01 Blazer Tranmission/ 4WD problem
 

Please help.
I encountered a transmission problem on my 01 Blazer (automatic trans). When I tried to drive the car this morning, it will only drive 5 mph and it will skip (not driving smoothly). Sudden onset of this problem. It does this in all gears (1, 2, 3, D, and R).

I noticed the 2-4wd switch light was initially on 4H (and I always use 2wd unless needed). I tried to switch to 2wd and the light would not turn on. Then I tried to go back to 4wd and now the lights are not lighting at all.

I'm assuming that the problem must be associated with the 2-4wd circuit. From reading the Chilton's Manual I figure this may be related to the 2/4wd selector switch on the dash, a broken transfer case control module, a poor wire connection, or the shift motor?
Can anyone help direct my troubleshooting or redirect me to what you think it is?
Thanks in advance!
-Steve
ps- in retrospect, the car has been a little slow to shift automatically for the past two months when accelerating...Winding up to higher rpm before finally shifting. Not sure if this is related or not.

additional thoughts
 

SO from reading some of the other forums, it seems that I have a few possible problems:
1) Transfer case switch on dash
2) Transfer case control module (TCCM)
3) Encoder motor (I'm not sure what this is yet-not in Chiltons manual)

Would a OBD2 diagnostic tester be able to tell me the problem? Or can I figure this out based on the car's symptoms?
thanks
Steve

3 or 4 button switch in the dash?
If 3 button, check out OBD2 Non-Automatic Transfer Case Diagnostics by lastcoupe & swartlkk
If 4 button, then an enhanced OBD2 reader will be necessary to access the TCCM via the serial bus communication network in the vehicle.

Almost sounds like you are stuck in 4LO...

great stuff! follow up questions...
 

Great stuff! I have a 3 button 4wd selector switch. I agree, it does almost feel like I'm stuck in 4Lo.
Three follow up questions:


Question 1:
Based on the car's symptoms, can a reasonable diagnosis be made (should I fail to figure out the proper way to check the DTC tomorrow after work)?
Symptoms:
-Car working fine, then one morning it would not drive more than 5-10mph and jerked constantly.
-Transfer case switch lights for 4wd are working intermittently, but the 2wd light never goes on.

Question #2:
What are the sequences for the Diagnostic Trouble Codes (DTC)?
I understand the three transfer case shift select buttons will blink when I ground the data link connector as described. What sequence exactly points to which DTC? In the posting it lists:
DTC 1: RAM
DTC 2: Encoder fault
DTC 3: TCCM motor circuit
DTC 4: RAM/ROM failure
Am I to assume DTC 1 is one light blink? DTC 2 is two light blinks? DTC 3 is three light blinks and DTC 4 is 4 light blinks?

Question #3a:
Is there another name for the transfer case encoder/motor?
(Looking thru the basic Chilton manual, there is no reference to a transfer case encoder/motor. Is this the same thing as the "Electronic shift motor"?)
Question #3b:
Is it necessary to replaced as one complete unit (encoder and motor) or can each be done individually as needed to save on cost?

Thank you very much for your expertise!
-Steve

1- lets see what you come up with from the TCCM first
2- You are correct.
3a- Chiltons, Haynes, etc aftermarket manuals SUCK. If you are serious about repairing your truck, get a FSM (factory service manual). They pop up on eBay every now and again for reasonable prices (not the $20 you paid on the paper weight Chiltons). But back to your question. Electronic shift motor would be the same as the encoder motor.
3b- You cannot replace one without replacing the other, nor would you want to.

DTC 2: Encoder fault.....Three follow up questions:
 

DTC 2: Encoder fault
First, thank you for directing me to the diagnostic test. Worked like a charm!

Question 1:
Where do I find the Transfer case encoder channels P, A, B, and C?
So using the OBD2 Non-Automatic Transfer Case Diagnostics provided, I received a DTC 2:
DTC 2: Encoder fault
The next step in the table is to check the Transfer case encoder channels P, A, B, and C to ground and measure the voltage, which will then direct me to replacing the encoder or the transfer case control module.
I looked under the car, the transfer case has only one electrical connector going to it, and the wires are labeled 1-8. Any direction on where to find these?


Question 2a:
Are both the encoder and the transfer case control module DEALER ONLY parts? I called around while at work to price check, and no one seems to carry them except the dealer. They both run about $400-500.

Question 2b:
SHould I buy a new TCCM or encoder, or a used one?
Given the cost I'm inclined to buy a used TCCM or encoder, however, given that there seem to be so many complaints with these components, I'm inclined to just dish out the money so I don't have a repeat (and stop paying for a rental car).

Question 3:
Does anyone have a digital copy of the factory repair manual for replacing the encoder motor?
Encoder motor replacement seems like it's going to be a bear. I only have the Chilton's manual, and it's naturally pretty skimpy (I am definitely going to buy a real manual in the near future).

Thanks a bunch!
-Steve
ps: sorry for the bold type, I can't seem to get it to go back to normal despite having adequate computer know how.

Have a read through the following thread:
NV233 transfer case / encoding motor switch by error_401
I have also posted the wiring diagrams for the NV233 in that thread as well.

2a - both are available in the aftermarket. Check out RockAuto.com.

2b - My vote would be for a new encoder motor. I do not believe that you need a new TCCM.

3 - The FSM is the best resource you can have at hand. AllDataDIY.com is a fairly economical choice if you have a laptop or computer in your garage. To replace the encoder motor, pull the front driveshaft and then unbolt the encoder motor. Reinstall in the reverse order.

2001 Blazer

Great! Making progress!
So I tested the system as directed above. Looks like it definitely is my transfer case encoder. There was voltage in the transfer case encoder channels which confirmed my Blazer was stuck in 4Lo (so the TCCM is working as suspected by swartlkk).

Question #1: Why is there such a HUGE price difference between aftermarket encoders and the Chevy dealer encoders? Am I missing something??
Chevy dealer costs $580. Aftermarket options from www.rockauto.com average about $140. Is the aftermarket missing something? The dealer version comes with encoder motor and encoder. The aftermarket options say only "transfer case motor". Does this include all required parts? From looking at the pictures, I think everything is there, but I won't be able to pull the part off the truck until tomorrow.

Question #2: Why are there so many variations in the aftermarket options (connector pin numbers etc) from www.rockauto.com?
All the rockauto.com encoder motors are listed to work for 1999-2005 (I have a 2001). The manufacturers are A-1 Cardone, Dorman, and Retech. Do I need to match up the connector pin numbers exactly? There are 2, 4, 5, 6, and 7 connector pin options. From what I remember, my connector had 8 connector ports of which 6 (maybe 7?) had a wire going to it. I called chevy with my VIN number and they gave me the OEM# for my truck's encoder. This OEM number matches only one of the rockauto.com options (a Dorman which is about $30 more expensive than the cheaper A-1 Cardone or Retech options). Of note, ONLY the Dorman gives the OEM number, so I feel like getting an A-1 Cardone or a REtech would be like guessing. Feeling pretty ignorant about this system, I'm inclined to get the Dorman because the numbers match (also has 7 wires in the connector which should match mine). Any thoughts?

Thank you much!
-Steve

The encoder motor is ONE assembly, not a separate encoder and separate motor. They are not sold separately at all.

One difference in cost is that the dealer is quoting you at MSRP and not at a wholesaler cost like most online stores quote. The other difference is remanufactured vs. new. I encourage you to haggle with the dealer. It'll get you better prices for better parts.

The OE# for your encoder motor is 15636696 with an MSRP of $573.58. The Dorman 600900 is the aftermarket replacement you would want if ordering through RockAuto.com. It sells for $147.79. GMPartsDirect.com has a new OE part for $340.

The only option you need to concern yourself with is that it is for the NP1 RPO code option or that it specifically states that it is for the NV233 transfer case.

Amazing with the quick helpful replies!
I will go with the aftermarket Dorman option for cost purposes. I didn't know dealers would decrease the cost with haggling! Good to keep that in mind for the next time.

I will let you know the results. Thank you again for your expertise! Having struggled through highschool teaching myself by rebuilding/repairing clunkers, I fully appeciate the Life Line!
-Steve