How To Diagnose Your Car’s Engine Control ModuleMintt
The Powertrain Control Module (PCM) is also known as the Engine Control Module (Engine Computer Module), and it is the main on-board computer that monitors/controls vehicle functions. The PCM is available in nearly all modern vehicles as a single computer. Older cars have the Engine Control Module and the Transmission Control Module (TCM) monitoring engine and transmission functions, respectively. At its worst, a failing PCM might render your car inoperable.
Reasons the PCM fails
Powertrain Control Modules often fail because of voltage overloads or natural environmental factors. Voltage overloads that affect the PCM often result from short circuits in the actuator circuit. A short solenoid can also lead to the damaging of the PCM. If such a solenoid isn’t found, there are high chances that it would damage the replacement PCM.
Environmental factors such as exposure to moisture or water can result in the corrosion of the PCM. Water causes serious harm to the PCM since it shorts the components circuits beyond repair. Vibration and thermal stress can also damage the PCM, and this will take a toll on a car’s performance. Prolonged exposure to thermal stress and vibration result in the formation of microcracks on the PCM’s motherboard and circuitry systems.
Replacing your car’s PCM can cost significantly lower if your warranty hasn’t expired. But unlike other vehicle components, the PCM is relatively expensive. You should, therefore, rely on the services of a reputable or experienced mechanic to inspect your car and perform a diagnosis of its systems before replacing your car’s PCM.
Testing the powertrain control module requires sophisticated tools and simulators and this means that the PCM has to be sent back to the manufacturer hence the no return policy on PCMs.
How to test a PCM
You can start testing your car’s PCM by conducting a visual inspection and this necessitates the checking for disconnected wires or corrosion. Also ensure that the PCM is connected to the battery. Remember to fully charge your car’s battery since low voltages deprive the PCM’s sensors sufficient power leading to their malfunction. If a PCM is not affected by corrosion and all the cables are plugged in place, then you should find an OBD II scanner that you will connect to the PCM. The OBD II scanner will retrieve trouble codes from the PCM. These error codes are helpful as they will help get to the root of your car’s problems. The OBD II scanner is easy to use, and it will reduce the time you spend on PCM diagnostics.
Symptoms of A Failing PCM
You need to have your PCM checked if your car is showing inconsistent performance or if its onboard systems are malfunctioning. The PCM monitors and controls your car’s essential functionalities, and it can affect the car’s operations leading to an undesirable driving experience if it has issues. The following five signs show an ECM is failing:
1. Illuminated Check Engine Light
The check engine light allows you to know when your engine is having problems that need immediate attention. A bad PCM can make the check engine light to illuminate and stay on since the PCM controls the functioning of the check engine light. A failing PCM can also result in the displaying of the wrong error codes that show that functional components need attention.
2. Car Starting Problems
PCM problems can lead to troubles when you are starting your car since the engine needs computer input during ignition. A failing PCM can affect the Engine Control Module, and this may in turn prevent your car from starting on the first attempt. Keep in mind that there are other reasons your car might not be starting during ignition.
3. Poor Fuel Efficiency
Fuel efficiency is always a concern because car owners want to cover more miles on less fuel. The PCM regulates fuel to air combustion ratio and also regulates fuel injection into the engine. Failing ECMs can lead to the inefficient use of fuel, and this happens when excess fuel is injected into the engine for combustion. Poor fuel efficiency lowers gas mileage and poses environmental risks due to excess carbon emissions.
4. Erratic Engine Performance
Your PCM might be having problems if you notice poor engine performance. A drop in your car’s handling or maneuverability might also be an indication of a PCM problem since the PCM controls onboard systems that regulate vital engine and transmission functions. A Transmission Control Module malfunction can result in the untimely or random shifting, thus the erratic engine performance.
5. Failure of Emission Tests
Failing emission tests is a sign that your car needs a PCM replacement. As earlier mentioned, the PCM controls how much fuel is injected into the engine and the fuel to air combustion ratio. After you replace your PCM, you can retake your state’s emission tests without the fear of failing. The replacement PCM should solve your car’s emission problems.
How Do You Know if Your PCM Is Bad?
The simplest way to determine if your PCM is bad is looking out for error codes / stall or misfire for components that are working fine or an illuminated check engine light that doesn’t turn off.
How Do You Check PCM Voltage?
Connect a multimeter to the right PCM connector after setting it to the highest voltage. A reading of zero is an indication of a bad or failed PCM.
How Do You Reset the PCM?
Disconnect the car battery terminals then reconnect them after five minutes; this resets the PCM.
What is A Bad PCM?
A bad PCM is a PCM that malfunctions, fail, or doesn’t work as designed.