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How to Bypass Reduced Engine Power: Causes & Fixes

How to Bypass Reduced Engine Power
Last Updated on Aug 16, 2023 By Lillian Kazmierczak

When you are driving and feel the engine lag or start hearing noises, it can be accompanied by the reduced engine power or the check engine light. This is because your electric control unit has sensed the problem and forces the car to drive in limp-in mode.

Knowing the cause of these problems and how to fix them will keep your engine running for a long time. So here we look at what causes reduced engine power and ways to bypass it.

What’s Engine Power Reduction?

Engine Power Reduction

Photo Courtesy: YouTube

Your car’s ECU (electronic control unit) converts to reduced engine power mode when it senses a problem with the car that causes engine damage.

This shows on your dashboard as a “Reduced Engine Power” light on models that have this (GM cars) and a check engine light on models that don’t. Some call this limp-in mode.

These lights tell you that there is a failure in the system that requires your attention. Your car tells you to get it to a mechanic or fix the problem yourself.

Each car’s ECU system is different, so the symptoms are also different.

Causes of Reduced Engine Power

Causes of Reduced Engine Power

1. Faulty Mass Airflow Sensor

The mass airflow sensor tells how much oxygen the engine gets and then injects the proper amount of fuel.

If the sensor malfunctions or is grimy, the dashboard light will alert you to this issue.

2. Car TAC System

The throttle actuator control (TAC) regulates the car’s throttle and boosts the throttle when your car needs assistance. When the TAC is faulty, the dashboard light will come.

Generally, when this light appears, you have an issue with the electronic fan clutch or fuel system.

3. Oxygen Sensors

Your car needs to maintain the proper air-fuel ratio to run properly. The O2 sensors help the engine maintain this balance.

If the sensors malfunction, your dashboard light will let you know the engine takes in too much oxygen.

4. Connectors

Harnesses and cables wear out over time. When this happens, it can cause a reduction in your engine’s power.

You can check the cables and harnesses to ensure they are not cracked or loose. Replacing any loose, broken harnesses could fix the problem.

5. Clutch

The drive wheels and transmission receive engine power when you engage the clutch. So, a failing clutch can result in reduced engine power.

You will hear sounds and squeaks and feel a pulsing of the engine. This can be a transmission issue. Take the car to a mechanic immediately.

How to Bypass Reduced Engine Power

Tools You Need

  • Soft rag
  • Screwdriver; Phillips head and regular
  • Longnose plier
  • Toothbrush
  • Sandpaper

1. Examine the cables

You are looking for unhooked grounds and loose wires. First, disconnect your battery, then look for loose clamps, wires, and harnesses.

Next, reconnect unhooked grounds tighten loose cables and clamps. Finally, change out anything that needs replacing. Then, reconnect the battery.

2. Examine the Battery

Battery connections can loosen as you drive and become corroded.

Check the battery is fully charged and clean off any corroded cables and around the battery posts using an old toothbrush or sandpaper.

Make sure your cable connections are tight. If the battery doesn’t fully charge, you should replace it.

3. Unclog the Electronic Control Unit

A mechanic should look at a clogged electronic control unit. They can put in a new one or re-flash the existing unit.

4. Check the Oxygen Sensor

Clean the faulty oxygen sensor, being careful not to press too hard and ruin it. If it still is an issue after cleaning, replace it with a new one.

5. Check the Airflow Sensor

It is easy to clean the mass airflow sensor and check if it is working. You can clean it with a soft dry rag but don’t rub too hard.

The sensor sits between the air filter and manifold. If the sensor is faulty, replace it.

6. Check the Clutch Chattering Sound

Clutch chattering is usually an indication of low transmission fluid. If needed, check the fluid level and add new transmission fluid to the max level line.

7. Check the Throttle sensor

If the throttle sensor is the issue, you can replace the throttle body or the whole sensor. Neither one is costly, and the money spent will be worth it.

8. Catalytic Converter Clog

The catalytic converter reduces engine toxins like carbon monoxide, hydrocarbons, water vapor, and nitrogen oxides into less harmful emissions.

However, when the catalytic converter is clogged or not converting properly, it needs replacing. This repair is a couple of thousand dollars but needs doing and requires a mechanic.


1. How to reset the reduced engine power light?

The light can not be reset by flipping a switch or pressing a button. If the light should go off before you have it looked at, it doesn’t mean the problem is fixed. The problem that caused the light to go off needs fixing for the light to reset.

2. Will a bad ignition coil reduce engine power?

A faulty ignition coil can cause poor fuel economy, stalling, no-starts, affect how the car idles, high speed and under-load performance, and how your catalytic convert functions. These need looking into as they happen.

About the author

Lillian Kazmierczak

As far as I can remember, I would say I have been a car nut for my whole life. My father was a car dealer who used to change and repair his cars himself. This gave me the opportunity to get around all sorts of cars and get my hands dirty repairing vehicles from an early age.

A great fan of Japanese quality and German preciosity, my deep passion lies in older models that I believe have a flair that takes me back to my childhood! I also love their extraordinary durability and reliability when compared to today’s modern models.

When not out taking a ride, I enjoy socializing with fellow motorheads online and consuming any car facts and figures I can get my mind on!

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