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LMC Truck



 Page 2 of 2 <12
Username Post: S10/15, Blazer, Jimmy-Diagnostic information: 1991 & newer push button 4x4        (Topic#167344)
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3710
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
08-26-07 04:11 PM - Post#1240298    
    In response to kentuckian

You’re welcome, and thank you for the feedback.

It was nice helping when progress happen so quickly.


For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
LMC Trucks
Lefty469 
Forum Newbie
Posts: 1

Age: 53
Reg: 01-29-12
01-29-12 06:56 PM - Post#2184990    
    In response to Chevytech

Very glad to have found this site, and particularly this topic. Great work by both. Very informative and helpful.



 
flumperjumper 
Forum Newbie
Posts: 3

Loc: Georgia
Reg: 03-22-13
03-22-13 01:49 PM - Post#2328610    
    In response to Chevytech

Hi Chevytech,
I have a 99 Blazer with pushbutton 4WD controls. It will go into 2WD normally, also will switch into neutral normally. Any 4WD setting or auto, the light flashes and the front axles don't lock in. Transfer case seems to be engaging.
I was going to try getting the codes by your instructions by grounding pin #13 in the DLC. On my truck, pin #13 is open. No wire even going to the backside of it. I tried my OBDII scanner with no codes detected, as expected. "service 4WD" light is not on, except at initial startup as it should be.
Sorry for the epistle, but is there a pin I can ground on the 99 model or what? I appreciate any help.
Flumperjumper

Thanks,
Willie Jumper


 
flumperjumper 
Forum Newbie
Posts: 3

Loc: Georgia
Reg: 03-22-13
03-23-13 11:41 AM - Post#2328818    
    In response to flumperjumper

[quote=flumperjumper]Hi Chevytech,
I have a 99 Blazer with pushbutton 4WD controls. It will go into 2WD normally, also will switch into neutral normally. Any 4WD setting or auto, the light flashes and the front axles don't lock in. Transfer case seems to be engaging.
I was going to try getting the codes by your instructions by grounding pin #13 in the DLC. On my truck, pin #13 is open. No wire even going to the backside of it. I tried my OBDII scanner with no codes detected, as expected. "service 4WD" light is not on, except at initial startup as it should be.
Sorry for the epistle, but is there a pin I can ground on the 99 model or what? I appreciate any help. It is a 4.3 stock. Engine with automatic. No alterations.
Flumperjumper[/quote]


Thanks,
Willie Jumper


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3710
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
03-24-13 08:11 AM - Post#2329075    
    In response to flumperjumper

Flumperjumper, on newer trucks like yours, with no wire at position 13 of the ALDL, that have the auto4hi feature, the diagnostic is done with a scan tool. Low price scan tools will not do this.

I will make a few more comments here because this is now a sticky at the top of the board and so many people are finding it when searching for help. I hope it has help a lot of people.

There are several different 4x4 systems that share some of the same parts.

I like the Manual lever system that uses a shift lever on the floor the best, but even this system has weak points and common failures. This system uses the 231 transfer-case. The most common issues are the vacuum switch on the top of the transfer-case, and the vacuum hoses getting damaged. The ruptured vacuum diaphragm that pulls the cable to engage the front axle is a less common failure.

The 233 transfer-case was used on the first push-button used in the S/T trucks. The “encoder-motor” is a weak point. The position sensor fails and the system does not know what to do because it cannot detect what position the transfer-case is shifted into. I know the first year a replaceable position sensor was used was 2003 in the full-size trucks, but am not positive that was the first year for the little trucks. These trucks also have a common problem of corrosion at the TCCM terminals. The dash switch is problematic. On some vehicles the insulation on the wire harness rubs through on a pinch weld underneath the truck by the transmission, but this is not very common. The vacuum switch on the top of the transfer-case fails just like it did on the earlier system. This system has the same vacuum hose problems and front axle diaphragm issue and the earlier system.

I am no fan of any of the push button systems on the S/T little trucks or the C/K full size trucks.

The systems with Auto 4 Hi systems are something I don't ever want to own. I think they have just to many weak points in the system.

For those of you like Flumperjumper, that have a auto 4WD system, good luck. Look at the components for an obvious problem, and if you don't see an obvious problem, bring it to some with a scan tool that understands the system.




For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
flumperjumper 
Forum Newbie
Posts: 3

Loc: Georgia
Reg: 03-22-13
03-24-13 10:19 AM - Post#2329120    
    In response to Chevytech

Thanks for the helpful info. I agree with you about electronically controlled systems whether pushbutton or turn knob. I will find someone with an appropriate scanner and let you know what, if anything I find that way. If not, I will follow your helpful posts in troubleshooting components. This is my first 4wd without an extra shifter on the floor. I do miss it! again, thanks for the good help. Will advise.

Thanks,
Willie Jumper


 
CaptnTony 
Forum Newbie
Posts: 60

Age: 52
Loc: SE MN
Reg: 11-12-08
04-14-14 12:32 PM - Post#2444547    
    In response to Chevytech

What I have is a 2002 Blazer LS which, since it's transmission rebuild last year, has no 4wd control.

The initial 4WD issue was fixed by putting in a new safety neutral switch about 4 years ago. Because I was getting a newly rebuilt transmission, I purchased a new safety neutral switch (the original was, ummm, abused a bit during installation because I didn't know the proper trick to get at it...so it cracked in the corner. It worked fine, for awhile) to have installed by my mechanic. It has never worked since it was reinstalled. I'm finally thinking about attacking that issue again (after an overheating then no heating problem over the fall and winter).

My symptoms are:
1. When starting the truck, all three lights on the control switch (2WD, 4WD High, 4WD Low) blink once quickly.
2. Once running, none of the lights are lit.
3. None of the lights turn on/off when pressed after vehicle started.

It's been awhile since I've tried messing with it as I didn't want to break anything before knowing what to do next. As I recall though, I could hear the actuator 'kicking in' (at least a noise of some sort) when I pressed the 4WD buttons. Nothing would happen though, the vehicle did not switch into 4WD (not 'completely' at least from what I could tell). I've had mileage (mpg) issues with it since it started throwing EVAP error code - getting between 10 and 12 city driving and only about 14 with all highway. I noticed while I was making a u-turn in a parking lot a bit of the '4WD jumping' on sharp turns. I'm wondering if it's always in 4WD. I put 4 new tires on before winter, and haven't been able to 'fish tale' in all this snow very easily.
I never put it all together until that jumping feeling. I don't recall ever getting that in 2WD. Just wondering if somehow it's in (and out) of 4WD (slipping) somehow because I screwed around pushing the 4WD hi and lo buttons.

I haven't had it up on a lift to see if wheels all turn when in drive or anything like that yet. I'm wondering if there is a way to check if the vehicle is actually in 4WD somehow by mistake.

But, more importantly, wondering how to check the various components. I recall reading that there is a vacuum pump (actuator) under the battery somewhere that should be activated by the switches in the cab. If that doesn't work, then probably a vacuum leak somewhere. Then there must be a connection (cable) from that to the transmission 4WD (solenoid?). I don't know how to test that. And, of course, there's the Safety Neutral switch board. As I recall, I had the choice of two different Safety Neutral Switches the last time I bought one. I *may* have purchased the wrong one that was then installed onto my transmission when it was out of the truck. Is there a way to determine which transmission I have in the truck so I can purchase the correct one if necessary?

Thank you for your help. You've helped me in the past and I truly appreciate it.


*** I have tried, with no success, the OBD test outlined here. I couldn't get the lights to light up at all. Maybe it was me and my alligator clips not making full contact. Will try again when I get a chance. Being an amateur, with little to know experience, should I be able to just plug it into the proper port (13 I think it was without looking back) and then clip one labeled 'ground' right on the OBD (one right above it if I recall correctly)

**** Correction, if i start truck (still no lights) and shift to neutral with foot on break and push either the 4Hi or 4Lo buttons, both the 4Hi and 4Lo lights light up. I press the 2Hi button and those two lights go off but the 2Hi light never comes on. I can't hear anything from inside the truck so not sure if anything is actually happening other than electronically.



Sorry if I'm posting to a 'dead' thread. I can create a new one if that is better.


Todd

Current Victim:
--------------
2002 Blazer 4dr 4WD

Past Patients:
-------------
1957 BelAir Hardtop - 2dr
1957 BelAir Sedan - 2dr
1988 Blazer 2dr


Edited by CaptnTony on 04-14-14 12:35 PM. Reason for edit: No reason given.

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3710
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
04-15-14 05:42 PM - Post#2444938    
    In response to CaptnTony

If you read the thread, then you are not understanding what is in it.
I will give this instruction anyway.

You did not say if the truck will actually make it into the 4wheel low range. This would be the second test someone with experience would do. The first test would be to see if it gets into 4WD high. If you can't tell the difference in ranges, you are in over your head.

If the truck has set a trouble code, then four wheel drive high range will no longer work, until the code is cleared.

The lights on the switch illuminated when the during start up so the lights and the wires to them are working, yet the system is not displaying which position the transfer case is in.

There is a problem with the TCCM (Transfer Case Control Module), the Encoder, or the wiring between them.

As stated in this thread, for a truck as new as your truck, you need a scan tool to read the codes. Stop trying to jump terminals. You could use a multimeter and the wiring schematic to test the wiring, and encoder, and if you understood it, you would have a good chance of being able to find the problem.

The encoder is a weak spot in the system, and if it has failed to indicate the transfer case is in the two wheel drive position, the TCCM can not display that it is in two wheel drive. This would be my first guess of what the problem is but it is only a guess.

If I were working on it I would read the code with a scan tool. If I had to work on it without a scan tool I would use a meter and the schematic to test the encoder circuits through the wiring at the TCCM.

Don't worry about other parts of the system if it will not display what position the transfer case is in.







For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
LMC Trucks
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