How does an ECU (Electronic Engine Control Unit Computer) fail the Bench Test?

I will explain to you in this video what's is a ECU bench test, how we bench test, how do we determine if a computer failed the test and what it means if a computer failed the bench test. The steps in this video is just 1 method that we use to be able to diagnose computers test hundreds of different variety of DMEs.
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What is an ECU bench test?
ECU bench test is an aggregate simulation test carried out on ECU by mimicking the car conditions. It’s an examination of the ECU outside the car. The bench test determines the functionality of the ECU in the car. The ECU bench test equipment has LEDs light as an indicator for each car part or component on its panel. Those LEDs lights indicate if the ECU is active (or is in perfect working conditions) in those components.

How to carry out a bench test on ECU?
We fool the computer into believing it's connected to the vehicle.

We have the crankshaft and camshaft feeding the ECU signals (standard stuff).

Simultaneously we can diagnose if the main relay, check whether the fuel pump or engine light is working. If at any point we see on the bench any the LEDs light are not are getting activated, we automatically fail the computer on the bench test.

Secondly, we check if the injectors (we can measure/test up to 8 injectors simultaneously, depending on the numbers of the cylinder the car possess), and ignite coils are working.
In the situation, a customer complains his car is misfiring; what we will do first is simulate the ECU activities on the bench test. Check if the injector LEDs indicator lights are solid or blinking.
If they begin to blink, we can then replicate precisely the customer's complaint about the car on the bench.

We can deduce if the misfiring is caused either by the ignition coils, spark plugs, or injectors.
By just duplicating the issue, we can confirm to the customer that the computer failed the bench test. That's one way we can see this through this machine.

Thirdly, another thing we can check is the tachometer. Many computers have a tachometer bounce as you crank the car. If we don’t see it on the bench, then the computer has failed the bench test.

We can again simulate the computer (that is fooling it into thinking about what’s going on when it comes to the engine temperature by changing different signals).
The computer should act accordingly and if it doesn't act accordingly, by the way, triggering the checking green light or begins to fail or fade or stop. Then we can confirm its damage, and it has failed the bench test.

The fourth thing to do is to run a check with the oscilloscope to check the ECU's "heartbeat". If we see a signal different, either flat or overlapping, or which all deviates from the typical pattern, we say it fails the bench test.

Fifth, we do is check the power supply and power draw. Each computer has an ampere range (a certain amount of ampere it’s supposed to draw as its working. If we know the standard amp range is 1amps, but if we connected a computer connected and it draws too much above the amp range or draws fewer amps below the range. We know it’s not functioning correctly (which means it has failed the bench test).

We also have bench testing equipment to test distributors, spark plugs, and coil.
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What does it mean if a computer failed the bench test?
If we diagnose a computer to have failed the bench test, we don't know yet what is wrong inside the unit. We don't know if its cold solder joint, broken track, or if it is sulfur, we won't know until we go ahead and rebuild it

But bench test will let us know if there is an issue or not right away without having to spend too much time taking the components out and measuring or by carrying out in-depth forensics on the ECU.
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If you have any kind of Porsche, BMW or Ferrari that you're suspicious of the engine computer, give us a call. We love to be able to help you out with any issue or kind of questions you might have.
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Specialized ECU Repair
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