Hi, I have a problem with the NP124 transfer case in my Saab 9-7X 4AWD. I replaced the transfer case motor because the old one wasn't responding and wouldn't engage the front wheels. Now it engages the AWD and stays in that position all the time. What could be wrong?
Saab 9-7 X, NP124 problem stuck 4AWD mode.
- Thread starter Shindoid
- Start date
Welcome to GMT Nation...
While the Text Book GM and GMC Diagnostics may be found in the OEM Service and Shop Manuals...much Diagnostic Information may be found in THESE PDF Documents and these Two Images will probably be very close to the 4WD Shifter or Switching Mechanisms in your Saab 9-7X.
In spite of the differences in the Car Line and Truck Line Series... there are only so many mechanical differences present within these Transfer Cases. Hope This Helps with your DMM Probing and Measurements:
A Decent, Generic Diagnostic Approach... (Ignore Physical Differences...it is the IDEA of How to Discover Problems and a Hands On View of the Environment)
While the Text Book GM and GMC Diagnostics may be found in the OEM Service and Shop Manuals...much Diagnostic Information may be found in THESE PDF Documents and these Two Images will probably be very close to the 4WD Shifter or Switching Mechanisms in your Saab 9-7X.
In spite of the differences in the Car Line and Truck Line Series... there are only so many mechanical differences present within these Transfer Cases. Hope This Helps with your DMM Probing and Measurements:
TRANSFER CASE STUDIES: DIAGNOSING GM’s 4WD SYSTEM - … / transfer-case-studies-diagnosing-gm-s-4wd-system.pdf / PDF4PRO
front axle motor actuator next. Using a voltmeter, I determined 0 voltage was present on terminal C, (circuit 241, brown wire). I chose this wire based on the wiring diagram, which showed fuse 24 in the IP fuse box feeding voltage to the front axle motor. Going this far without first checking...
pdf4pro.com
A Decent, Generic Diagnostic Approach... (Ignore Physical Differences...it is the IDEA of How to Discover Problems and a Hands On View of the Environment)
Last edited:
Please ignore @mrrsm 's post as you have the non-selectable AWD system. Not the same system as the one with the regular switch selectable 4x4 system.
How do you know the front wheels are staying engaged? Are you getting crow hop while making a sharp turn on dry asphalt?
Is the service AWD system light coming on? Are you able to scan for codes on the system beyond what a cheap scanner is able to scan? What brand and model encoder motor did you get? It might be possible that you got the one for the selectable 4x4 system, which incorporates a brake that the TCCM would not know how to handle but I think the connector might not match (two less wires).
How do you know the front wheels are staying engaged? Are you getting crow hop while making a sharp turn on dry asphalt?
Is the service AWD system light coming on? Are you able to scan for codes on the system beyond what a cheap scanner is able to scan? What brand and model encoder motor did you get? It might be possible that you got the one for the selectable 4x4 system, which incorporates a brake that the TCCM would not know how to handle but I think the connector might not match (two less wires).
Another thing I just through of. If there is a good difference in tire size front to back, the TCCM might be constantly engaging the front wheels thinking there is wheels slip. It uses front and rear output shaft rotation speeds to detect slip. Do you have a scanner capable to looking up the front and rear shaft speeds?
I know the AWD is engaged because I drove on ice and then on dry asphalt. The rear differential became noisy above 60 km/h. The car was locked in P and D, which caused the engine revs to drop and caused it to shake. AWD light didn't come on.
The new encoder motor is a Dorman 5-pin, for a single-speed transfer case, NP 126. Now I need to measure the wheel circumference. I'll have access to Tech2 soon, so I can scan the truck.
I've never seen or heard of a transfer case issue, either the AWD or 4x4, prevent the shifter from working. I've driven all of my 4x4 trucks in 4hi, which would be the same as the AWD staying engaged, on dry asphalt and the shifter was never affected except that maybe the truck lurched a bit as the front and rear drives were bound up and the parking pawl released hard. Also never heard the rear diff become noisy.
I would remove the encoder motor and let the transfer case release itself, which it should while driving. If it does, I would suspect the new encoder motor as bad (just because it's new doesn't necessarily mean it's good). If still getting the symptoms, try to move the shifter shaft with some pliers to see if that releases the front driveshaft. If the front driveshaft is still not free to turn with the front wheels in the air, I'd remove the front drive shaft just to confirm this releases the front wheels and symptoms disappear. If the symptoms do disappear, I'd look at the transfer case.
Noises could also be caused by a bad front or rear diff or the front disconnect, which doesn't disconnect, is bad. Another possibility is something with the tranny.
Did you try pulling the fuse (Fuse 8) if that doesn't work i would think best guess is scanning it with the tech2 when you have that access
Thank you for your valuable advice
How does the transfer case release work? Is it automatic? I've heard of some kind of spring on the transfer case clutch. What position should the transfer case shaft be in when the AWD is engaged and only rear-wheel drive is available?
After the encoder motor engages the front wheels, because of a lack of a brake like in the 4x4 transfer case, it slowly returns to the 2WD position on its own. Don't know if it's a spring or it's just a natural way that it works but it does that. I saw this first hand when the rear diff grenaded on my 9-7x and only had the front wheels. The rear driveshaft was free-spinning and the front wheels were constantly engaging and disengaging. I tried to pull the fuse after the front wheels were engaged and it would move for a while until it started slipping the front wheels and stopped moving. I had to put the fuse back and had the constant engaging of the front wheels, basically slip/bang.
Found it! Located on Charm.li.
NVG 126-NP4 Transfer Case — 2005 Chevrolet TrailBlazer 4WD L6-4.2L VIN S Service Manual | Operation CHARM
Detailed repair manual for the 2005 Chevrolet TrailBlazer 4WD L6-4.2L VIN S.
charm.li
So if I read this right, clockwise is to apply (AWD) and counter clockwise is to release (2WD).