checking car ecu with multimeter

Are you struggling with cold morning car starting problems until it warms up? Well, that’s not only you many peoples are having a problem with ECU. But you don’t need to worry about anything because In this article I will write on how do you diagnose it using a multimeter?

What is ECU on Car?

ECU stands for Engine Control Unit. It is commonly known as the engine control module. ECU has many functionalities like controlling a series of actuators on an internal combustion engine to enhance optimal engine performance, reading data from sensors, interpreting the data using performance maps, and adjusting the engine actuators. Other functionalities include

  1. Control ignition timing. engine control modules are fitted with variable valve timing. ECU will open this valve at a specific speed. At a higher speed, the valve will be open automatically than at a lower speed. Because of this function, more air will come to the cylinder, and fuel economy will be increased.
  2. Control of idle speed. This ECU functionality is present in a modern vehicle’s engines. The programmable throttle will control the Idle speed and cruise control functions. Also, the limitation of the speed monitoring will be done by ECU.
  3. Control air-fuel mixture.  In Modern, Engines ECUs use fuel injection to transfer fuel to the cylinders. The amount of fuel injected depends on sensor readings. The sensors will notify the ECU if the engine is running with too much fuel.

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Working of ECU?

Car ecu

Modern Engine Control Units used ECUs with microprocessors. The best thing about ECU is, it is made up of hardware and software components. The hardware of ECU’s has electronic fittings on a ceramic substrate and circuit board. The circuit board has a microcontroller or microprocessor that has the software. The software can be updated by reprogramming. By updating the code, the functionalities of the Engine Control Unit will be improved. Besides Engine Management, it will help in transmission control, anti-theft control, anti-skid brake control, and cruise control, etc.

What is a Multimeter?

A multimeter is a tool for measuring electrical quantities like resistance, voltage, and current. All these meters (ohmmeter, voltmeter, and ammeter) that measures those quantities are combined to a single meter is known as multimeters. There are two types of multimeters:

1. Analog Multimeters

Analog multimeters work on the principle of moving coil meters. These meters use the deflection of an indicator needle to indicate the level of the measurement on an analog display.

2. Digital Multimeters

 

How to test ECU with Multimeter?

There are five steps involved in  how to test a car computer system

Check for all the components of ECU, if they are properly fixed.

Take a multimeter and use the current breaker or fuse with one of the leads. This will increase the safety level of multimeter

Likewise, Test every component using your multimeter.

Also, Test the fuse and Relay first.

Find the setting that sits at 1 with probes apart then drops to 0 when they touch, or better yet the setting that beeps when you touch the tips if you have this feature! then got from each pin on the ECU to the relevant pins on the other end of the loom, this checks each wire for continuity

4 – knock sensor pin 1

5 – knock sensor pin 2

6 – brown/white – dizzy pin 1/- and throttle switch, and coolant temp sensor pin 2, and AFM pin 4

7 – knock sensor pin 3

8 – red/black – dizzy pin 3/+

9 – blue/white – AFM pin

10 – brown/green – coolant temp sensor pin 1

11 – red/blue – throttle switch

12 – brown/yellow – fuel rail pin 2

13 – brown – battery -ve

17 – blue/black – AFM pin 3

18 – green/white – dizzy pin 2/o

19 – brown/black – earth to head

21 – blue/red – AFM pin 2

22 – yellow -isv pin 1

23 – white – isv pin 3

25 – green – TCI pin 6

TCI unit:

1 – red/black – coil -ve

2 – brown/white – battery -ve

4 – black – coil +ve

6 – green – ECU pin 25

Then switch it to the voltage test mode put the negative probe on the battery negative then test these 2 pins:
1 – red/green – cranking live
14 – black/yellow – ignition live
While checking the overall condition of the wiring, look for black tape, dirty earth points, and check all the pins inside the plugs to ensure they’re not pushed back or bent. Don’t forget to peel the rubber boots back on the plugs to see the condition of the wires underneath.

How do you know if your ECU is bad?

Here are the most common symptoms of a bad ECU:

  • Check Engine Light stays on after resetting
  • Car was jump-started on reverse polarity
  • Engine turning off for no reason
  • Water Damage or Fire Damage on the ECU
  • The apparent loss of spark
  • The apparent loss of injection pulse or fuel pump
  • Intermittent starting problems
  • Overheating ECU
  • ECU has Broken Pins
  • Loss of communication between the ECU and the Scanner
  • A control module memory checksum error

After reading this article “How to test ECU with Multimeter? ” you will be able to check the ECU of your car. We have tried to cover each aspect of the ECU and will look for more and try to add those in the next update. Have you checked your car ECU? Let us know in the comments section below.

By inham

Inhamullah Jadoon is an Electrical Engineer and Founder of geekyengineers.com. He has huge experience in the field of Engineering and assisting Engineers in Software and Hardware issues.

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