Isuzu NPR Transmission Light Flashing – Why? And What to Do?

There are several reasons why the transmission waring light on your Isuzu NPR is flashing. The thing you need to keep in mind is that your transmission could have developed a problem. So, to be sure, you should have your truck checked by a professional mechanic immediately. 

Transmission warning light highlights

• Common reasons:issues with the transmission or transmission control module
• How to fix:get the car towed to the dealership or repair shop
• Possible consequences:transmission may break
• Priority level:High
• Can you drive?Not recommended
• DIY repair:Impossible
• Repair price range:$300-$4,500

Isuzu NPR Transmission

One of the essential parts of a vehicle is the transmission. Thankfully, the NPR is equipped with one of the market's most reliable, advanced transmission units.

The truck is equipped with Aisin heavy-duty six-speed automatic transmission. With PTO capabilities, the Aisin transmission is engineered to work effectively with the Isuzu NPR diesel engine to deliver industry-leading performance and fuel economy.

However, despite its solid engineering, the NPR Aisin automatic transmission has its fair share of failures.

Why Isuzu NPR Transmission Light is flashing

1) Wrong or Low Transmission Fluid

All Isuzu NPR trucks manufactured in 2007 and later use one of the most inexpensive transmission fluids in the market. Although this silicone-based fluid is quite affordable, failure to use it could cause many problems for your truck. If you mistakenly add the wrong ATF in your Isuzu NPR, it'll burn up the transmission system in a day or two.

When you use the wrong fluid, and it starts burning up the transmission, the computer system in your vehicle will sense the issue and illuminate the transmission warning light. It is essential to keep record of the fluid you add to your transmission. This will help you to fix the "wrong ATF" error before it damages the entire transmission system.

Low Transmission Levels

Low transmission fluid levels are another severe issue that can cause the transmission light to start flashing. When the ATF is down, your NPR will not produce the required hydraulic pressure, which could lead to a problem called gear slippage. Gear slippage causes your vehicle not to accelerate properly.

Transmission fluid works as a coolant and lubricant for the transmission's internal components. If it goes too low, the transmission will overheat and develop other problems from friction and wear and tear of the internal components.

When these problems arise, the Powertrain Control Module or the Transmission Control Module will sense the abnormality inside the transmission and illuminate the warning light. It is important to note that having a low transmission fluid level indicates a leak in your  NPR transmission system.

2) Overheating Transmission

You probably already knew about engine overheating, but did you know that your transmission could also overheat? It is perhaps the reason your Isuzu NPR transmission light is flashing. Overheating transmission is a severe problem that shouldn't be taken lightly. If your transmission is overheating, there's a list of possible underlying issues in the system.

If your truck develops this problem, it is advisable to have it inspected and fixed by a professional mechanic immediately.

Your Isuzu NPR is built with a transmission temperature sensor in the transmission valve body. The function of this sensor is to monitor transmission fluid temperature. The sensor is designed to warn you when the ATF gets unusually hot. If the transmission light is flashing and you suspect your transmission is overheating, you shouldn't drive your NPR beyond the closest service center.

An overheating transmission could mean damaged internal transmission parts or transmission fluid leakage. Low ATF levels and dirty fluid could cause your NPR transmission to overheat. Feeding your truck too much transmission fluid is another possible reason your transmission is overheating.

Here are a few possible reasons your transmission is overheating

• Damaged internal parts of the transmission.
• Low or excess transmission fluid.
• Dirty transmission fluid.
• External causes such as driving in extremely hot regions, stop-and-go driving, etc.
• Overheating engine, which strains the transmission, causing it to overheat too.
• Bad driving habits such as aggressive acceleration or overloading your truck.

3) Failed Components inside the Transmission

The Isuzu NPR uses an automatic transmission, a complex mechanical machine comprised of many parts. If one of these parts fails, your vehicle's powertrain control module will sense the problem and illuminate the transmission light.

One of these internal parts that are crucial to the proper functioning of the transmission includes the gears, which could wear out. When they do, you will hear noises whenever your vehicle shifts to another gear.

If the transmission light on your NPR is flashing due to worn components such as the gears, brace yourself for a costly repair job. Internal system failure in your transmission could result in power and torque loss.

The key to understanding transmission internal system failure is to know that a transmission is a complex machine with many parts; clutches, pistons, metal drums, and many others. This is also why you should have your truck inspected by a professional mechanic once the transmission warning light comes on.

4) Clogged Transmission Filter

The transmission filter is a small yet crucial part of the transmission system. It is designed to clean the ATF before it passes through. The primary function of the transmission filter is to keep contaminants from wearing out or damaging internal parts of the system. When this component becomes clogged, it restricts the free flow of the ATF; as a result, the powertrain control module may sense an issue with the ATF level and illuminate the transmission light.

Besides the transmission light flashing, you may experience performance issues with your Isuzu NPR if the transmission filter is clogged.

Other symptoms of a clogged transmission filter are:

• Burning smell.
• Noisy when in neutral.
• Leaking transmission fluid.
• Unexpected rattles.
• You may also hear whirring or whining noises instead of rattles.

What to Do When Isuzu NPR Transmission Light is flashing

The transmission takes the energy generated by the engine and delivers it to the wheels, enabling your Isuzu NPR to move. It is a crucial part of your vehicle and one of the most expensive to repair when it develops serious issues. A transmission system may fail for several reasons - just as many as there are parts inside of it. Even so, it's always almost better to replace than to repair it.

What do you do when the transmission light comes on?

If your Isuzu NPR transmission light is illuminated and flashing, you should rush your vehicle to the nearest professional mechanic to check it. As I already highlighted, the NPR is equipped with Aisin heavy-duty six-speed automatic transmission. It is one of the most advanced in the market, making it expensive to repair.

If you act fast and have your vehicle checked before the problem escalates, you can salvage your transmission system and avoid the heft costs of replacing the entire unit. Fixing minor issues like low transmission fluid levels could save internal components damage caused by overheating.

Your mechanic will scan your vehicle's computer system for any trouble codes to help determine the exact cause of the transmission light. Although you can check transmission fluid levels and top up if needed, the reason for the low levels is what you should be concerned about.

How to Take Better Care of Isuzu NPR Transmission

The best way to stay ahead of the issues causing the transmission light to illuminate is to take good care of your transmission. With these tips, you may never have problems with your transmission system.

• Check the transmission fluid levels regularly. This will help keep your transmission from overheating. The ATF is the blood life of your transmission system; if you maintain the proper levels, your NPR may never experience severe transmission issues. In your truck, low ATF levels will cause gear slippage, delayed gear engagement, and harsh shifts.
• Don't overload. The Isuzu NPR is a workhorse truck, and you may be tempted to overload it. This is dangerous to your automatic transmission. Always ensure you do not exceed the weight limit of your NPR. Overloading of any vehicle is one of the primary causes of transmission failure.
• Use recommended transmission fluid. As mentioned earlier, all Isuzu NPR models built in 2007 and later use silicone-based ATF. Using the wrong transmission will bring your entire transmission system down in days.
• Follow your mechanic's service schedules religiously. Many times our vehicles die from within because of negligence. Many people remember service schedules when the car develops a problem.

Transmission fluid should be changed regularly. You can check the manufacturer's manual for the recommended ATF changing schedules. Consult a professional mechanic if your NPR doesn't have such a recommendation.   

Conclusion

Your Isuzu NPR transmission light could be flashing for several reasons. The causes range from overheating and wrong transmission fluid to unacceptable transmission fluid levels. If this light comes on and you have no idea what is causing it, it is highly recommended that you have your vehicle checked by a professional mechanic.

There are several ways to prevent the issues that cause this warning light to illuminate. These include checking the transmission fluid level, using the correct transmission fluid, and getting regular service.