >> Reading and Clearing Diagnostic Trouble Codes >> Clearing Diagnostic Trouble Codes >> Mode I and II (Mixture Feedback Test)

Mode I and II (Mixture Feedback Test)

The following procedure will describe inspection and adjustment of the mixture feedback system.
1. Start the engine and warm it up until the water temperature indicator points to the middle of the gauge.
2. Operate the engine at 2000 rpm for 2 minutes under no load.

Fig. 55 Inspecting E.C.U. Lamps:





3. Make sure that the green L.E.D. on the E.C.U. (located under the R.F. seat) flashes on and off more than 5 times in 10 seconds at 2000 rpm under no load.
a. If OK proceed to step 4. The O2 sensor is operating properly.
b. If not OK, turn the engine off and proceed to step 8.

Fig. 92 Throttle Sensor And Idle Switch:





4. Disconnect idle switch connector.
5. Race the engine 2 or 3 times then idle.

Fig. 52 Selecting Modes:





6. Turn the diagnostic mode selector on the E.C.U. fully clockwise and wait for the L.E.D.`s to flash 2 times, then immediately turn the selector counterclockwise. The ECCS system is now in "Mode 2".
7. Make sure that both L.E.D.'s flash simultaneously.
a. If OK, mixture feedback operation (air/fuel mixture) is correct proceed to step 36.
b. If not OK, turn the engine off and proceed to step 14.
8. Disconnect the battery ground cable.
9. Disconnect the ECU 20 pin connector.
10. Disconnect the O2 sensor terminal.

Fig. 148 O2 Sensor Harness Inspection:





11. Using a suitable jumper wire, connect the O2 sensor harness terminal to engine or body ground (not the O2 sensor's wire).
12. Using an ohm meter check for continuity between terminal 18 of the ECU harness and engine or body ground.
a. If continuity does not exist, check the harness for an open circuit and repair or replace harness as necessary.
b. If continuity does exist, proceed to step 13.
13. Reconnect the ECU harness (do not remove the jumper wire at the O2 sensor).
14. Disconnect the water temperature sensor harness connector. (Located at the front of the engine near the thermostat housing).
15. Connect a 2.5k ohm resistor to the harness connector.
16. Disconnect the AIV hose and plug the outlet.
17. Disconnect the AIV solenoid connector.
18. Reconnect the battery ground cable.
19. Start and warm the engine to operating temperature.
20. Using an exhaust gas analyzer, check the CO mixture at idle.
a. If CO is between 3% and 10% replace the O2 sensor and proceed to step 21.
b. If CO is not between 3% and 10 % proceed to step 26.
21. Reconnect the AIV hose and solenoid connector.
22. Remove the resistor from the water temperature sensor and reconnect the connector.
23. Start and warm the engine to operating temperature.
24. Operate the engine at 2000 rpm and confirm that the green diode on the ECU flashes more than 5 times in 10 seconds.
a. If OK, proceed to step 4.
b. If not OK, perform MODE 3 (STORED CODES) TEST and repair any codes stored in memory.

Fig. 65 Air/Fuel Mixture Adjusting Screw:





25. Remove the throttle body from the engine.
26. Drill out and remove variable resistor plug.
Warning: Do not damage air flow meter or allow shavings to contaminate passages when drilling.
27. Install throttle body with new gasket.
28. Start the engine and warm it up until the water temperature indicator points to the middle of the gauge.
29. Operate the engine at 2000 rpm for 2 minutes under no load.
30. Race the engine 2 or 3 times then idle.
31. Turn the diagnostic mode selector on the E.C.U. fully clockwise and wait for the L.E.D.`s to flash 2 times, then immediately turn the selector counterclockwise. The ECCS system is now in "Mode 2".

Fig. 55 Inspecting E.C.U. Lamps:





32. Adjust air/fuel mixture ratio by turning variable resistor in air flow meter so that both L.E.D.'s on the E.C.U. flash simultaneously at 2000 rpm.
a. If OK proceed to step 17.
b. If not OK, proceed to step 20.
33. Turn the engine off. This will return the ECCS system to "Mode 1" (normal operating mode).
34. Remove throttle body from the engine and install a new plug over the variable resistor screw.
35. Install throttle body with new gasket.
36. Turn the engine off. Turning the engine off will return the ECCS system to Mode 1 (normal operating mode).

Fig. 100 Kick-Down Adjustment:





AUTOMATIC TRANSMISSION KICKDOWN CABLE ADJUSTMENT PROCEDURE.
1. Loosen kickdown cable locknuts on throttle body.
2. Open throttle valve to "P1" position (full throttle).
3. Pull fitting "Q" in direction "T" and turn nut "B" in direction "U" until it contacts cable bracket on throttle chamber.
4. Back off nut "B" 1.0 to 1.5 revolutions.
5. Tighten nut "A" securely.
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