Troubleshoot Engine

Symptoms of a Bad Ignition Control Module: What You Need to Know

symptoms of bad ignition control module

If your car is not starting or running poorly, there can be many potential culprits. One possible cause is a bad ignition control module, which controls the ignition coils that generate the power needed to trigger the spark plugs that ignite the fuel in the engine.

If the ignition control module fails, it can cause a range of symptoms that can vary depending on the make and model of the vehicle.

Some common signs include engine misfires, stalling or hesitation during acceleration, difficulty starting the engine, and a decrease in fuel efficiency.

Other symptoms may include rough idling, backfiring, or a loss of power. In some cases, the check engine light may also illuminate on the dashboard.

6 Common Symptoms of a Bad Ignition Control Module

A bad ignition control module is usually associated with symptoms that are related to the performance of the engine.

The ECU receives input from various sensors and switches in the engine, such as the crankshaft and camshaft position sensors, and uses this data to determine the correct timing for spark plug firing.

The ECU then sends a signal to the ignition control module to trigger the ignition coil and produce the spark that ignites the fuel-air mixture in the engine’s cylinders. The ECU is responsible for managing and regulating many aspects of the engine’s performance, including the ignition system, and plays a critical role in ensuring that the engine runs efficiently and smoothly.

Ignition control modules can fail for a variety of reasons, including excessive heat, damage due to engine vibration, and sometimes age. When it fails, it can cause a range of symptoms, including misfiring, stalling, and poor performance.

It is important to replace a faulty ICM as soon as possible to prevent damage to other components of the ignition system. Here are some common symptoms of a bad ignition control module in more detail.

1. Engine Misfires or Stalls

One of the most common symptoms of a bad ignition control module is engine misfires or stalls.

The ignition control module is responsible for controlling the ignition coils that control the timing and duration of the spark that ignites the fuel. If the module is faulty, it can cause the spark to occur at the wrong time, or not at all, which will result in misfires, stalling, and other performance issues.

Other faulty ignition-related components, such as spark plugs, spark plug wires, and ignition coils, may also cause engine misfires so it’s important to rule these out when trying to get to the root of the problem.

2. Difficulty Starting the Engine

If the ignition control module is failing, the car may have difficulty starting. The engine may crank but not start, or it may start and then stall immediately.

If the module is faulty, it won’t properly control the ignition coils and they won’t be able to create a spark at the right time or at all. This can also make it difficult for the engine to start.

It’s worth noting that other factors, such as a weak battery, a faulty starter motor, or a clogged fuel filter, may also cause difficulty starting an engine.

3. Poor Fuel Economy

A bad ignition control module can also cause poor fuel economy. When it is not working correctly, it can cause engine misfiring, which means that the fuel-air mixture in the engine’s cylinders is not being ignited correctly.

This can result in incomplete combustion of the fuel, which leads to wasted fuel and reduced fuel economy.

A faulty ignition control module can also cause other issues with the ignition system, such as a weak spark or no spark at all, which can also lead to poor fuel economy, as the engine will be running rich, which means it is consuming more fuel than necessary.

4. Loss of Power or Acceleration

If the ignition control module is failing, the car will probably experience a loss of power especially when accelerating.

The ignition control module is responsible for regulating the timing of the spark plug firing, which is crucial for the complete combustion of the fuel mixture in the engine.

If the module is not functioning correctly, it can cause misfiring or weak sparks, which can result in incomplete combustion. This will lead to reduced power output and poor acceleration.

Additionally, a faulty ignition control module can cause other issues with the ignition system, such as intermittent stalling, which can also affect the engine’s acceleration.

5. Check Engine Light is On

Another common symptom of a bad ignition control module is a check engine light.

The ECU monitors all parts of the vehicle via sensors, including the ignition system. This ensures that the engine is functioning correctly and running as efficiently as possible.

If the ECU detects a problem caused by the ignition control module, such as misfiring or weak sparks, it will turn on the check engine light to alert the driver of the issue.

A faulty ignition control module can also cause other issues, such as stalling or a rough idle, which can also trigger the check engine light. 

6. Car Won’t Start

If the ignition control module fails completely, the car may not start at all.

The ignition control module is responsible for triggering the ignition coils to produce a spark that ignites the fuel-air mixture in the engine’s cylinders. If the module is not functioning correctly, it can cause a badly timed spark or no spark at all, which can prevent the engine from starting.

Additionally, a faulty ignition control module can cause other issues with the ignition system, such as intermittent stalling, which can also prevent the engine from starting. 

If the ignition module is faulty the engine may not crank or it may crank but not start. This is because a complete failure of the ignition module may cause a weak spark that is not strong enough to ignite the fuel in the engine and to keep it running after the starter motor disengages.

Causes of a Bad Ignition Control Module

The most common cause of a bad ignition control module is age and exposure to engine heat over a prolonged timespan. The module’s internal components can eventually become damaged due to exposure to high temperatures, which will cause the module to fail.

Other causes of a bad ignition control module include faulty ignition coils, a worn-out distributor, and electrical issues such as loose or corroded connections.

Exposure to moisture or other contaminants can also cause the module to fail. Regular maintenance and inspection of the various parts of the ignition system can help prevent issues with the ignition control module in the long run.

1. Age and Wear

One of the most common causes of a bad ignition control module is age and wear. Over time, the module can become damaged due to exposure to heat, vibration, and other environmental factors. This wear and tear can cause the module to malfunction, leading to engine performance issues.

As the module ages, its internal components can also wear out, causing it to fail. This can result in a variety of symptoms, including misfiring, stalling, and difficulty starting the engine.

2. Environmental Factors

The environment in which the vehicle is operated can also contribute to the failure of the ignition control module. Exposure to extreme weather temperatures, moisture, and corrosive substances can all cause damage to the module over time.

If the vehicle is frequently operated in a hot and humid climate, the high levels of moisture in the air can corrode the module’s internal components. This corrosion can cause the module to malfunction, leading to engine performance issues.

3. Electrical Overload

The ignition control module is an electronic component that is sensitive to voltage spikes and electrical surges. If the electrical system experiences a sudden increase in voltage, such as from a faulty alternator or battery, it can cause an overload that can damage the module’s internal components.

Additionally, a short circuit or another electrical issue in the ignition system can also cause an electrical overload that can damage the module. For example, when an ignition coil fails, it can produce a high-voltage spike that can damage the ignition control module.

4. Manufacturing Defects

In some cases, a bad ignition control module can be the result of a manufacturing defect. If the module was not manufactured to the proper standards, it may be more prone to failure than a properly manufactured module.

Manufacturing defects can manifest in a variety of ways. For example, the module may have a weak solder joint or a faulty component that causes it to fail prematurely. These defects can cause the module to malfunction, leading to engine performance issues.

What Next – Diagnosing a Bad Ignition Control Module

If your car is exhibiting symptoms of a bad ignition control module such as engine misfires, stalling, not starting easily or if the check engine light is on, then the first thing to do is to run an engine diagnostic to see if there are any error codes that point to the ignition control module.

P1351 is a manufacturer-specific diagnostic trouble code that is defined as “Ignition Control Module Circuit Voltage High” or “Ignition Control Module Circuit Voltage Out Of Range.” This code is set when the powertrain control module detects an abnormal voltage in the control circuit of the ICM (Ignition Control Module). 

Several other engine error codes are related to a bad ignition control module. These codes are typically associated with engine misfiring, which is a common symptom of a faulty ignition control module. Some of the most common engine error codes related to a bad ignition control module include:

  • P0300: Random/Multiple Cylinder Misfire Detected
  • P0301-P0312: Cylinder 1-12 Misfire Detected
  • P0351-P0358: Ignition Coil A-H Primary/Secondary Circuit Malfunction
  • P1336: Crankshaft Position Sensor Variation Not Learned

1. Visual Inspection

If there are engine error codes related to the ignition system then one of the first steps in diagnosing a bad ignition control module is to perform a visual inspection.

The location of the ignition control module can vary depending on the make and model of the vehicle. In some vehicles, the ICM is located within the distributor, while in others, it may be mounted on the firewall, fender, or other locations within the engine compartment. To determine the exact location of the module in your specific vehicle, it is best to consult the vehicle’s owner’s manual or a repair manual for your make and model.

Once located, look for any signs of damage, such as cracks, corrosion, or burn marks. Check the wiring harness and connectors for any signs of damage, such as frayed wires or loose connections. If everything looks good, move on to the next step.

2. Using a Multimeter

Using a multimeter is a common method for testing the ignition control module. Start by disconnecting the wiring harness from the ignition control module. Set the multimeter to the ohms setting and connect the positive lead to the B+ terminal and the negative lead to the ground terminal. The multimeter should read between 0.1 and 3.0 ohms. If the reading is outside of this range, the ignition control module may be faulty.

Next, set the multimeter to the volts setting and connect the positive lead to the ICM terminal and the negative lead to the ground terminal. Have an assistant crank the engine and observe the voltage reading. If the voltage reading is less than 0.5 volts, the ignition control module may be faulty.

3. Using an Oscilloscope

Using an oscilloscope is another method for testing the ignition control module. Connect the oscilloscope to the ICM signal wire and the ground wire. Have an assistant crank the engine and observe the waveform on the oscilloscope. The waveform should be a square wave with a frequency of approximately 120 Hz. If the waveform is not present or is distorted, the ignition control module may be faulty.

It is important to note that these tests are not definitive and should be used in conjunction with other diagnostic methods. If you are unsure about how to perform these tests or interpret the results, consult a qualified mechanic or refer to the vehicle’s service manual.

About the author

The Motor Guy

The Motor Guy is a passionate car enthusiast with a love for troubleshooting and diagnosing all sorts of vehicle problems.

With years of experience in OBD diagnostics, he has become an expert in identifying and solving complex automotive issues.

Through TheMotorGuy.com, he shares his knowledge and expertise with others, providing valuable insights and tips on how to keep your vehicle running smoothly.

Qualifications:
- 12 years experience in the automotive industry
- ASE Master Automobile Technician
- A Series: Automobile and Light Truck Certification, A9 Light Vehicle Diesel Engine Certification
- Bachelor's Degree in Information Systems