How JustAnswer Works:

  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.

Ask Roy F. Your Own Question

Roy F.
Roy F., A.S.E. Certified Master Technician
Category: Nissan
Satisfied Customers: 132
Experience:  General Motors World Class Certified, A.S.E. Master Certified, 23 yrs. Exp. in the auto repair field
16401892
Type Your Nissan Question Here...
Roy F. is online now
A new question is answered every 9 seconds

88 Nissan Pathfinder 4x4: injector..circuit..vehicle was running fine

Resolved Question:

I have an 88 Nissan Pathfinder 4x4 XE with the 3.0 engine. I am getting an error code 51 (open injector circuit).   the vehicle was running fine when i took it shopping, upon leaving the store the vehicle started sputtering and won't go iver 2750RPM. I found it had gone to failsafe. In neutral the vehicle would rev all the way to redline but in gear would not go over 2750. A few days later the vehicle wouldn't go over 2750 even in neutral. I had the injectors tested by a local injector shop and they are good. I have tested all the injector wires from the injectors to the computer and they are showing continuity. I have already replaced the mass air sensor. I get the same problem with it connected and disconnected (resetting the computer every time). The vehicle has 150k miles on it and I think the problem occured before it has new injectors, remanned mass air sensor, o2 sensor, and hoses. I do not hear any vacuum leaks and have been unable to find any. Help me please!
Submitted: 5 years ago.
Category: Nissan
Expert:  Roy F. replied 5 years ago.
HelloCustomer
Can you tell me if you have checked continuity from the ECM (computer) harness to the injectors? then comfirm harness connection pin tension at the ECM connector. you have to have a good connection for the ECM to perform properly.
Customer: replied 5 years ago.
to check continuity I had disconnected the wires from the computer and the injectors from the harness and used the tester between those two points. Not sure how to do:harness connection pin tension at the ECM connector. I have made sure the connector is seated fully and pushed each individual wire into the connector.
Customer: replied 5 years ago.
I forgot to mention that while I was having this issue the water pump had started to leak. That has been replaced and I replaced the timing belt as well (it appeared to have been one tooth off in the cam) it's timing has been set so that is not an issue. oh and the ecu has been replaced as well.
Expert:  Roy F. replied 5 years ago.
lol ok that rules that out yoU are still getting the code with the new ecm?
is it possible you shorted the circuit when repairing the timing belt? damaging the new ecm?
Customer: replied 5 years ago.
yes with both ecm's, this morning I reset it and verified that codes were clear (code 55) and started the vehicle. before i was able to rev the engine up to 3000 it had shifted back to failsafe and refused to go past 2750.
Expert:  Roy F. replied 5 years ago.
thats funny i just realised it is code 55 that means there is no trouble found in the self diagnostic circuits. per alldata

Code 55 indicates no malfunction in the self-diagnostic circuits.
Customer: replied 5 years ago.
but then it jumps to failsafe and won't go over 2750 and shows a code 51.
Expert:  Roy F. replied 5 years ago.
oh ok ya you need to confirm all resistance in the harness to the injectors. mabe an injector is faulting when it warms up. all the diagnostic charts lead back to that.
Thank You,
Roy
Customer: replied 5 years ago.
best way to do this would be? i have an ohmmeter but my leads are not long enough, i can patch a couple wires to it to get the length, but do i attach to black or white and for which injector? My understanding is the black is common to the two injectors,
Expert:  Roy F. replied 5 years ago.
Try this, go to the ecm and unplug the connector and check continuity through the harness to the injectors with out unplugging the injectors. That would check the whole circuit.

Thank You,
Roy
Customer: replied 5 years ago.
i was incorrect before, the white are tied together in the engine bay (factory crimp). at the ecm i am getting around 1.2 between the white and black for both blacks. I am starting to wonder if it is the safety relay in the passenger kick panel but haven't been able to find any information on that one or what it will do.
Expert:  Roy F. replied 5 years ago.
does the engine run ok with codes cleared and not reving it up?
the jiffy injector clean doesnt test electricly. it may have an injector failing under high load.
Customer: replied 5 years ago.
yes the engine idles fine, but if we rev at all (even once) the computer goes to failsafe, i have had the aircleaner off all afternoon and when i went to check the continuity i could still smell gas from the throttle body, I thought that might be because of failsafe running so rich.
Expert:  Roy F. replied 5 years ago.
is the fuel cut solenoid what you are refering to as the fail safe?
it is used to prevent dieseling in some models.

a. Check the operation of injector "A" by disconnecting the red wire from the throttle body harness connector (at the location shown ) to disable injector "P"

b. Start the engine and allow to idle. With injector "B" disabled, the engine should run at idle on injector "A" in the fail safe mode. If idle is satisfactory, injector "A" is good. Turn off the engine, reconnect the red wire disconnected in Step 2a and proceed to Step 2c. If the engine will not idle, or idles poorly, injector "A" is faulty and should be replaced.

c. Check the operation of injector "B" by disconnecting the green wire from the throttle body harness connector (at the location shown above) to disable injector "A".

d. Start the engine and allow to idle. With injector "A" disabled, the engine should run at idle on injector "B" in the fail safe mode. If idle is satisfactory, injector "B" is good. Turn off the engine, reconnect the green wire disconnected in Step 2c and proceed to Step 3. If the engine will not idle, or idles poorly, injector "B" is faulty and should be replaced.
Expert:  Roy F. replied 5 years ago.
I hope that helps.
Thank You,
Roy

Customer: replied 5 years ago.
sorry it took so long to get back to you,
I put a new distributor cap on because the old one was pretty worn. No change (long shot but needed to be done)
I ran the test you have and both injectors idled great and even were able to rev to 2500 with no trouble (not willing to push them any further) when they were the only injector hooked up. I did redo all four of the connectors to make sure they were tight and making good contact.
the final thing i did was cleared the computer and ran it with both injectors hooked up (since redid all of the connections) but alas still got the same code and problem.

Next...?
Expert:  Roy F. replied 5 years ago.
HelloCustomer
It is difficult to have a solid answer with inconclusive tests. if everything is testing ok. I still suspect an injector being a fault. what is the OHM reading of the injectors?
Customer: replied 5 years ago.
at the ecm i am getting 1.7 and 1.7
Expert:  Roy F. replied 5 years ago.
HelloCustomer
Ok try this,clear the code. I know it can be irritating. disconnect one of the injectors and try to run the engine and see if it still wont go past 2700rpm then the other one. everything im looking at says the injectors should be 2.5 to 3.5 ohms. 1.7 can load the ECM down with too much AMP draw so it goes into failsafe(limp in mode). This one sounds like I would have fun finding the problem in person. I love a challenge.
Thank You,
Roy
Customer: replied 5 years ago.
nope both times when on one injector was in safe mode.

I have been messing with this for 3 months now and now am in need of this vehicle so of course it an urgency. Which direction should i start to kick it to get it to you? :)
Expert:  Roy F. replied 5 years ago.
Your funny, The best I can say is try new injectors I would Ohm them out at the parts store before installing.
Thank You,
Roy
Expert:  Roy F. replied 5 years ago.
I live in oregon. LOL
Expert:  Roy F. replied 5 years ago.
HelloCustomer
You know what some one else here brought a good point to my attention try disconnecting the MAF sensor and running the engine after clearing the codes. it may be a faulty mass air flow sensor.
Customer: replied 5 years ago.
heh, not the MAF again. On the original MAF that I had if i clear the codes and disconnect the MAF the vehicle won't start. If i connect it, it starts and runs in failsafe. once i had it started and in failsafe i can restart the vehicle with the MAF disconnected with no change. on my replacement MAF the same thing happens :) The first place i took it to check my injectors (who said they are running good) said it was my MAF which is why i got the replacement. It has taken me 2 months just to find the correct one.

Expert:  Roy F. replied 5 years ago.
HelloCustomer
WOW one time I encountered a similar problem You Had the maf off Rite. then try checking if its on upside down. you may laugh but ive seen it happen. its worth a try.
Customer: replied 5 years ago.
Well,

This particular one has a single keyway on one side and a double on the other, connector is impossible to install incorrectly. The MAF goes into the throttle body and has 3 screws, impossible to install that incorrectly and get the holes to line up...
Expert:  Roy F. replied 5 years ago.
HelloCustomer
well if the mass airflow sensor cant be fliped over I'll stick to the injectors being too low resistance causing high current (amp) draw. this will shut down the Ecm.
Customer: replied 5 years ago.
I will try to find someone that has some injectors for this vehicle tomorrow since everybody that might is closed here for the day
Expert:  Roy F. replied 5 years ago.
HelloCustomer
Ok thank you for your patience. This is a more than dificult problem to solve. Like I said before this would be tough to diagnose in person. Thank You again for using Just Answer.

Thank You,
Roy
Customer: replied 5 years ago.
Hello Roy,
I checked all the local stores and no one has new injectors for this vehicle, however my neighbor has a running 89 (same engine) and the salvage yard in this area had a running 89 (same engine as well), neither in failsafe mode. All of the injectors showed the same resistance on my multimeter. Started at 2.8 and ran down to 1.6-1.7. All the same thing my current injectors are doing. I called 3 dealerships and they couldn't give me any resistance information at all, they all said that they don't have the manual but i can bring it in to them and that they would need to order injectors.

Expert:  Roy F. replied 5 years ago.
Ok so yours are 2.8 then? or 1.7? 1.7is low maybe you can take a look at your neighbors maf sensor to confirm its location. it is possible to flip upside down i know it sounds silly, but it is possible. can you access a complete throttle body from a functional vehicle with injectors and maf sensor. some thing just isn't rite in the injector area. 2.8 ohms is good for injectors, 1.7 is not good.

Thank you,
Roy
Customer: replied 5 years ago.
when they first register they are around 2.8 and then they trickle down to 1.7. I switched MAF's with that vehicle and it worked in his and didn't change mine. His injectors are giving the same numbers as mine. Is there some other relay or fuse for the injectorss that could be causing this? I have found both for fuel system but nothing for efi or injectors. I have no way to get ahold of new injectors to test brand new but functioning pathfinders are showing the same numbers.

when i attach my probes i get an initial reading of 2.8 then 2.3 then1.9 then 1.8, then 1.7 all without moving the probes. I get the same thing on all the pathfinders.

My thoughts are that i have a vacuum leak somewhere in the system, but am not sure how to test them and which ones to try.
Expert:  Roy F. replied 5 years ago.
To check for a vacuum leak use a small propane source with a small vacuum hose attached to it. The vacuum hose needs to be aprox 1 foot long. Thats the tool you need . Now take the vacuum hose as the engine is idling. Run the hose around the manifold and throttle body. of course you need to have the propane on while doing this. you will here the engine speed increase an the event you have a vacuum leak. a good way to know what it will sound like is to put the vacuum hose into the throttle body as its running. and the engine will react (speed up or slow down).
I hope this was helpful
Thanks Roy
Customer: replied 5 years ago.
I had also heard of using carb cleaner, since i have a couple cans of that around... Will that work as well?
Expert:  Roy F. replied 5 years ago.
yes it has more hazzard of fire if it puddles up it can be dangerous.
Expert:  replied 5 years ago.
Ive been doing some research and only found three fixes for the dtc 51 and complaint you are having. Injectors, ECM, or MAF Sensor.

I hope this helps.
Thank You,
Roy
Roy F., A.S.E. Certified Master Technician
Category: Nissan
Satisfied Customers: 132
Experience: General Motors World Class Certified, A.S.E. Master Certified, 23 yrs. Exp. in the auto repair field
Roy F. and 11 other Nissan Specialists are ready to help you
Customer: replied 5 years ago.
Morning Roy,

Sorry about the delay in getting back to you thought i might be able to get my pickup fixed instead while i saved for injectors. I talked with a couple other mechanics and got some more information:

First here is a link that shows that the injectors should only be 1.5 http://www.asashop.org/autoinc/oct99/techtips.htm.

Second the othe rmechanics that i talked with thought maybe an injector fried open and was dumping fuel instead of pulsing. Would explain why would get good resistance but still going to failsafe mode (wouldn't ground).

But since we knew that the problems were one of 3 injectors, MAF, or computer. I went to the junk yard and got the entire throttle body from the 89 pathfinder (same engine). Swapped throttle bodies and now it works great. Just gotta put her through emmissions.

Went ahead and accepted answer thank you for all your time and effort on this but thought you might like the information for future customers.

Thanks Again
Chris

JustAnswer in the News:

 
 
 
Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.
 
 
 

What Customers are Saying:

 
 
 
  • I was in trouble with an electrical issue with my brand new Nissan. I frantically went online trying to find help and luckily I found your site. I reached a NISSAN tech named RIP. He was absolutely tremendous and helped me work through the issue. What a pro! cjaz Lexington, KY
< Last | Next >
  • I was in trouble with an electrical issue with my brand new Nissan. I frantically went online trying to find help and luckily I found your site. I reached a NISSAN tech named RIP. He was absolutely tremendous and helped me work through the issue. What a pro! cjaz Lexington, KY
  • I would (and have) recommend your site to others I was quite satisfied with the quality of the information received, the professional with whom I interacted, and the quick response time. Thanks, and be sure that I'll be back whenever I need a question answered in a hurry. Stephanie P Elm City, NC
  • used your service this weekend with "Trecers" help. thank you ,thank you, thank you. replaced an A/C fan motor. Local Auto Zone had part. $15.00 "tracer" fee and $40.00 for parts, I saved several hundreds of dollers at a shop. i will recommend you and use you in the future. David L. Richmond, TX
  • 9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much. Phil Marysville, CA
  • Lurch. Thank you very much. I had real doubts about this website but your promptness of response, quick followup and to the point answer with picture was incredible. Charles Walnut Creek, CA
  • As a single woman, I really appreciate an excellent and affordable opinion.
    Thank you Geordie, I will not hesitate to contact justanswer in the future!
    Sue Charleston, WV
  • Another great insight to what may be the problem. I will have my mechanic take a look at it tomorrow. Thanks again, Frank...you do indeed know your stuff. Jim Castleberry, FL
 
 
 

Meet The Experts:

 
 
 
  • Tim Mohr

    ASE MASTER TECH

    Satisfied Customers:

    446
    30 YRS EXPERIENCE, FOREIGN AND DOMESTIC, GAS AND DEISEL
< Last | Next >
  • http://ww2.justanswer.com/uploads/tsmodie/2009-6-10_144056_tim.jpg Tim Mohr's Avatar

    Tim Mohr

    ASE MASTER TECH

    Satisfied Customers:

    446
    30 YRS EXPERIENCE, FOREIGN AND DOMESTIC, GAS AND DEISEL
  • http://ww2.justanswer.com/uploads/CA/caprio23/2011-12-13_155550_20111213105344.64x64.jpg Anthony's Avatar

    Anthony

    ASE Certified Technician

    Satisfied Customers:

    306
    ASE Master Automobile Technician with over 18 years exp. in this field.
  • http://ww2.justanswer.com/uploads/FO/fordguy4u/2011-12-17_222940_HPIM1257.64x64.JPG Ron's Avatar

    Ron

    ASE Certified Technician

    Satisfied Customers:

    171
    34 years of automotive Repair
  • http://ww2.justanswer.com/uploads/MU/muddyford/2012-6-13_1204_1.64x64.png Chris(aka-Moose)'s Avatar

    Chris(aka-Moose)

    Nissan Technician

    Satisfied Customers:

    165
    16 years of experience
  • http://ww2.justanswer.com/uploads/EU/eurotec/2012-6-11_13153_mpjaphoto.64x64.JPG Marty's Avatar

    Marty

    ASE Certified Technician

    Satisfied Customers:

    127
    ASE & Bosch master tech. 30 years experience.
  • http://ww2.justanswer.com/uploads/BA/baddad1/2013-8-30_131413_11848761610058140852271553042976n.64x64.jpg Mike V.'s Avatar

    Mike V.

    Nissan Technician

    Satisfied Customers:

    7443
    Nissan factory trained and Certified Subaru Technician.
  • http://ww2.justanswer.com/uploads/CR/crzydrvr00/2013-11-3_12123_246347.64x64.jpg Richard's Avatar

    Richard

    ASE Certified Technician

    Satisfied Customers:

    92
    Nissan Tech ASE certified technician