Q: My truck is stuck in 4L or 4H also the speedometer is saying I'm going 100 mph when I'm only going 20 mph. Is my GEM Module bad?

asked by on

Im not sure if the 4 wheel drive switch has gone out or the gem module is bad or if something else is wrong because my truck is acting like its stuck in 4H or 4L. And the speedometer is screwed up saying im going 100mph when im only going 20mph-25mph. Also the 4x4 is flashing on my dash when the switch is on the normal setting AW4WD but when I turn it to 4H or 4L it stops flashing and doesn't even light up on dash.

My car has 200000 miles.
My car has an automatic transmission.

Hi there. The issue could be with the output shaft speed sensor on the tail shaft of the transfer case. The output shaft speed sensor is a sensor the registers the speed of the output shaft and lets the computer (ECM) know how fast the vehicle is going. If the output shaft speed sensor is working properly, then there is an issue with the electrical wiring from the output shaft speed sensor and the dashboard. If you need further assistance with the speedometer and 4WD acting up, then seek out a professional, such as one from Your Mechanic, to help you.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. My truck is stuck in 4L or 4H also the speedometer is saying I'm going 100 mph when I'm only going 20 mph. Is my GEM Module bad?

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Speedometer not working

Hello there, you are correct. Both of the codes on your 2001 Hyundai Elantra can relate to the speedometer. The P0720 code is for output speed sensor circuit fault, this can be caused by a faulty speed sensor, a wiring...

Q: Will wheels from a 2016 jetta fit my suv?

Hello. Unfortunately these wheels will not work. Even if the bolt pattern was the same the offset and backspacing of the wheel would be wrong. This would cause some series issues in the way the vehicle drives if you were...

Q: Guage, fuel and thermostat needles moving very fast

You may have a connection that is getting corroded and is causing intermittent connection problems. If the problem happens again then have the connection to the dashboard cluster disconnected and then add dielectric lube to connection and pins. At the...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.