Have a 236 that shifts into 2 high, 4 high, and AWD. But, it won't go into 4 low. Button push gets flashing light till it reverts to prior range. I have multiple motors and TCCMs that have been tried and same result.

Is it possible there is still an electronic problem or is something going on in the transfer case? I have tested the wiring from the TCCM to the motor and it's all good.

All the issues I see for the most part involve not shifting into 4WD at all.

 

Hm.. dunno what is '236' but if it's a Blazer - then you have to check the vacuum lines that go from an actuator located under the battery shelf , passing the back side of the engine nearby the distributor and ends at the brake booster. The actuator is driven by a vacuum. If the vacuum is insufficient, the actuator will not pull the mechanical link in time and the operation is ceased.

 

236 is NP236 transfer case which is the 4-button with "Auto".

At this point I would take the encoder motor off and see if you can click through all the positions with a wrench on the shaft.

Some Blazers like to be rolling slightly 1-2 mph with trans in neutral before they will shift to low. This is per owners manual, yet many will report no problem with the vehicle just sitting still. Mine needs to roll. Probably because I very seldom use it and its sticky I suppose.

Just curious why you need low range so badly!!

 

I had a similar issue with a 2001 ZR2, and it ended up being the switch that was causing the problem by sending the wrong signal to the TCCM preventing it from going into 4-Lo. It requires a high-end bi-directional OBDII tool to read the TCCM codes to properly diagnose it though.