The development of automatic transmissions leads to the implementation of several safety measures. One of those is the neutral-start-back-up switch (NSBU switch). Its purpose is to block any attempt to start the vehicle from any gear other than neutral or park. But what if the car can start from all gears? Or can it not start from neutral or park? Then the NSBU switch can be the culprit. Is there a way how to reset the NSBU switch?
If the NSBU switch has moved from its position, it can be loosened and then returned to it. If the NSBU switch has a mark where the neutral/park position is, you can check did it move from it. If it did, you can realign it to its original position.
But, sometimes, the problem is not so easy to resolve. Before you even attempt to do this, you need to know if the NSBU is the problem. Also, you should learn how to maintain it properly when you fix it. We will cover all these topics, so stay with us.
What is NSBU Switch?
The NSBU switch prevents the car from starting from any other gear than the park and neutral. It also allows the transmission to move only one gear forward. It has two connectors. One is used to connect it with the transmission control module (TCM). The other is responsible for the power supply and the warning lights.
The NSBU’s main function is communication with the TCM. It is always informing it in which gear the transmission is now. If the TCM gets a signal from the NSBU about a transmission slip, it will send the vehicle into limp mode. That way, the transmission is protected from further damage.
The NSBU switch has other names like Park neutral position switch, internal mode switch, inhibitor switch, and range sensor. It is also connected with the range shift inhibitor warning on the dashboard.
Spotting The Signs: Symptoms Your NSBU Switch May Need Resetting
The main reason for an NSBU to fail is poor sealing. When that happens, the NSBU becomes susceptible to water contamination. Also, old age and overall wear will cause problems with the NSBU. Its work life can reach around 300,000 miles. Symptoms of failure include:
- The transmission is stuck in fail safe or limp mode setting
- The gear shift indicator on the dashboard is not showing the correct information
- The car won’t start
- The diagnostics show pressure switch codes (P0840 to P0876 and P1709 to P1714).
The most common issue is the limp mode. When that happens, the car is stuck in third gear. That way, the car is preventing further damage to the transmission.
Check Out 4 Signs of a Bad Neutral Safety Switch | Transmission Range Sensor:
Precautions Before Resetting Your NSBU Switch
A problematic NSBU switch may allow the car to start from any gear. That means that the car can suddenly go forward or back when the ignition is turned on. That can result in injuries to anyone nearby and damage to the car.
Before you try to reset the switch, disconnect the battery. You must eliminate any chance that a car moves in any way.
How to Reset NSBU Switch?
Resetting the NSBU switch is recommended in case you cannot start or even crank the engine. First, you need to locate the NSBU switch. It should be on the top of the transmission in 4WD models. While in the FWD cars, it is near the bottom of the transmission base. If you have a RWD car look at the left side of the transmission. The Allison 1000 NSBU switch is mounted on the transmission’s selector shaft.
Locate the two wires that are connected to the switch. One wire is connected to the “S” terminal and the other to the “I” terminal on the switch. Grab a pair of pliers and twist the wire to the “S” terminal in the clockwise direction until it is tight. Now, turn the wire to the “I” terminal counterclockwise until it is tight.
Reconnect the battery and start the engine. The NSBU switch should be restarted and working properly.
If the case that you can start or crank the engine, but the NSBU is not working properly, you may need to adjust it. This is done by sliding the switch. For this operation, raise the car on the jack, and call someone to assist you.
- Once you locate the switch, loosen it bolts just enough so you can move it sideways. You will need some basic tools like a ratchet and a socket for this. Some models will require some special tool that is usually cheap
- Tell the assistant to turn the key to the on position and then release it in case the engine starts to turn
- If you hear the engine, slide the switch toward the neutral or park position and tighten it with screws. They should be tightened to 18 to 21 lb/ft
- When the switch is safely tightened, start the engine twice. First, put the transmission lever in the park and then in neutral mode
- If the NSBU switch is not working, you can replace it. If everything is okay, lower your car from the jack stands.
Troubleshooting Common NSBU Switch Resetting Issues
The most common issue when resetting the NSBU is that you cannot get the car to start from park or neutral. If you tried resetting it and got nothing, the problem is usually in the switch. It could be old, worn out, or corrosion and water damage.
Professional Assistance vs. DIY: Weighing the Options for NSBU Switch Reset
If you have experience with car mechanics, you should be able to reset the NSBU switch. You can watch a Youtube video to get up to speed. But, if you are not so comfortable with your car mechanic skills, you should contact the mechanic. The process itself should not be expensive.
Testing the switch’s labor costs should not exceed $50 to $70. You can save that money if you are comfortable with the skills required for this operation.
Maintaining Your NSBU Switch Post-Reset
You cannot do much to prolong the NSBU switch work life. If you want, you can visually inspect it from time to time. The main problem with the switch is in the sealing of its housing. The water can sometimes penetrate it. You can check for leakage problems. You should also know the location of the fuse for the switch so you can check it.
Common Misconceptions About NSBU Switch Resetting
Sometimes drivers think that any problem with the NSBU switch can be resolved by resetting the switch. Sometimes, resetting will solve the problem, but you will need to replace the switch in other cases. It has its work life, and if it is worn out, you cannot do anything other than replace it.
FAQs
Can you start a car with a bad neutral safety switch?
Yes, you can. But, we would not advise it. When you do it, the car can start going in reverse or from a random gear. That can push the vehicle forward or backward, which can result in injuries to anyone close and damage to the car.
What happens when the neutral safety switch fails?
It depends on the case. Sometimes, you will not be able to start the car. In other cases, it will send the car into limp mode. But maybe the worst case is if it lets you start the car and you drive it. You will have a hard time controlling the transmission, and you may crash.
How long does a neutral safety switch last?
There are cars with 300,000 miles on the clock with the original NSBU switch still in place. But, in most cases, it will not last that long. You can expect to have problems after 200,000 miles.
Where Is The NSBU switch location
The NSBU switch is usually on or near the gearbox case, usually on the driver’s side. It checks the gear position for a safe start. To get to or replace it, you have to lift the car, take safety precautions, look at the service manual, or talk to a mechanic.
Conclusion
Maintaining the transmission is essential, just like maintaining the engine. There are a lot of parts that require your attention. One of them is the NSBU switch. You will have problems running or even starting the car if it is faulty. The TCM won’t know in which gear the transmission is, and you may drive backward instead of forward.
You can try to reset the switch. This can help when you can crank the car. If you cannot crank the engine, you must replace the switch. Luckily it is not that expensive. The part costs up to $100, while the labor costs can go to another $100. That money can save you from trying to resolve this issue by yourself. If you like to play around with cars, give it a go; at least visually inspect it. But do not drive with a faulty NSBU switch.
