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 Ford Expert Your Own Question

Ford Expert
Ford Expert, Shop Foreman, Master Technician
Category: Ford
Satisfied Customers: 599
Experience:  Ford Master Certified in, Advanced Engine Performance, Advanced Electronics,
1759573
Type Your Ford Question Here...
Ford Expert is online now
A new question is answered every 9 seconds

93 mustang: trouble code 15 pcm rom fault..bucking..normal driving

Customer Question

I have a 93 mustang that is giving trouble code 15 pcm rom fault. with the key in off position. Its a new computer in the car but has been bucking very bad under normal driving. the car also has a chip. dont know if computer was bad or maybe chip
Submitted: 5 years ago.
Category: Ford
Expert:  Ford Expert replied 5 years ago.

did you take the chip out and drive it?

What mods?

Is the replacement computer new or used?

Customer: replied 5 years ago.
trick flow heads e cam trick flow intake,full legnth headers,410 gear.the car ran the same with chip out. It was a new A9L computer that I put in. I also changed the fuel pump to a 255lph. the problem is the car ran great until i put away last year. it ran consistent 12.30's at 111mph. then this year car went 12.99 102 to 103mph. after that the car would buck real bad at 2700 in third 4th and 5th gear. when driving normal. the chip was also set up to run without o2 sensors. alot of friends, and mechanics,but im ready to give up, pretty muchlost the whole seaon b/c of this problem
Expert:  Ford Expert replied 5 years ago.

If you are satisfied with the information I have provided "Please click "Accept". This does not close the session.

 

The small fee that is paid here (that you selected) is far less than a dealer would charge for diagnostics so please click accept. Thank you for using Just Answer.

 

Sounds like a fun ride.

 

Read all.

 

Code 15 indicates that the pcm has experienced a power interrupt in its KAM (Keep Alive Memory). You need to disconnect the pcm and test between pins 1 and 40 then pin 1 and 60, while grasping and wiggling the harness from the pcm to the dash ignition switch area. If you see a power fluctuation then repair the harness. You also need to be sure that NOWHERE is the eec harness close to any ignition component ie: coil, coil wire, secondary ignition wires etc. Some of the time I found no voltage to the KAM circuit and some of the time I replaced the pcm. So make sure to check the voltage. If both computers run the same with the chip out and voltage checks out ok, you may to look at a secondary problem. The bucking @ 2700rpm's indicates to me a secondary ignition breakdown. This is a typical scenario for ignition failure, high gear and low rpm's. This is exactly how I diagnosis ignition concerns today!, when road testing a car. You could have a concern with induction in the way the secondary ignition wires are routed. On the 15426378 firing order make sure #7 & 8 ignitioin wires are NOT paralell they must cross each other or be seperated from each other. Run another wire between them at the cap. More than once has someone brought a car in with buck and a miss with the plugs wires bundles together with a zip tie! A definite no-no. Remember code 15 could only be a loss of voltage to the pcm. Pin (1) should have voltage at all times, and pin(s) 40 & 60 are the ground side. Pin 1 is only the KAM circuit and a lot of guys disconnect the computer and/or battery when going the track to reset the fuel and ignition tables to get quicker et's anyway generatng a code 15. If the code is just a loss of voltage on pin 1 then I don't think this is your concern for running bad. If the voltage is good then I believe the pcm could be the cause of concern, because it indicates an internal problem with the pcm which may be affecting more than one circuit. Good luck Happy Thanksgiving. I will be here to answer any further concerns you may have. I race as well autocross, 02 GT 5spd bassini full exhaust crazy horse performance tune, sucks when it is not running right. This problem can be fixed just may take some time.

Ford Expert, Shop Foreman, Master Technician
Category: Ford
Satisfied Customers: 599
Experience: Ford Master Certified in, Advanced Engine Performance, Advanced Electronics,
Ford Expert and 3 other Ford Specialists are ready to help you
Customer: replied 5 years ago.
I appreciete all the info. just to add one thing.code 15 is reading with scanner on koeo. when we switch it to koer it says communication loss. also when i changed battery it seems like it would create a 15. happy thanksgiving and im very thankful for your help
Expert:  Ford Expert replied 5 years ago.

With the code in koeo the pinpoint test says to replace the pcm without doing any testing...

Thank you for the accept.

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:

 
 
 
  • AlvinC answered a question about my Ford truck that only someone with an in-depth knowledge of his subject would have known what was going on. Rich D USA
< Last | Next >
  • AlvinC answered a question about my Ford truck that only someone with an in-depth knowledge of his subject would have known what was going on. Rich D USA
  • Because of your expertise, you armed me with enough ammunition to win the battle with the dealer. They are installing a fuel filter and fuel pump at no charge to me. Molly USA
  • I needed help with my car on Saturday morning....got a response in 5 minutes, and it was the perfect solution. Thanks again to your service. Jason V. Kirkland, WA
  • I do know, after going though this with JustAnswer, that I can somewhat trust my mechanic but I will always contact you prior to going there. BR New Jersey
  • 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
 
 
 

Meet The Experts:

 
 
 
  • Ron

    ASE Certified Technician

    Satisfied Customers:

    20942
    23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
< Last | Next >
  • http://ww2.justanswer.com/uploads/FO/fordguy4u/2011-12-17_222940_HPIM1257.64x64.JPG Ron's Avatar

    Ron

    ASE Certified Technician

    Satisfied Customers:

    20942
    23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
  • http://ww2.justanswer.com/uploads/MU/muddyford/2012-6-13_1204_1.64x64.png Chris (aka- Moose)'s Avatar

    Chris (aka- Moose)

    Ford Technician

    Satisfied Customers:

    22382
    16 years experience with Ford.
  • http://ww2.justanswer.com/uploads/JM/jmcdo28/2012-2-23_01655_resized.64x64.jpg John Mc's Avatar

    John Mc

    Ford Technician

    Satisfied Customers:

    5493
    19 years Ford Lincoln Mercury experience
  • http://ww2.justanswer.com/uploads/wmarti7/2009-4-18_04332_Avatar.jpg Chuck's Avatar

    Chuck

    ASE Certified Technician

    Satisfied Customers:

    1684
    33 Years Experience,Ford Senior Master,ASE Master,L1 Advanced Engine Performance
  • http://ww2.justanswer.com/uploads/CR/crzydrvr00/2013-11-3_12123_246347.64x64.jpg Richard's Avatar

    Richard

    ASE Certified Technician

    Satisfied Customers:

    1518
    12 years at a Ford Lincoln/Mercury and Jaguar dealer as a technician and shop foreman.
  • http://ww2.justanswer.com/uploads/BA/baddad1/2014-4-1_23659_avatar.64x64.jpg Mike V.'s Avatar

    Mike V.

    Auto Service Technician

    Satisfied Customers:

    789
    25 years experience on all makes and models, Licensed NYS Inspector.
  • http://ww2.justanswer.com/uploads/lostrider/2009-9-26_23144_php4VNWAA_c1PM1.jpg lostrider's Avatar

    lostrider

    Ford Technician

    Satisfied Customers:

    2940
    ASE Master Technician, Ford Senior Master Technician,Diesel certified, ASE Master, 22 yrs FORD exp.