The Blazer with the 3 button system which I just purchased has an issue with the 4 wheel drive. I have searched for the solution within this forum but still can not figure out the problem. To start off with I do not have a drivetrain scanner. Just a Large orange scanner which I bought from Autozone. Now, this is what the truck is doing; 1. None of the lights come on on the selector display with the exception of the 2WD light sometimes faintly glows and once in a while all three lights will wildly flicker for a second, mostly when I hit a bump. 2. There is no 4wd system warning light lit. 3. I do not get any flashes on the selector lights when I ground what I believe is the #13 pin in the OBD2 connector (near center bottom row?). 4. I have removed the 4wd fuse from the fuse panel as well as all the rest top ensure that none were blown (none were). 5. I tried like crazy to get the plug on the motor assembly on the side of the transfer unplugged but could not. The bolt just turned and turned in both directions no matter how hard I pushed it in or pull out on it. 6. Doing a voltage / ohms test on the wires I got the following readings;
No voltage on any of the wires with or without the key on or running.
Large Black wire: 12.4 ohms
Large red wire: 29 ohms
small brown wire: 30.1 ohms
small yellow wire: 25 ohms

Any and all help would be appreciated. BTW, where in the truck is the TCCM?

Andy

 

The TCCM is located behind the passenger side kick panel just ahead of the front door & just below the dash. Pull the TCCM and check the connections. From there, check resistance on the wires that run from the TCCM up to the switch. The thread linked to below has the wiring diagrams for the NV233 transfer case as found in your truck:

NV233 No Mode Switch (ie. 2HI to 4HI)

 

Thanks I will look further into the problem tomorrow.

Is the DLC a separate connector than the one I plug the scan tool into to check engine trouble codes? This OBD2 NV233 diagnostics readout states that the DLC is on the right side of the steering column.

 

Same connector. Positions may vary.

 

I grounded the #13 pin counting left to right starting with the top row. There was no other metal connector in any holes close on either side of it. No lights. Got busy doing other stuff yesterday so I did not get to test out the TCCM connection. When I pulled the plug there was one pin at the bottom of the plug which was slightly corroded. I will check further in depth today.

 

Test the main power & ground wires to the TCCM while you are in there measuring the resistance on each of the wires to the switch.

 

OK I have troubleshot the system per the NV233 no mode switch checklist.

First of all I feel that I need to bring up that the plug on the TCCM has 4 rows of connectors (2 rows with large holes and 2 rows of tiny holes down the center) as of which it looks to only have connections for pins to slide into on the outside rows. On the other hand the TCCM socket has two rows of pins which are very close together and look as though they would line up with the two middle rows of the plug. Could there have been a mix up of TCCM's in the past and this TCCM is not for the truck (year make and model) I have.

OK furthermore the check for ground on C10, D10, D12 and D13. First of all there is no D10 metal connector in the plug that I can see. All but D10 had solid grounds in the plug. The D10 has a solid ground through the TCCM when mounted to the body of the truck. Is this correct? All checked out with well within spec grounds.

C4 had 12 volts when 2HI was pushed and C5 had 12 volts when 4HI was pressed.

 

I just tested for trouble codes on the system. There were 2 orange wires on the vehicle diagnostic connector. I grounded one and it did nothing, no lights. I grounded the other orange wire which was in the corner of the connector and it immediately blew the cigarette lighter fuse.

As for the main power and grounds to the TCCM The following pins are hot when the key is off; C6, D14, D15 and the grounds are C10, D12, D13 AND D2

With the key on and not running the following at hot with approximately 5VDC; C14, C11 and D8 12 VDC on C1 10.3 VDC on D2 which with the key off was a ground. C12 had .6 volts

Any other ideas or should I already know what is wrong.

Thanks, Andy

 

Found a used TCCM at a local salvage yard for $20.00 and it fixed the problem.

Thank you for the assistance, Andy

 

how much would a new tccm cost. i have the same problem. cant find one at any salvage yards.