car transmission in neutral

Neutral Safety Switch Symptoms, Function & Replacement

In Electric by Magnus Sellén6 Comments

A neutral safety switch is, as the name suggests, a safety switch that is a common component in vehicles with automatic transmission. These safety switches serve a simple purpose: to limit the vehicle to starting only in “park” or “neutral” gear.

What is a Neutral Safety Switch?

neutral safety switch

In contrast to the manual transmission, the automatic transmission does not have a driver-operated clutch or gearshift lever. With a manual transmission, a car can be started in any gear as long as the clutch is fully depressed, but when the clutch is not depressed and the car is in gear, the attempt to turn the engine on causes sudden jolts, as if the car is trying to go forward.

In both cases the car will still start, but it can be dangerous as drivers often forget that the gearbox is in gear and accidentally turn the engine on and cause a jolt.

With an automatic transmission this is prevented by a neutral safety switch. This safety switch prevents the ignition from being switched on at all when the car is in drive, reverse, or any other moving gear. Even if the driver forgets to put the car in neutral or park and cranks the engine, the engine will not turn at all, thus avoiding any danger.

Sometimes this neutral switch can become faulty, causing starting problems.

Signs of a Bad Neutral Safety Switch

Finding out whether a neutral safety switch is defective is relatively easy for someone with little knowledge of a vehicle’s internal systems. Here are the symptoms you need to look for to diagnose your car’s neutral safety switch:

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1. The ‘check engine light’ lights up

If your engine light is on and you happen to have an OBD scanner, you can check which code your car has indicated. If the code P084F is displayed, it means that your neutral switch is faulty, which should make the diagnosis fairly simple.

2. The car tries to startup in any gear

If you notice that your car’s engine is cranking even though it is in a moving gear, this definitely means that your car’s neutral switch is not working as it should, as it should not allow the engine to turn in any gear other than neutral or park. Your personal diagnosis cannot go any further, because further inspections can only be carried out by a real car mechanic with the right tools and precise knowledge of automatic transmissions and how they work.

3. The car starts only in ‘Park’ but not ‘Neutral and vice versa

Although it is better than having the car start at least in park, and not in another gear, in such a case the switch will still prove to be defective and you should not overlook the situation, but instead have it checked by a certified mechanic as soon as possible. There is no telling how long the neutral switch will last, so it is better to have it repaired or replaced before major damage occurs.

4. The car starts sometimes, but sometimes don’t

If you are lucky enough to have your car start only sometimes, it is still possible that your neutral switch is either completely defective or is threatening to fail. But in such a situation, the problem could be elsewhere, such as the ignition itself, the starter, or the wiring. In either case, you will need professional help to solve this problem. If you find that you can start your car before turning the engine on after shifting the gear stick several times, then your neutral safety switch is the culprit.

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5. The engine doesn’t turn on at all

An engine that does not turn on at all can mean many different things, from a bad battery to a faulty ignition and starter. You can check this by checking whether the dashboard light comes on after turning the key halfway. Unfortunately, for a thorough inspection you will need a specialist to examine your car to find the exact cause of the problem.

Testing & Solutions

Although there are a number of ways to diagnose the condition of your car up to a certain point, unfortunately you cannot carry out repairs or replacements yourself because access to the neutral switch or ignition is difficult. You should consult a trusted or known mechanic for diagnosis and repairs. There are a few things you could do to rule out other causes for the engine not starting:

Check Neutral Switch Parameters

With an OBD2 scanner you can check the parameters of the neutral switch to the ECM and transmission control unit. Ensure that the shift lever is correct and is set to the correct value for the desired gear.

Check your car’s battery

If your car does not start even when in park or neutral, you could check whether your battery is OK or not. The easiest way to find out is to check the lights on your dashboard. If the lights come on, your battery should be OK. Always try to charge it with a car battery charger first before doing anything radical.

Check your ignition

You should hear a click when you start the engine with the key. When you hear the click, your ignition is in operation. If you do not hear a click and your engine does not turn, it could be due to the ignition, although it is better to confirm your doubts by contacting a mechanic.

Check the engine’s starter motor

This can be somewhat difficult to check if you are not comfortable or do not even understand the basic components of a car. But if you know enough, you can check your starter by placing your hand on the motor, which is located quite deep inside the engine compartment under the engine block. If you feel any vibrations, your starter works. You can also check it with a voltmeter by checking the readings on the starter’s terminals.

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If none of these components are defective, then most likely your neutral safety switch is defective somehow, and you need a certified automatic transmission specialist to check the situation for you.

Neutral switch Replacement Cost

Depending on the make and model of a vehicle, the estimated average cost of replacing a switch is between $50 and $150. Labor costs can range from $50 to $100.

6 thoughts on “ Neutral Safety Switch Symptoms, Function & Replacement ”

  1. Thanks for the info! I kind of figured it was the problem while breaking it before pulling the transmission, due to needing a 3,4 clutch Pac! However my transmission problems became worse after the rebuild! It doesn’t want to move in any gear! Though I will check the amount of tranny fluid that is needed for my truck is what I’m hoping is the problem! For some reason my dipstick doesn’t sit all the way in, therefor making it impossible to get a reading!

    1. Author

      Thanks for your comment. There might be the wrong dipstick fitted in the car for that transmission? A faulty NSS can often cause the car to not engage any gears!

  2. Where is the neutral safety switch on a 2006 Mazda model 6,2.3 liter engine. Under the shifter when you remove the center console or under neath the vehicle in the front of the transmission.

  3. On the 2006mazda model 6 the car wouldn’t start sometimes unless you would jiggle it from left to right. Would nss be the culprit?

  4. So I have a 1994 CAD DeVille 4.9 engine had the starter checked have a brand new battery still the engine won’t turn over Iran codes current code says I 0 3 9 which I could not find in the codes website the engine, I hear the click for the ignition switch I don’t know what else to check can you please help me

  5. Due to very high demand and a high amount of comments, you might have trouble getting your comment answered by me. If you want to get fast answers from a certified automotive technician you should ask your questions here: Ask A Mechanic

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