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Ecu Self-diagnostics For 87-95 Pathfinder


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#1 OFFLINE   88pathoffroad

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Posted 30 November 2003 - 08:43 PM

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 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 and the VG30E ECU has a slotted switch that turns 1/4 or 1/2 turn clockwise and counterclockwise to do the same task. Some early 4-cyl HB ECU's have the switch as well. In any case it will have one or the other.

Pictures: This is the ECU from my very dirty (and wrecked) 89 VG30i Pathfinder. VG30E ECU's have a slotted round switch in the same place as the toggle switch.

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.
0AB4C482-309A-47C6-A92C-79EF37F83851-435

 

Diagnostic selector switch with cover installed

65D47285-E8FC-453C-A9B1-B2D51DBB24DD-435
Diagnostic selector switch with switch cover removed and set on top of the ECU.
9B8622CF-69D7-404F-AE4C-11FC0C2BD167-435

This is where the LED lights are visible on top of the ECU.
wd21ecu3.jpg

For 4-cylinder:
1. Turn the ignition switch on, but do not start the engine. All of the lights in the dash should be on.
2. Turn the 'diagnostic mode selector' screw on the ECU fully clockwise. The check engine light will go out. Wait 5 seconds, then turn the screw fully counter clockwise.
3. The check engine light will then begin to flash the trouble code. (number of long flashes is the 1st digit, number of short flashes is the 2nd digit)
4. To clear all stored codes and turn the check engine light off, turn the screw fully clockwise while it is in diagnostic mode. Wait 5 seconds, then turn the screw fully counter clockwise.
5. To keep the codes stored, simply turn the key off as the check engine
light is flashing and the ECU will keep all stored codes and the check engine light will remain on.

For V6:
1. Turn the ignition switch on, but do not start the engine. All of the lights in the dash should be on.
2. For VG30i: 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.
For VG30E with slotted switch: Turn the 'diagnostic mode selector' screw on the ECU fully clockwise. The check engine light will go out. Wait 5 seconds, then turn the screw fully counter clockwise.
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.
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.

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
-----------------------------------------------------------------------
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
-----------------------------------------------------------------------
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
-----------------------------------------------------------------------
Use Mode III to retrive all stored trouble codes in memory.
Use the above posted procedures.


Mode IV - Switch Operation Monitor
-----------------------------------------------------------------------
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
-----------------------------------------------------------------------

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...


Edited by nunya, 20 December 2012 - 04:18 PM.
updated a couple pics to active ones


#2 OFFLINE   NitRo_BooGiE

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Posted 12 July 2004 - 12:10 AM

Hi there . I just bought my pathy a few months back and this forum is really helpful.
On your post up top i was wondering if the ECU is located in the passenger side kick panel?
Also can you guys please give me some tips on how to do a proper tune up on a 1993 pathy what kind of plug to use and so on.
Thanks
MiTrO

#3 OFFLINE   statikuz

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Posted 12 July 2004 - 08:34 AM

Search! ECU is under passenger seat. ;)

#4 OFFLINE   Hook88

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Posted 21 July 2004 - 06:17 AM

I don't know about the rest of you out there, but to get to the ECU under the seat and get that plastic cover off was quite a pain in the a! I tried using different tools to get that screw undone, but to no avail. Then :eek: , it dawned on me to take the seat out instead. Man did that make a difference!

All you have to do is unscrew the two front bolts and then take the plastic covers off the back of the chair rail that cover the back two bolts and unscrew them. Bing, the front seat is mobile and I just moved it toward the back seat.

Now the ECU is accessible, I can get that stupid plastic cover off and I can put the service manual on the drivers seat for easy reading while I lean in with the passenger door open. Also, it makes it easier to access the ignition to turn the key to the "on" position. Hope this might help others!

#5 OFFLINE   94extreme

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Posted 21 July 2004 - 06:54 AM

it depends on the years. the later ones (mine is 94) you just move the passenger seat forward and you can access the ECU without a prob. I think you only have to remove the seat on the first gen ones.

#6 OFFLINE   joeytattoo

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Posted 05 September 2004 - 09:57 AM

I'm cleaning my rig right now and have a question about my ecu .Well my seats are out of the front of the truck and I want to move the ecu can I put it in the glove compartment with out adding more wire.

#7 OFFLINE   94extreme

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Posted 06 September 2004 - 05:53 AM

you'll need a longer ground wire.

#8 OFFLINE   90seven

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Posted 19 January 2005 - 01:34 PM

Can you find the Self-Diagnostic procedures for the 3.3L Engines? 97 model.

#9 OFFLINE   88pathoffroad

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Posted 23 January 2005 - 03:12 AM

There are none AFAIK. OBDII engine systems need a scanner to retrieve error codes.

#10 OFFLINE   90seven

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Posted 23 January 2005 - 04:09 AM

So, you mean to tell me that the only way for me to check the truck is to pay $75 at the repair shop? :o :sniff: :sniff: :o

#11 OFFLINE   snosnk

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Posted 23 January 2005 - 11:13 AM

Hey 90seven,
Try checker auto parts. they'll do it for free. or at least they will here.

#12 OFFLINE   lewisnc100

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Posted 04 April 2005 - 04:47 AM

The 96-2000 year Pathfinders have a diagnostic mode selector screw on the ECU. The ECU is located directly above the gas pedal tucked up behind the dash, with the mode selector screw on the top. The steps for the 4-cylinder at the top of the thread are the exact steps for the 96-2000 pathfinders once you find and access that screw.

#13 OFFLINE   Trainman

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Posted 04 April 2005 - 08:08 AM

How about for 2001-2004, with the 3.5 L? Or are we out of luck and need to purchase a scan tool? :shrug: If so, any ideas on a reasonable scan tool for us not so mechanically inclined? I have the check engine light on, came on 36 km after fueling up, so everyone guesses it is the gas cap but no one here has a tool that will read the code. They want me to go to the dealer. Of course I have to go to the dealer for the gas cap anyway, that's the way it works in a small town! Thanks.

#14 OFFLINE   lewisnc100

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Posted 04 April 2005 - 10:34 AM

Sorry, you're out of luck with 2001+ years. I do have an Actron code reader that runs about $100, very easy. Harbor Freight sells a very simple reader for $39.95, not sure how well that one works. Or there's always Autozone, they'll read it for free for you (outside of CA).

#15 OFFLINE   Harbinger

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Posted 26 April 2005 - 07:36 PM

I tried searching for this, but to no avail.

I finally got around to checking my mode 3 codes, and all I was throwing is 44, ECCS Normal Operation. Does that mean don't worry be happy now? Or is it something else?

#16 OFFLINE   88pathoffroad

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Posted 27 April 2005 - 08:37 PM

The ECU usually won't give you error codes unless something emissions-related quits working. Running funny isn't really emissions related, even if it is annoying. Try a tune-up and thorough checking-over first.

#17 OFFLINE   Harbinger

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Posted 28 April 2005 - 12:52 PM

I might try the O2 sensor mode tonight, as I have theories thats gone bad (poor milege) also will try replacing my fuel filter and what not for the rough running.

What exactly does a code 44 mean?

#18 OFFLINE   WRL69

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Posted 18 October 2006 - 01:13 PM

There is any kind of plug to conect a scanner in my 93' Pathy SEV6 A/T (VG30E), or only is the ECU to diagnostic procedure?

In manual maintenance book there is a sketch referring to "Check Connector for ECCS Checker Box". I tried to connect a scanner there but it didn't read anything.

Regards,

#19 OFFLINE   88pathoffroad

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Posted 18 October 2006 - 01:16 PM

There is no data port on a 93, no. You have to use the procedure listed at the beginning of this thread to check your error codes.

#20 OFFLINE   89_trailboss

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Posted 21 October 2006 - 08:11 PM

are any of the LED's supposed to be on while driving? my red ones on all the time.




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