Resetting The Ecu On An 89 Pathy 3.0L

[krmiller07]

Does anyone have the proper method or at least a successful method of erasing the codes or resetting the ECU on the 3.0L Pathy? I have just replaced the O2 sensor on my truck with a Bosch factory replacement unit. I have read on here, that some people have simply disconnected the battery for as long as 12 hours. The local dealer says this isn't the proper method, and would be happy to reset it for $90.00 hr, 1 hour min ! He also said you need to change the 'head temp sensor' or coolant sensor as the work in unison at keeping the TBI working properly and keeping fuel mileage in line.

I had a posted on here about a week ago, in regards to the very poor fuel mileage I get both in town and on the Hi way. The motor is stock, with about 40k miles on it. The only changes are: K&N air filter, Warn Hubs and no Cat ( Bought it this way ). Aside from that, the engine runs very good and seems to make pretty good power, idles smooth with no backfires or 'popping' either stationary or decelerating. It even blows 'smoke rings' out the tail pipe idling !

 

Thanks for the suggestions in advance : ).

[jj big shoe]

The FSM for my 87 says:

Warm engine

turn diagnostic switch "on"

after lamps flash 3 times, turn switch "off"

read flashes

 

Here's the note I think you're interested in:

Caution - During displaying code # in self-diagnostic (mode 3) if another diagnostic mode should be done, make sure to write down the malfunctioning code # before turning diagnostic selector "on", or select the diagnostic mode after turning the ignition switch "off". Otherwise self-diagnostic information stored in the ECU memory will be lost.

 

The stored codes should clear once you turn the mode selector switch back to the "on" position w/o turning the ignition key off.

 

The FSM also says:

codes stored in Mode 3 diagnostics will automatically be cleared once the starter is activated 50 times. If the item which has beed judged to be malfunctioning and stored in memory is again judged to be malfunctioning before the starter is operated fifty times, the second result will replace the previous one. It will be stored until the starter is operated fifty times more.

 

Basically, the code will clear once you start your truck fifty times. If the code pops up again, it'll take another fifty times w/ no problem to clear.

 

Are you sure you have the right O2 sensor and is the lack of a CAT throwing off the emission system?

Edited March 13, 2010 by jj big shoe

[krmiller07]

The FSM for my 87 says:

Warm engine

turn diagnostic switch "on"

after lamps flash 3 times, turn switch "off"

read flashes

 

Here's the note I think you're interested in:

Caution - During displaying code # in self-diagnostic (mode 3) if another diagnostic mode should be done, make sure to write down the malfunctioning code # before turning diagnostic selector "on", or select the diagnostic mode after turning the ignition switch "off". Otherwise self-diagnostic information stored in the ECU memory will be lost.

 

The stored codes should clear once you turn the mode selector switch back to the "on" position w/o turning the ignition key off.

 

The FSM also says:

codes stored in Mode 3 diagnostics will automatically be cleared once the starter is activated 50 times. If the item which has beed judged to be malfunctioning and stored in memory is again judged to be malfunctioning before the starter is operated fifty times, the second result will replace the previous one. It will be stored until the starter is operated fifty times more.

 

Basically, the code will clear once you start your truck fifty times. If the code pops up again, it'll take another fifty times w/ no problem to clear.

 

Are you sure you have the right O2 sensor and is the lack of a CAT throwing off the emission system?

Thanks, Yes I have the correct O2 sensor, they come with 2 plugs attached to a 'pig tail' running up from the sensor. As far as the 'Cat', well the O2 sensor is upstream from the CAT by a fair amount. Someone else responded to a previous posting I put on here, regarding the very poor gas mileage I have been getting, they claimed that the O2 sensor really only functions during warm up, or until the engine or coolant reach a pre-determined tempature ( 160-170*F) then it goes from a 'closed loop' system, to an 'open loop' system. My uderstanding of this is, once the engines at operating temp, the O2 sensor reall doen't monitor the exhaust or send a signal to the ECU, calling for mixture changes or adjustments. Is this the case ?

I owned one of these trucks when they came out in 87. I bought one brand new, with an Automatic Trans, ans I don't remember the mileage being this bad. It wasn't great, but it avg. more than 8-10 MPG on the hiway.

I'm open to all ideas !

 

Thanks again,

 

krmiller07

[JamesRich]

Thanks, Yes I have the correct O2 sensor, they come with 2 plugs attached to a 'pig tail' running up from the sensor. As far as the 'Cat', well the O2 sensor is upstream from the CAT by a fair amount. Someone else responded to a previous posting I put on here, regarding the very poor gas mileage I have been getting, they claimed that the O2 sensor really only functions during warm up, or until the engine or coolant reach a pre-determined tempature ( 160-170*F) then it goes from a 'closed loop' system, to an 'open loop' system. My uderstanding of this is, once the engines at operating temp, the O2 sensor reall doen't monitor the exhaust or send a signal to the ECU, calling for mixture changes or adjustments. Is this the case ?

I owned one of these trucks when they came out in 87. I bought one brand new, with an Automatic Trans, ans I don't remember the mileage being this bad. It wasn't great, but it avg. more than 8-10 MPG on the hiway.

I'm open to all ideas !

 

Thanks again,

 

krmiller07

 

They have it backwards. The system runs in open loop with preset values until the motor reaches operating temp, then it goes into closed loop. In closed loop it monitors all the sensors to give you the correct fuel mixture. Everything must be in good order to function properly, even a loose or coroded ground could cause problems.

I wish these trucks would be like the newer OBDII system that can give you live data. That way you could look at the sensor values to see if they are working properly. The only way to check these sensors is to back probe them but you must know what values they are supost to run at.

First you must make sure your ignition system is in good shape then go to the emission system. With the limited data the computer gives us to trouble shoot I really wish someone made a replacement intake and carburetor setup.

James

[krmiller07]

They have it backwards. The system runs in open loop with preset values until the motor reaches operating temp, then it goes into closed loop. In closed loop it monitors all the sensors to give you the correct fuel mixture. Everything must be in good order to function properly, even a loose or coroded ground could cause problems.

I wish these trucks would be like the newer OBDII system that can give you live data. That way you could look at the sensor values to see if they are working properly. The only way to check these sensors is to back probe them but you must know what values they are supost to run at.

First you must make sure your ignition system is in good shape then go to the emission system. With the limited data the computer gives us to trouble shoot I really wish someone made a replacement intake and carburetor setup.

James

 

Thanks James,

 

Actually I did find a company that will and can modify the stock intake to accept a small 2 barrel carb. Apperently these are very popular with the people that race the older Datsun 510's with a V-6 upgrade. The only problem I understand, is you also have to change the distributor and McGyver a way to properly hook up your throttle cable. I have no idea how comlicated it could get with all the other wiring thats part of the TBI ? There are some posts on a site dedicated to the VG-30.

I'll dig around and see if I can provide the links or sites. I think this is on of them : http://vgpowered.informe.com/index.php

[krmiller07]

They have it backwards. The system runs in open loop with preset values until the motor reaches operating temp, then it goes into closed loop. In closed loop it monitors all the sensors to give you the correct fuel mixture. Everything must be in good order to function properly, even a loose or coroded ground could cause problems.

I wish these trucks would be like the newer OBDII system that can give you live data. That way you could look at the sensor values to see if they are working properly. The only way to check these sensors is to back probe them but you must know what values they are supost to run at.

First you must make sure your ignition system is in good shape then go to the emission system. With the limited data the computer gives us to trouble shoot I really wish someone made a replacement intake and carburetor setup.

James

 

Here is the email and info he sent me. I wish I knew about this option last year, I had to scare up a used Throttle Body from a salvage yard in Arkansas so I could rob the injectors from it.Used cost me $400.00, but New from Nissan was over $700.00. Just for the injectors !

 

Hi Keith. Thanks for the questions and sorry it has taken so long to get back to you.

 

We are able to modify the TBI equipped VG30 intake manifolds to accept a 350 or 500cfm Holley 2bbl.

 

http://datsun510.com/photopost/showphoto.php?photo=10226

 

That’s the easy part. The challenge right now is the ignition because the VG30 distributor with vacuum advance for carbed applications is currently NLA from Nissan…

 

 

 

What I heard long ago was that The NLA Nismo/Saudi truck distributor is apparently available again through Nissan Motorsports.

 

1-866-754-5500 p/n M-22100-V6402 14-21 day delivery - $292.10 USA - ask for Russell internet sales.

 

But I have yet to have anyone confirm that they were indeed able to get one.

 

www.nissanparts.cc lists them as well.

 

 

 

In lieu of the cool distributor, others have made their own ignition systems:

 

Option 1) I have is reports of at least one customer taking the guts out of a 240/260/280z car distributor and somehow grafting them into the VG30 distributor.

 

Option 2) recommended by Dave (the guy who builds the VG30 install kits) is to use an Electromotive DFI system.

 

Option 3) some short track racing series called “pro-6” used the stock Z31 distributor with a Crane Hi-6 ignition box.

 

Option 4) a guy named Mike Guido (with a VG30 powered mini) mounted a magnetic pickup through the side of the stock distributor and has an MSD digital 6 control for it.

 

Option 5) mega-spark (look up mega-squirt on google)

 

 

 

There are probably other options as well, but that is what I have for you.

 

 

 

--carter

[JamesRich]

I hadn't thought that far ahead yet, the ignition would be a problem. I remember seeing after market duel carb intakes for the older pickups with a four cylinder but they already had a carb so the distributor would not have to be changed.

James