The code 84 isn’t the regular error code that you see on diagnostic scanners. It is shown on the car’s instrument panel to indicate that the engine power is reduced.
So, why is the code 84 engine power reduced? It can happen if the throttle position sensor or the mass airflow sensor is bad. A clogged air filter or fuel system problem can also cause this code.
You need to take the following steps:
- Inspect the relevant sensors. Clean them and replace them if necessary.
- Clean the air filter or replace it.
- Check the fuel system for clogs. Replace fuel filters or pumps as required.
I will discuss the problems in detail and give effective solutions in detailed steps. Let’s get started.
Table of Contents
Code 84 Engine Power Is Reduced: The 4 Reasons and Solutions
The code 84 is activated when the critical engine components are at fault. Your car might go into limp mode when this happens. Check the detailed reasons below and find their solutions.
1. The Throttle Position Sensor (TPS) Is Faulty
The throttle position sensor measures your throttle input and sends it to the ECM. The Engine Control Module then controls the air-fuel input into the engine to deliver the right power. If the sensor can’t send accurate data because of wiring problems or damage, the vehicle will show the code 84.
But if you see the power reduced to a lower engine temperature message, that might be caused by a faulty temperature sensor.
How to Fix This?
- Check your vehicle’s user manual to find the throttle position sensor. Inspect the sensor visually for signs of dirt or grime. Clean the sensor and check if it works properly.
- Then, check the connectors and wiring for signs of loose connections and wiring damage. Tighten the connectors and repair any damaged wiring.
- If the message is still there, the TPS can be faulty. Replace the sensor, and the code should go away. You can use a diagnostic scanner to clear the code after replacing the sensor.
2. The Mass Airflow Sensor Isn’t Working
The task of a mass airflow sensor is to measure how much air is going into the engine. If the sensor is faulty due to dirt, grime, or damage, it can’t control the air flowing into the engine. So, the engine will have the air-fuel mixture in the wrong ratio.
This can throw the code 84 and reduce the engine power to protect the engine from damage.
How to Fix This?
- Locate the mass airflow sensor in your vehicle. It should be near the intake manifold. Check if there is any dirt or grime on the sensor.
- Use a good-quality sensor cleaner to clean the dirt. I suggest using the CRC Mass Airflow Sensor Cleaner for the best result.
- Then, check and tighten the connectors. Repair or replace the wiring if it is damaged.
- Finally, replace the mass airflow sensor if it is faulty. The code should now go away, and the vehicle power will be restored.
3. The Air Filter Is Clogged
Even if the mass airflow sensor is working fine, the airflow into the engine can be restricted due to clogged air filters. Over time, dirt and debris accumulate on the air filter. As a result, air can’t pass through the filter normally.
It changes the amount of air in the air-fuel mixture. So, the ECM reduces the engine power to prevent engine damage. Clogged air filters can cause a whole lot of other problems in your car.
How to Fix This?
- First of all, you need to check the condition of the air filter. If the air is partially restricted due to a dirty filter, you can use compressed air to clean the filter. Do it carefully so that you don’t damage the filter.
- But if the filter is fully clogged due to heavy dirt, you should replace the air filter. Remove the filter from its housing and install a new air filter of the same specifications.
- Do it carefully so that there is no gap between the air filter and the filter housing. Otherwise, you may hear a noise after changing the air filter.
4. Clogged Fuel Filter or Bad Fuel Pump
When the fuel filter is clogged, or the fuel pump is faulty, the pump can’t generate enough fuel pressure. As a result, less fuel goes into the engine.
It makes the air-fuel mixture leaner, and the performance drops drastically. The ECM may activate the limp mode and limit the engine power.
How to Fix This?
- You should check the fuel filter first. I recommend replacing the fuel filter every 20,000 miles. If the filter is at the end of its service life, you should change the filter.
- If the filter is still new but has dirt from contaminated fuel, you should clean it. Also, change the oil first if it is contaminated.
- Fuel pressure test kits are available out there. Take a kit and insert the fuel pressure gauge into the test port. Run the engine at different RPMs and check if the fuel pressure matches the recommended pressure on the user manual. If not, replace the fuel pump.
How to Clear Code 84 After Fixing Problems?
If you have resolved the issue but code 84 is still shown, you need to clear it manually. There are two ways of doing it.
Method 1: Using an OBDII Scanner
- Plug the scanner into the vehicle’s port.
- Go to Settings and find options like Clear Codes or Reset Codes.
- Select that option and confirm to clear the code.
Method 2: Resetting the ECU
- Turn the car off.
- Disconnect the battery. Remove the negative cable first and the positive last.
- Let all the electricity drain for about 30 minutes.
- Reconnect the battery cables in reverse order.
- Turn the car on. The ECU is reset now, and the code will disappear.
People Also Ask
The answers to some commonly asked questions about code 84 might help you a lot. Check them out.
Can I drive a car with the code 84 and reduced engine power?
Yes, you can still drive the car. But I suggest you pull the car over and check it for the cause. Once you diagnose the reason, you should solve it as soon as possible. It will ensure the engine can perform efficiently.
Does engine power reduction mean anything dangerous?
Not at all. You can see it as a safety system for the vehicle. When an engine component is faulty and causes damage to the engine, the system automatically enables the safe mode. In the safe mode, the engine power is reduced to lower the stress on it.
Conclusion
If the engine power drops suddenly and the code 84 appears on the driver’s display, it indicates the car has gone to safe mode. Faulty engine components can cause the ECU to throw the code 84 and reduce engine power.
I mentioned all possible reasons for this problem and guide you on how to solve this. If your vehicle shows this code, don’t get panicked. Get to a safe place and diagnose the system for faulty components.
Apply the solutions mentioned above to eliminate the problem. If you can do it correctly, the car will get its power back, and the code will go away.
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