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goodwrench9124
goodwrench9124, ASE Certified Technician
Category: Chevy
Satisfied Customers: 3432
Experience:  Ase Master Certified, GM Master Certified Tech. Awarded GM Top performer, Hybrid certified
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I have a 2002 Chevy Trailblazer with the automatic 4wd ...

Customer Question

I have a 2002 Chevy Trailblazer with the automatic 4wd transfer switch on the dash. I noticed that the light on the transfer switch above the 2WD setting is constantly blinking and it looks like a Red "N" is illuminated to he right of 4Lo. When I switched to A4WDH, the light continued to blink on top of that setting. I parked the car for 20 minutes and started it again and the light was NOT blinking and the red "N" disappeared. Do you know what causes this blinking? What is the letter "N" appearing for? Jeff
Submitted: 8 years ago.
Category: Chevy
Expert:  goodwrench9124 replied 8 years ago.
Hello, the red {n} light is a indicator for a neutral position for the transfer case. the key here, is the 2wd light flashing, that indicates a problem with the transfer case system. the transfer case needs to be scanned for any trouble codes. i suspect one of two things, one is a switch problem. the transfer case switch do fail on these trucks. the other, there are several software updates for the transfer case control module. normally the software updates have to be programmed at the dealer with a class two scan tool!!!
goodwrench9124 and 3 other Chevy Specialists are ready to help you
Customer: replied 8 years ago.
Reply to goodwrench9124's Post: Does the red "N" light that indicates neutral mean that when I switch from 2WD to 4WD, it's not doing anything?
Expert:  goodwrench9124 replied 8 years ago.

normally if the transfer case was in neutral, this light would be on. then the truck would not move. i am pretty sure you will find the switch is causing you the problem. normally this problem will set a b2725 code in the transfer case module.

Transfer Case Shift Control Switch


Object Number:(NNN) NNN-NNNN Size: SH

The NVG 226 transfer case features a rotary 4 mode shift control switch located on the instrument panel. When the ignition key is in the RUN position, the transfer case shift control module monitors the transfer case shift control switch to determine if the driver desires a new mode/range position. At a single turn of the transfer case shift control switch, the lamp of the new desired position will begin flashing to inform the driver that the transfer case shift control module has received the request for a new mode/range position. The lamp will continue to flash until all shifting criteria has been met and the new mode/range position has been reached, or has been engaged. Once the new mode/range position is fully active, the switch indicator lamp for the new position will remain ON constantly. During normal driving situations, the transfer case can operate in the Auto 4WD mode. In the Auto 4WD mode, the transfer case shift control module monitors rear wheel slip speed, based on the inputs from both the front and rear propshaft speed sensors. When the vehicle experiences a rear wheel slip condition, the transfer case shift control module sends a pulse width modulated (PWM) signal to an electronic motor, which is the transfer case encoder motor. This motor rotates the transfer case control actuator lever shaft, applying a clutch pack. This clutch pack is designed to deliver a variable amount of torque, normally delivered to the rear wheels, and transfers it to the front wheels. Torque is ramped up to the front wheels until the front propshaft speed sensor matches that of the rear propshaft speed sensor. Torque is ramped down to the front wheels. The process would repeat if rear wheel slip is detected again. The NVG 226 transfer case has the added feature of also providing the driver with 3 manual mode/range positions:

4HI
4-Wheel Drive high range
2HI
2-Wheel Drive high range
4LO
4-Wheel Drive low range

The driver may choose to select any of these mode/range positions while driving the vehicle. However, the transfer case will not allow a shift into or out of 4LO unless the following criteria has been met:

The engine is funning.
The automatic transmission is in Neutral.
The vehicle speed is less than 5 km/h (3 mph).

This transfer case also has a Neutral position. A shift to the Neutral position allows the vehicle to be towed without rotating the transmission output shaft. Neutral position may be obtained only if the following criteria has been met:

The engine is running.
The automatic transmission is in Neutral.
The vehicle speed is less than 5 km/h (3 mph).
The transfer case is in 2HI mode.

Once these conditions have been met, turn the rotary switch clockwise past the last and hold for 10 seconds. When the system completes the shift to neutral, the red neutral lamp will illuminate.

Customer: replied 8 years ago.
Reply to goodwrench9124's Post: Ok. Thanks for your response. I'll get the switch replace this week.
Expert:  goodwrench9124 replied 8 years ago.
let us know how things turn out!!
Customer: replied 8 years ago.
I will. Thanks
Expert:  goodwrench9124 replied 8 years ago.
Lets us know how things turn out!! and Thanks for using JA!!!