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 Jettadan1 Your Own Question
Jettadan1, Chevy Technician
Category: Chevy
Satisfied Customers: 5064
Experience:  Most of our fleet is chevy.
Type Your Chevy Question Here...
Jettadan1 is online now
A new question is answered every 9 seconds

97 chevy blazer: has electronic 4wd..It wont shift..front wheels

Customer Question

My 97 Chev Blazer has electronic 4wd. It wont shift into 4hi, and when I shift into 4lo, I feel the t-case shift but the front wheels get no power. can this be fixed easily and cheaply by myself. I am very mechanically inclined.
Submitted: 6 years ago.
Category: Chevy
Expert:  Jettadan1 replied 6 years ago.

Bulletin No.: 05-04-21-002

Date: March 10, 2005


Guidelines for Replacement of Transfer Case Control Module (TCCM)


2005 and Prior Light Duty Trucks


with New Venture Gear (NVG) Transfer Case (RPOs NP1, NP4, NP8)

Dealers are replacing the TCCM unnecessarily.

Dealers are replacing the TCCM with codes stored in HISTORY only. The TCCM does not have a current fault condition when tested.

Parts reviewed at the Warranty Parts Center (WPC) have a 75% No Trouble Found (NTF) rate. The only two legitimate reasons to replace the TCCM are:

^Diagnostic Trouble Code (DTC) C0550


^NO Communication with a scan tool.


DTC C0550

This DTC indicates that the module has an internal fault and should be replaced.

No Communication

^The no communication conditions referenced here are also caused by a module internal fault to a point where the module physically will not talk. A technician cannot pull DTCs from the module because it will not communicate. The module is electrically dead.


^No communication is not to be confused with a U1026 code. This code tells the technician that the module may still be functioning but is temporarily off line. This code may be set by the Instrument Panel (IP) or the Powertrain Control Module (PCM) against the TCCM. The technician needs to figure out why the module went off line. These are typically caused by connection concerns. There is no need to replace a TCCM for a U1026 DTC.


Diagnostic Aids

^When diagnosing a transfer case electrical control system, ALWAYS check power and ground wiring first.


^Test the connections for intermittent or poor connections, complete plug insertion, bent pins, pushed out terminals and water contamination.


Pay particular attention to the terminal connections at the module. Spread or open terminal connections may create an intermittent contact. Do a pin drag test. Refer to the terminal testing information in the table shown.

^After repairs are complete, ALWAYS clear DTCs from the module prior to a system function test. If codes are not cleared first, the system will not function after repair. The technician may erroneously think that the system is still down and that further repairs are needed.



Dealers who unnecessarily replace the TCCM that are found to have No Trouble Found (NTF) at the WPC will be returned to the AVM (Area Service Manager), or the DSM (District Service Manager) in Canada, through the Regional Feedback Process and may be charged back for the repair through the WINS system.







What this means is usually there is a fualt with the wiring or connections to and from transfer case. And you have fuses that could have blown

Expert:  Jettadan1 replied 6 years ago.
I am a chevy expert as well as a car expert and I have moved our question to chevy.
Customer: replied 6 years ago.
my scan tool is showing no codes for the 4wd, and I have replaced the fuse. the dash lights come on for BOTH 4hi and 4lo when shifted into 4lo. the lights flash and then go back to 2hi when 4hi is selected.
Expert:  Jettadan1 replied 6 years ago.
Have you gotten under vehical to check connections. All connections need to be followed to and from tranfer case. If you look good on the connection


  1. Lower instrument panel trim.
  2. Two screws securing the transfer case control module to the bracket.
  3. Electrical connector from the transfer case control module.


  1. Electrical connector to the transfer case control module.
  2. Two screws securing the transfer case control module to the bracket.
    • Tighten transfer case control module screws to 8 Nm (71 inch lbs.).
  1. Lower instrument panel trim.
s and they are clean then the control module may need to be replaced.



Customer: replied 6 years ago.
I can accually feel the transfer case engage in 4lo but there's still no power to front end, but it wont shift into 4hi
Expert:  Jettadan1 replied 6 years ago.

When that happened t me in my 4x4 it was just a vacum hose that came off. It was mounted by the front cross memeber. I am not sure if your electonic system involves vacum but you may want to try. There is an actuator switch down there also that could be the root cause. It going into low gear is different that shifting intoXXXXX

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... seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like
...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
< Previous | 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:

  • GM Tech (Cam)

    GM Tech (Cam)

    Chevy Technician

    Satisfied Customers:

    GM Grand Master Technician 2007. 14 years experience.
< Last | Next >
  • GM Tech (Cam)'s Avatar

    GM Tech (Cam)

    Chevy Technician

    Satisfied Customers:

    GM Grand Master Technician 2007. 14 years experience.
  • Tim's Auto Repair's Avatar

    Tim's Auto Repair


    Satisfied Customers:

    Have owned a repair shop for 25 yrs.
  • Gary's Avatar


    Chevy Technician

    Satisfied Customers:

    15 years GM master tech
  • Dave Nova's Avatar

    Dave Nova

    Chevrolet Technician

    Satisfied Customers:

    ASE Master Certification. GM World Class Certification
  • John's Avatar


    Master A.S.E Automotive technician

    Satisfied Customers:

    A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
  • Don 'Mo Lurch''s Avatar

    Don 'Mo Lurch'

    Auto Mech / Electronics

    Satisfied Customers:

    Chevrolet Cert., Heavy Line Mech, Race Shop Owner, Mobile Electronics.
  • Ron Z.'s Avatar

    Ron Z.

    - Chevy Tech -

    Satisfied Customers:

    18+yrs experience. State Inspector and Chevy Diagnostics