How to test Ecu with a Multimeter in few steps- Meterreviews

ECU or engine control unit is quite similar to CPU of a computer, or in simple words, we can say it the brain of a vehicle. A faulty ecu can create a number of problems in your car like a sudden engine failure, alternator failure, difficulty in engine starting or poor engine performance. To check ecu for diagnosing issues with a vehicle we’ll teach you “how to test ecu with multimeter? “.

The ECU is an important component of the vehicle and it should be checked regularly for any faults. Also, keep one thing in mind that every type of car engine issue isn’t due to ECU problems, there are maybe other sensor or wiring issues. So before testing ecu you should first guarantee that all other sensors and circuits were properly checked and found ok. After that follow these simple steps written below to check ecu condition.

ecm inputs

Initial setup for testing Ecu

  • First of all check vehicle’s battery whether it’s giving enough voltage to car circuits. Wear gloves and other safety equipment to avoid any type of loss during troubleshooting.
  • Now is the time to set multimeter for this test, connect meter black lead to COM jack and red one to jack with volt, amps and ohms indication. Also turn multimeter’s wheel selector to current checking point.
  • Before conducting this test first observe ecu physically, check if all connections, wires and plugs are intact and there is no visible damage found in ecu and its surrounding elements.
  • Make sure that ecu is in contact with other electric circuits and energized energized through battery.

Testing Ecu with Multimeter in 8 steps

  • Before testing ecu directly you should check its fuse and relay first, if you don’t know about exact location of fuses and relay you can take help of an automotive technician or see video below.
  • Our aim is to find a path from ecu to battery ground in order to check whether load is in feasible range.
  • For checking ecu with multimeter connect meter positive lead to battery ground point and negative lead to powertrain control module’s connector for a very short time in order to protect the component being tested.
  • Make sure that pcm or ecu is getting valid power through battery.
  • Now turn on ignition key and check if ecu or ecm(engine control module) component you are testing is supplying power?
  • If yess then connect negative lead of multimeter to positive terminal of battery and check amps.
  • In this condition while vehicle ignition key is on, every other type of load is off meter should record a reading of 1 A to 1.2 amps.
  • A reading which is significantly above then 1.2 amps may be a sign of some problem with your vehicle’s ecu.
  • If you can’t understand the procedure, don’t try it yourself either consult with some professional automotive man.
how to test ecu with multimeter

How to test ecm sensors with Multimeter

Ecm is an abbreviation or engine power train control module, we can also say it ecu( engine control unit). It has a number of sensors, drivers, and other equipment to control and give instructions to different equipment of a vehicle. In following easy steps we’ll guide you to test ecu sensors with help of a digital multimeter.

Coolant sensor

  • Set multimeter on required settings, check meter battery and leads condition.
  • Now for testing coolant sensors, first you have to locate exact position of sensor. For this you may take help from car manual or circuit diagram.
  • Now connect meter leads with both ends of coolant sensor while setting meter at ohms, it should give reading from 1900 ohms to 2100 ohm or higher.
  • If you get this reading then sensor is fine otherwise do more troubleshooting.

Crankshaft sensor

  • For testing cranshaft position sensor with multimeter attact meter leads to sensor points and record ohm reading.
  • Now take some metal piece and pass it near to sensor position, while you doing it resistance reading on meter should change according to position of that metal piece.
  • If readings are changing with change in metal position that will be a sign of correct sensor performance.

Mass flow sensor

  • For testing mass flow sensor with multimeter try to find it in incoming air duct. After that inspect sensor phyically for wear and tear or any sign or burning/ breakage.
  • After getting sured that sensor is receiving 12v or more power supply from battery, remove sensor and set your meter to ohms range.
  • Connect one of multimeter’s lead to mass flow sensor’s signal point and other to the ground.
  • Multimeter should get a reading near to or equal to zero ohms. If you get an infinite ohm value, that will be a clear indication of sensor failure.

Common Symptoms of a Bad Ecu

There are many symptoms that can tell you about a faulty or bad ECU earlier, try to focus on those symptoms and get your ecu examined regularly. Remember many engine issues have the same type of symptoms, so by one symptom, we can’t conclude about results. Here is a list of some most common symptoms of a bad ecu,

  1. “Check engine” indication of car screen even after resetting.
  2. Engine instantly stops during normal ride with no clear reason.
  3. Memory check error of control module.
  4. Issues of fuel injetor pulse.
  5. Broken pins in ecu.
  6. Occasional starting problems.
  7. Poor fuel economy.
  8. Random engine stalling.
Other method to test ecu with a multimeter.


Testing ECU with a multimeter could be a tricky and time taking process for newbies or people having no automotive experience. You can do it by simple multimeters, best multimeters for automotive use (check our list), and car diagnostic tools that have some pro features like obd scans and others by which even a blank person can test ecu with simple steps.

We’ll recommend you to be careful while doing these types of tests for wellbeing of both your and your vehicle’s expensive equipment which may cost hundreds of bucks. If you still failed to understand this guide you should watch video given above with another method to check ecu and follow it.