Freightliner trucks, like all other vehicles, have mechanical and other types of problems. These trucks have some unique problems that may sound difficult but end up easy to fix. Range shift inhibition is one of them. It is a safety feature that doesn’t allow a truck to move into reverse while driving. But if it happens in other situations, then it is an issue.
So, how can you fix range shift inhibited? When driving a Freightliner truck, you can sometimes notice a break in the transmission. If you are lucky, you can fix it by simply turning the truck off and on again. If the problem is mechanical, the most common fix is adding transmission oil. Sometimes a part of the transmission, like a valve or a sensor, needs replacing.
Stay with us if you want to know more about this frequent problem among freight liners and buses. We will cover the topics of troubleshooting and fixing the inhibitor. You will also know what the inhibitor is and its purpose.
What is a Shift Inhibitor & What Is It For?
A shift inhibitor is a safety feature on many trucks and buses. If the driver, while driving, tries to put the gear into reverse, the inhibitor will activate and stop it. When the inhibitor works properly, you will only get a message on the board when it is activated.
But, if the inhibitor is activated while driving, that can point to a mechanical problem. Sometimes the driver will notice that the gears are not shifting and that the RPM are too low or high. That is one of the symptoms of the problem with the inhibitor.
Pro Tip: It is valuable to know that most problems with the inhibitor will not put out any codes on the OBD scanner.
Common Causes of Range Shift Inhibited
The most common problem is low transmission fluid due to leakage. Sometimes the problems can be in the solenoids, range sensor, or worn transmission filter.
Low Transmission Fluid Level
The problem with the inhibitor is frequently connected to low levels of transmission fluid. You need to check the user manual for the type of fluid to use. Also, you need to know how much fluid to add. You can check with the mechanic if you are not sure how to approach this problem.
Dirty Transmission Fluid and Filter
If the problem is in dirty filters and transmission fluid, they must be replaced. The mechanic should check the fluid and the filter and replace them if needed. These things are replaced in intervals, so check when you changed them last.
Faulty Shift Solenoids
If your truck is often stuck in neutral and has problems with shifting gears, the problem can be in the solenoids. That is a commonly shared problem with the faulty shift inhibitor. Replacing it can cost more than $500, and it takes more than 3 hours to replace it.
Malfunctioning Range Sensor
A range sensor in communication with the Powertrain Control Module ensures the vehicle is in the right gear. If the vehicle doesn’t start, goes into limp mode, or is in the wrong gear, that can point to the problem with this sensor. A code for this problem is commonly P0705. This issue is sometimes connected with the shift inhibitor.
Wiring Issues
Wiring is a common problem with many different parts of the vehicle. Wherever you have wires, they can cause a problem that is overlooked. Sometimes the wiring is just bad, and the contacts are worn. Or there is a problem with corrosion. In either case, the wiring should be checked and fixed if needed.
Mechanical Problems in the Transmission
Several mechanical problems are usually connected to the transmission. The most common are problems with the clutch, bearings, valve body issues, half shafts, driveshaft seal, or even the engine. If the problem persists, the mechanic should analyze all these elements.
How To Fix Range Shift Inhibited?
We will analyze how you can test most of the components that can cause a problem with the range shift inhibited.
Check Out Don’t Get Stuck in Neutral: How to Fix Range Shift Inhibited Like a Pro:
Check the Transmission Fluid Level and Condition
Park the car on a flat surface. Locate the transmission fluid dipstick. Pull the dipstick out and check the level. Once you have done it, you can check the condition of the fluid. Place the dipstick on a paper towel. If it is in pink or red color, it is fine. If it is going toward brown, it needs replacing.
Inspect the Transmission Fluid and Filter
If the transmission fluid is turning dark, that is a sure sign to replace it. Also, it is worth knowing that the filter needs to be replaced every 50,000 to 62,000 miles. The filter is placed between the transmission pan and the tube, which regulates the pressure of the transmission fluid. It also blocks off the metal shavings and other dirt from contaminating the fluid.
Test the Shift Solenoids
To test the shift solenoids, you must lift the car with a jack and use a multimeter.
- Use the jack to lift the car. Find the transmission oil pan. Remove the bolts that are securing it. Under it is the solenoid connected to the transmission body
- Above the shift, the solenoid is two plugs. Unplug one and prepare the multimeter. Switch the multimeter to ohms and set the range to 200
- Use the black pin from the multimeter to touch the negative battery terminal. Test the plug you plugged out by touching the tab with the red pin from the multimeter. The multimeter should read between 12 and 25. Results above or below this show that the solenoids are bad.
Test the Range Sensor
There are several steps in testing the range sensor, and we will go through them.
- Do a visual inspection of the sensor. Check for contamination
- Check the encoder wheel for damage
- Read fault codes (P0705 – P0709)
- Check the resistance of the sensor. Use the ohmmeter. At 80 °C the value should be 1000 ohms
- Check the connecting lines of the sensor. Pull out the sensor unit and check the ground. Measure with the ohmmeter. The value should be up to 30 MOhm.
Check for Wiring Issues
Check that all wires are connected properly. Also, check the conditions of the wires.
Diagnose Mechanical Problems in the Transmission
These problems can come from several different parts, as we mentioned. Diagnosing these requires the help of a qualified mechanic.
FAQs
Where is the NSBU Switch on a Duramax?
The NSBU switch is mounted on the transmission’s selector shaft on a Duramax.
What are International Truck Transmission Problems?
The most common problems with international truck transmission are:
– Faulty solenoid
– Problems with shifting gears
– Leakage of transmission fluid
– Incorrect gear ratio
– Mechatronic failure
How much does it cost to fix range shift inhibited?
It depends on the cause of the problem. Oil and filter replacement can cost between $100 and $250. The mechanic should diagnose the problem, so you can know your problem.
Final Considerations
You already turned off your truck and tried turning it back up again. It didn’t solve anything. The next step is to check the transmission fluid and its condition. If that is also okay, the rest is in the hands of the mechanic. The problem can be in a solenoid, range sensor, or some other mechanical failure.
The best way to avoid these problems is through regular maintenance. The fluid and the filter are essential. Keep an eye on the service terminals; most of these problems will avoid you. Stay with us for other mechanical bits of advice!
