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 BigBob Your Own Question

BigBob
BigBob, Shop manager/technician
Category: Chevy
Satisfied Customers: 4836
Experience:  Shop Manager with 25 years experience
Type Your Chevy Question Here...
BigBob is online now
A new question is answered every 9 seconds

1998 chevy tahoe: intermittent starting problem..tune..fires..bucks

Resolved Question:

Hi i have a 1998 chevy tahoe with a 350 it has a intermittent starting problem just had a fresh tune-up but still happens now and again I can here the fuel pump working and the truck will turn over but will faulter,i'll pump it a few times it attempts to start to no avail.
I'll keep on trying it about ten min. then it fires up been doin this for 3 years. Big bucks for fuel pump can't afford a a new one HELP ROB
Submitted: 3 years ago.
Category: Chevy
Expert:  BigBob replied 3 years ago.
Chat Conversation Started
Bob :

Greetings,

Bob :

Have you checked the fuel pressure with a guage?

Customer :

no

Customer :

thought fuel pressure leads tu fuel pump probs?

Bob :

That will be the first thing you need to do. You can at least check the fuel pressure regulator and make sure there is no fuel in the hose. Verify that fuel pressure, while cranking in the mode of hard start, is 60+ PSI You will need to eliminate this first.



VEHICLE THEFT DETERRENT (VTD) DESCRIPTION AND OPERATION

The vehicle theft deterrent (VTD) system functions are provided by the theft deterrent control module. The VTD system prevents vehicle operation if a valid (learned) transponder PASS-Key®III (PK3) ignition key is not used to start the vehicle. The theft deterrent control module has an exciter that is part of the theft deterrent control module as an assembly. The PK3 key has a transponder embedded in the plastic head of the key. The exciter is an antenna which is made up of wire coils which surround the ignition lock cylinder. The PCM enables the engines starter and fuel delivery system when it receives a valid (learned) password XXXXX the theft deterrent control module via the class 2 serial data circuit. The components of the VTD system are as follows:



  • Theft deterrent control module

  • Powertrain control module (PCM)

  • Ignition key (Transponder)

  • Ignition lock cylinder

  • Security indicator


THEFT DETERRENT CONTROL MODULE
Vehicles with steering column mounted ignition switches have the exciter integral with the theft deterrent control module which is located within the steering column. Vehicles with instrument panel mounted ignition switches have exciter modules separate from the theft deterrent control module with the vehicle wiring harness connecting the two. The theft deterrent control module for vehicles with instrument panel mounted ignition switches is located within the instrument panel. The theft deterrent control module can learn up to ten keys (transponder values).

The theft deterrent control module uses the following inputs, battery voltage, ignition switched voltage and ground circuit. The theft deterrent control module uses the following outputs, password XXXXX with the powertrain control module (PCM) via class 2 serial data circuit.

When an ignition key is inserted into the ignition lock cylinder, the transponder embedded in the head of the key is energized by the exciter coils surrounding the ignition lock cylinder. The energized transponder transmits a signal that contains its value, which is received by the theft deterrent control module. The theft deterrent control module then compares this value to a value stored in memory and performs one of the following functions:



  • If the transponder value is correct, the theft deterrent control module sends a class 2 message containing the modules enable password XXXXX the PCM.

  • If the transponder value is incorrect, the theft deterrent control module sends a class 2 message containing a disable password XXXXX the PCM.

  • If the theft deterrent control module is unable to measure the ignition key transponder value for one second, due to a damaged or missing pellet or a damaged exciter, it sends a class 2 message containing a disable password XXXXX the PCM.


IMPORTANT: If the PCM is unable to communicate with the theft deterrent control module (loss of class 2 state of health) after the vehicle has started, the module will consider itself malfunctioning and enter a fail enable state and illuminate the Security Indicator. The vehicle will not stall or stop running. If the PCM is in a fail enable state when the ignition is turned to OFF, it will remain fail enabled until the next time the vehicle is started. If the PCM is fail enabled the theft deterrent system is NOT active and the vehicle will start. The PCM will remain fail enabled until class 2 communication with the theft deterrent control module is restored.

POWERTRAIN CONTROL MODULE (PCM)
The powertrain control module (PCM) verifies that the password XXXXX from the theft deterrent control module via the class 2 serial data circuit is correct. The PCM can learn only one enable password. If the enable password XXXXX XXXXX the PCM enables the starter and fuel delivery systems.

The PCM disables the starter and fuel delivery systems if any of the following conditions occur:



  • The enable password XXXXX XXXXX

  • The system disable password XXXXX XXXXX by the theft deterrent control module.

  • No passwords are received - there is no communication with the theft deterrent control module.


THE IGNITION KEY (TRANSPONDER)
The ignition key for theft deterrent equipped vehicles is a typical looking ignition key with a transponder located in the plastic end of the key. The transponder value is fixed and unable to be changed. The theft deterrent system uses the ignition key transponder value to determine if a valid ignition key is being used to start the vehicle. There are approximately three trillion possible transponder values. There are no visible electrical contacts. The keys may be identified by the letters 'PK3' stamped into the steel shank of the key. The theft deterrent systems use the following types of ignition keys:














Master Keys

Master keys have a black plastic end for full access operation of the vehicle. Master keys may perform the following functions:


  • Start the vehicle.

  • Lock/unlock all of the door locks.

  • Lock/unlock all of the storage compartments.










Valet Keys

IMPORTANT: Valet keys have a gray plastic end which are NOT original equipment on this vehicle. Valet Keys are available on other GM vehicle lines.

Valet keys provide limited access to the vehicle and vehicle functions. Valet keys may perform the following functions:



  • Start the vehicle.

  • Lock/unlock all of the door locks.


IGNITION LOCK CYLINDER
The ignition lock cylinder performs all of the functions of a lock cylinder on a non theft deterrent equipped vehicle. The ignition lock cylinder for vehicles with theft deterrent may be located on the steering column or on the instrument panel. In either location the exciter coils surround the ignition lock cylinder such that they are very close to the head of the key which contains the transponder pellet.

If an ignition lock cylinder is replaced, new transponder keys must be cut to match the mechanical coding of the new lock cylinder. The new keys must be learned by the theft deterrent controller module. When replacing an ignition lock cylinder, refer to Programming Theft Deterrent System Components.

SECURITY INDICATOR OPERATION
The instrument panel cluster (IPC) illuminates the SECURITY indicator in the message center as determined by the vehicle theft deterrent (VTD) system. The IPC receives a class 2 message from the theft deterrent control module requesting illumination. The theft deterrent control module can command the IPC to illuminate the SECURITY indicator only when the ignition key is in the ON position. The security indicator is a malfunction indicator and does not illuminate during the bulb check when the ignition is turned to ON. If the PCM loses communication with the theft deterrent control module, the instrument cluster will also detect the loss of communication and will illuminate the SECURITY indicator. The SECURITY indicator can indicate both malfunctions (Indicator on steady) and tamper (Indicator flashing - indicating unauthorized operation). Under the following conditions the SECURITY indicator may be commanded to illuminate.






































SECURITY Indicator Stays Illuminated and Engine Starts

If the theft deterrent control module was unable to measure the ignition key transponder value or the powertrain control module (PCM) lost communication with the theft deterrent control module while the engine was last running, the indicator will remain illuminated during subsequent ignition cycles. This is to remind the driver that the vehicle theft deterrent system will not be functioning until the problem is corrected. The vehicle is fail enabled and will start.

SECURITY Indicator Illuminates when Engine is Running

If the theft deterrent control module is unable to measure the ignition key transponder value or the PCM loses communication with the theft deterrent control module while the engine is running, the indicator will be illuminated. If the key is turned to OFF, the vehicle will be fail enabled and will start if the condition still exists at the next attempt to start the vehicle will remain fail enable.

SECURITY Indicator Illuminated and Engine Does Not Start

The theft deterrent control module or the PCM has detected a problem with the theft deterrent system. The theft deterrent control module is unable to measure the ignition key transponder value. The System is in Learn Mode, refer to Programming Theft Deterrent System Components.

SECURITY Indicator Flashes and Engine Does Not Start

The theft deterrent control module has measured an incorrect transponder value when the ignition key is turned to the ON position. The transponder has not been learned by the theft deterrent control module. This is considered a tamper condition by the theft deterrent control module

Bob :

We need to determine if it is spark or fuel, so if these pressures are ok then we can look into the electrical ignition system. This also could be a plugged fuel filter.

Customer :

wow!! now that you totaled confused me! I know the security light has been on lately. as far as changingthe fuel filter it looks like the whole line has to be changed does a 1998 have a chip in the key head?

Bob :

The security light makes a world of difference, this may be your issue. When the car does not start does it just crank and not start or no crank at all?

Customer :

just cranks

Customer :

no start

Customer :

then after ten min it will start

Bob :

Ten min of leaving the key turned on or just come back in ten min and it works?

Customer :

attempt to start wait a a few min try again try again pump it then try it again until it starts

Customer :

turn on then turn off in between

Customer :

i also have left it and come back and it started goofy darn truck

Bob :

This could be a security issue. If the light is on then it is probably an ignition lock cylinder issue, this is where the pass key sensor is. Since the light is on this needs to addressed first. You will need to have the body control module scanned and see what the code is, this will tell us alot.

Customer :

ok then what

Bob :

The code will tell us which way to go. Whoever scans it has to be able to scan the body control module to get those codes. I think your ignition lock cylinder is bad, after replacing it you will have to do a key relearn. Most auto part stores will scan the computers for free, except in California.

Customer :

you mean if i go to napa they'll do all this ? i'm confused

Bob :

If they do free scans. Al you need to do first it get it scanned and see what the codes are. As long as you don;t live in California, Autozone or Advanced Auto will do it for free I know, but they have to scan the body control module, this is where the code will be. That will tell you which way to go. Get it scanned before anything else.

Customer :

k bob then what do we do

Bob :

After you get the code just right back through this thread and we can go further. Just respond here.

Bob :

If I am not online I will get back to you ASAP

Customer :

ok this may sound like a stupid question but how do i save this and get back in touch with you i'm just an ole nam vet just gettin by

Bob :

Thanks for serving!!!!!!! I appreciate all you have done for the country!!!!!! I will switch this over to a regular question and answer then you can just respond to it.

Expert:  BigBob replied 3 years ago.
Chat Conversation Ended

If you are still working with your Expert on this question, you can post additional replies and receive additional information on this page.  If you received a satisfactory answer in Chat, you can accept the chat conversation above.
Expert:  BigBob replied 3 years ago.
Just respond here when you get it. I also forgot to move this to the Chevy questions so I will do that right away.


Bob
Customer: replied 3 years ago.

Hi Bob I did'nt get a chance to get to auto zone had appts. at va all day but did notice when truck did not start security light was flashing when i let sit for 10 min. and just turned the ignition on light was not flashing and truck started right up!

So it has to be the ignition lock cylinder.

How esential is getting the codes opposed to just getting the repair done and how many dollars is this going to cost me (I hate to ask) Rob

Expert:  BigBob replied 3 years ago.
Yeah it does sound like the passlock sensor in the lock cylinder housing. Let me get some prices I will be back shortly.


Bob
Customer: replied 3 years ago.
k thanks
Expert:  BigBob replied 3 years ago.
Labor is about $160
part is about $40

I would still try to get the codes to be sure, because sometimes the passlock module is a problem and the housing.


Bob

Edited by Bob on 8/27/2010 at 4:24 AM EST
Customer: replied 3 years ago.
k bob Is this quote at a dealreship
Expert:  BigBob replied 3 years ago.
Yes, but the housing would cost more, and most independent garages could also do it.


Bob
Customer: replied 3 years ago.

k bob I think this solves my problem I guess I'll find out thanks for the expert advice and keep up the good work rob

Expert:  BigBob replied 3 years ago.
No problem!!!! Let me known if I can help further. Good luck and God Bless!!!





Bob



PS: don't forget to hit the green accept button if I have answered your questions. Even if you left a deposit I do not get credit until you do. Cool

Edited by Bob on 8/27/2010 at 4:47 AM EST
BigBob, Shop manager/technician
Category: Chevy
Satisfied Customers: 4836
Experience: Shop Manager with 25 years experience
BigBob and 3 other Chevy Specialists are ready to help you

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 having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money. Todd L Rochester NY
< Last | Next >
  • I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money. Todd L Rochester NY
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex Los Angeles, CA
  • Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult. GP Hesperia, CA
  • I couldn't be more satisfied! This is the site I will always come to when I need a second opinion. Justin Kernersville, NC
  • Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around. Esther Woodstock, NY
  • Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know. Robin Elkton, Maryland
 
 
 

Meet The Experts:

 
 
 
  • Tim's Auto Repair

    mechanic

    Satisfied Customers:

    7641
    Have owned a repair shop for 25 yrs.
< Last | Next >
  • http://ww2.justanswer.com/uploads/TI/tim37857/2011-10-28_23053_S6301814.64x64.JPG Tim's Auto Repair's Avatar

    Tim's Auto Repair

    mechanic

    Satisfied Customers:

    7641
    Have owned a repair shop for 25 yrs.
  • http://ww2.justanswer.com/uploads/DT/dt69nova/2012-6-15_234154_pic1.64x64.jpg Dave Nova's Avatar

    Dave Nova

    Chevrolet Technician

    Satisfied Customers:

    6870
    ASE Master Certification. GM World Class Certification
  • http://ww2.justanswer.com/uploads/ggrote1/2009-06-27_031011_me.jpg Gary's Avatar

    Gary

    Chevy Technician

    Satisfied Customers:

    5404
    15 years GM master tech
  • http://ww2.justanswer.com/uploads/testedtuff/2009-09-26_170108_pictures.jpg John's Avatar

    John

    Master A.S.E Automotive technician

    Satisfied Customers:

    4071
    A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
  • http://ww2.justanswer.com/uploads/RO/rodcuda/2011-7-25_224114_Donhoff1.64x64.JPG Neal's Avatar

    Neal

    Chevy Mechanic

    Satisfied Customers:

    2306
    Shop Owner and Mechanic on multiple makes.
  • http://ww2.justanswer.com/uploads/goodwrench9124/2008-11-09_220838_dscf0007.jpg goodwrench9124's Avatar

    goodwrench9124

    ASE Certified Technician

    Satisfied Customers:

    2041
    Ase Master Certified, GM Master Certified Tech. Awarded GM Top performer, Hybrid certified
  • http://ww2.justanswer.com/uploads/DR/drivefast1971/2012-1-12_172422_0009051tQKh.64x64.jpg Ron Z.'s Avatar

    Ron Z.

    - Chevy Tech -

    Satisfied Customers:

    1912
    18+yrs experience. State Inspector and Chevy Diagnostics