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Originally Posted by 88pathoffroad
Sometimes the O2 sensor will cease to work but not throw an error code, but new ones are expensive so I wouldn't just replace it for no reason. I think there is a mixture adjustment screw on the back or top of your ECU(only came on 86-87 ECU's), but I don't have the procedure they used to test or tune it, sorry. Perhaps messing with that a little at a time would get you somewhere.
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Thanks this is getting wierd. We got it started and it did throw a ox code. replace the ox sensor. cleaned plugs started angain and then flooded loaded with carbon and quit.
Then saw this:
How to pull ECU error codes for 87-95 Pathfinders and hardbody pickups:
The ECU is under your passenger's side seat. You can gain access to it by simply sliding the seat all the way forward and removing the plastic cover from the ECU. You can also remove the seat if you want, it makes access a little easier.
The early VG30E and VG30i ECU's have a tiny toggle switch on the side of the ECU with a small snap-in switch cover that must be utilized to select the diagnostic mode of the ECU. The 4-cylinder ECU has a slotted switch that turns 1/4 or 1/2 turn clockwise and counterclockwise to do the same task.
Seat removed; ECU in place on the floor with cover. The cover has ONE screw holding it down. Remove that and the cover will pull off.
Diagnostic selector switch with switch cover removed and set on top of the ECU.
This is where the LED lights are visible on top of the ECU.
For V6:
1. Turn the ignition switch on, but do not start the engine. All of the lights in the dash should be on. OK
2. There is a little plastic tab you pull off of the side of the ECU(facing the door). A small toggle switch is behind it with 2 positions, "ON" and "DIAGNOSTICS". Using a small screwdriver or tool, move it to the diagnostics position. The red and green LED's on top of the ECU will blink simultaneously. One time, pause, then 2 times, three times, pause...so on for each mode, 1 through 5. Mode 3 is the most commonly used mode and will yield the ECU trouble codes you need to figure out what's going on with your engine.- NOPE don.t happen. off red green on, turn switch to on shows shows codes
3. After it blinks both LED's 3 times move the toggle switch back to the on position. After about five seconds it will start to output out the diagnostic codes as with the 4-cylinder ECU. Note each code as it is displayed, the red LED flashing once for 10's, and the green LED flashing once for 1's. Meaning: One red flash and two green flashes means code 12. NOPE don't happen turn switch to on then shows codes.
4. To clear the ECU of any trouble codes, move the switch to the "DIAGNOSTICS" position then back to the "ON" position and turn off the key. - "did not clear" on to off
1986.5-1995 Nissan ECU Flash Codes(all engines)
11 Crank Angle Sensor/Camshaft Position Sensor.
12 Air Flow Meter/Mass Air Flow Sensor.
13 Engine Coolant Temperature Sensor.
14 Vehicle Speed Sensor.
21 Ignition Signal.
22 Fuel Pump.
23 Idle Switch.
24 Throttle Valve Switch.
25 Idle Speed Control Valve.
28 Cooling Fan Circuit.
31 ECM.
32 EGR Function.
33 Heated Oxygen Sensor.
34 Knock Sensor.
35 Exhaust Gas Temperature Sensor.
36 EGR Control-Back Pressure Transducer.
37 Knock Sensor.
38 Right hand bank Closed Loop (B2).
41 Intake Air Temperature Sensor.
42 Fuel Temperature Sensor.
43 Throttle Position Sensor.
44 ECCS Normal Operation.
45 Injector Leak.
47 Crankshaft Position Sensor.
51 Injector Circuit.
53 Oxygen Sensor.
54 A/T Control.
55 No Malfunction.
63 No. 6 Cylinder Misfire.
64 No. 5 Cylinder Misfire.
65 No. 4 Cylinder Misfire.
66 No. 3 Cylinder Misfire.
67 No. 2 Cylinder Misfire.
68 No. 1 Cylinder Misfire.
71 Random Misfire.
72 TWC Function right hand bank.
73 TWC Function right hand bank.
76 Fuel Injection System Function right hand bank.
77 Rear Heated Oxygen Sensor Circuit.
82 Crankshaft Position Sensor.
84 A/T Diagnosis Communication Line.
85 VTC Solenoid Valve Circuit.
86 Fuel Injection System Function right hand bank.
87 Canister Control Solenoid Valve Circuit.
91 Front Heated Oxygen Sensor Heater Circuit right hand bank.
94 TCC Solenoid Valve.
95 Crankshaft Position Sensor.
98 Engine Coolant Temperature Sensor.
101 Front Heated Oxygen Sensor Heater Circuit right hand bank.
103 Park/Neutral Position Switch Circuit.
105 EGR and EGR Canister Control Solenoid Valve Circuit.
108 Canister Purge Control Valve Circuit
ECU Diagnostic Mode Procedures
Mode I - Exhaust Oxygen Sensor Monitor
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Use Mode I to determine if the Oxygen Sensor is functioning properly.
Warm the engine to normal temperature.
Run the engine above 2000 RPM under no load while looking at the ECU.
Make sure the GREEN LED goes on and off more than five times during ten seconds at 2000 RPM.
If the number of flashes are not more than five, replace the oxygen sensor. If the LED does not flash, check the sensor's circuit.
Mode II - Mixture Ratio Control Monitor
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Use Mode II to determine if the air/fuel mixture is cycling correctly.
Warm the engine to normal operating temperature.
Turn the dial on the ECU fully clockwise (or if you have a switch, turn it on).
After the LED flashes twice, turn the dial fully counter clockwise (or turn the switch off).
Run the engine above 2000 RPM under no load while looking at the ECU.
If the RED LED blinks simultaneously with the GREEN LED, the air/fuel mixture is cycling properly.
If the RED LED stays off, the mixture is more than 5% rich.
If the RED LED stays on, the mixture is more than 5% lean.
If the RED LED stays on or off above 2000 RPM, complete the diagnostics before beginning repairs.
Mode III - Stored Fault Code Reporting
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Use Mode III to retrive all stored trouble codes in memory.
Use the above posted procedures.
Mode IV - Switch Operation Monitor
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Use Mode IV to determine if the Throttle Position Sensor (TPS), Starter circuit and/or Vehicle Speed Sensor (VSS) are in proper working order.
Turn the ignition switch on, but do not start the engine.
Turn the dial on the ECU fully clockwise. After the LED flashes 4 times, turn the dial fully counter clockwise.
Make sure the RED LED is turned off.
Make sure the RED LED turns on when depressing the gas pedal. If not, check or replace the Throttle Position Sensor.
Make sure the RED LED turns on when turning the ignition key the START position. If not, check or replace the starter.
Drive the vehicle with the ECU unbolted and within view. Make sure the GREEN LED turns on when speed is 12 MPH or more. If not, check or replace the Vehicle Speed Sensor.
Mode V - Real Time Diagnostic Function
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Use Mode V to determine if the Crankshaft Position Sensor (CPS), Mass Air Flow Sensor (MAFS) and/or Ignition signal are working properly.
Start engine.
Turn the dial on the ECU fully clockwise.
After the LED flashes 5 times, turn the dial fully counter clockwise.
Make sure LEDs do not flash for 5 minutes when racing or idling the engine.
If it flashes, count the number of flashes, turn engine off, and see the following 3 paragraphs. Perform real-time diagnosis insepction and repair or replace malfunctioning part if present.
if LEDs do not flash for 5 minutes, turn engine off.
If the RED LED flashes 3 times for 1.5 seconds, check the Crankshaft Position Sensor. Check the harness continuity at CPS when the engine is stopped. Inspect the harness for dust and clean if necessary. Check the pin terminal at ECU for bends and remove them as necessary. Reconnect harness and recheck continuity. During real-time diagnosis, tap the harness connector or component and check if trouble code is displayed. If so, replace terminal.
If the GREEN LED flashes twice-3 times for 0.5 seconds, check Mass Air Flow Sensor. Check the harness continuity at MAFS when the engine is stopped. Inspect the harness for dust and clean if necessary. Check the pin terminal at ECU for bends and remove them as necessary. Reconnect harness and recheck continuity. During real-time diagnosis, tap the harness connector or component and check if trouble code is displayed. If so, replace terminal.
If the GREEN LED flashes 4 times for 0.2 seconds 3 times, check the ignition signal. Check the harness continuity when the engine is stopped. Inspect the harness for dust and clean if necessary. Check the pin terminal at ECU for bends and remove them as necessary. Reconnect harness and recheck continuity. During real-time diagnosis, tap the harness connector or component and check if trouble code is displayed. If so, replace terminal.
Hope this helps...
This is from 88offroad
According to the chilton manual 1970-88 ours don't work this way it is only off or on in mode 3. and we can not clear codes. disconnect battery ect.
We a REAL GOOD at following directions and did yours and did not work. but see the following codes:
24 chiltons shows no items for this code
31 E.C.M ???? High signal
33 Exhaust gas circuit
there is no adjustment screw on this ecm if there was we would adjusted it.
Do I need a carb and points and pitch the ecm to make this thing run????
If so where can I get one.
PLEASE excuse my sarcasm (getting a little frustrated) and thank you for you expertise
Linear Mode
