Quickly tell ECU trouble, ECU alternative method Notes!

With the development of electronic technology,more and more electronic products are applied to cars.ECU(Electronic Control Unit) is one of the most important component.ECU is the same as CPU which is the same as the ordinary computer, by the microprocessor (CPU), memory (ROM / RAM), input / output interface (I / O), analog-digital converter (A / D) and plastic surgery, drive large scale integrated circuit composition.In a word,ECU is the brain of car.


Due to complex structure, high technology content, ECU become valuable part of the car, although ECU usually low failure rate, but general maintenance staff is difficult to judge if ECU fault. Currently ECU fault diagnosis has become a restricted area for many repairman.


Today I share a shortcut to judge the ECU fault–The Alternative Test Method. If conditions permit, the alternative test method is a shortcut to judge the fault, but when use alternative method to determine whether the ECU is faulty there are a lot of attention.


Alternative Test Method principle: Use a reliable component to replace a component (or circuit) which need to be checked, if the replacement is working properly, indicating the components to be investigated is faulty. If the failure phenomenon after replacement does not change, you can rule out the possibility of failure to be examined components, further narrow the scope of the fault.

Firstly,you need same ECU,include model,software version.


Alternative Test Method advantage: Alternative method for a variety of fault diagnosis, but should be targeted when used, this will save the diagnostic time, improve the success rate of diagnosis. In the use of alternative methods to check the ECU process, should also note the following points:


  1. You need same ECU,include model,software version.

2.After replace ECU,some car need to adjust or program ECU; Most manufacturers regulate that ECU can be programmed only 3 to 7 times.Otherwise it will cause the ECU update failure. In a period of time After ECU replaced, it needs to adjust learning automatically. The relative parameters stored previously will lose. So after replacing new ECU, if the car still fails to start, don’t judge blindly ECU is damaged or not.


  1. In a special situations, a fault is caused by two or more points of failure.At this time if just replace one components,the symptoms may still remain.You must also replace two or more components to be tested until the failure phenomenon disappear.And then try to replace the original component one by one, then try to judge the fault position by combining with the accompanying phenomenon.


  1. Alternative method is more effective for the single component which has fault situation. Usually, the method can be mosteffective after diagnose the specific direction and scope by other means. If replace blindly, it may cause secondary damage to the circuit board and components.


5.ECU which has integrated circuit multi- pin component, using alternative should more carefully. Usually, carry out the diagnosis only after the clear conclusion is made. Repairmen should have relevant knowledge about the computer, electronic circuits and electronic components. Also, they need excellent welding skills. In general, weld out directly the electronic components which are suspected, and then replace them with the electronic components which have the same model. General electronic components are very cheap in electronic stores. But pay attention to their quality, such as electrolysis capacitor must choose tantalum, silver electrolytic capacitor, and require capacitors with high precision. Meanwhile, during the replacement, welding work must be carried out only when the electricity is cut off.


In general, the control computer of electronic-controlled engine, ECU is rarely damaged. Alternative method just helps to determine ECU damages roughly. Once ECU damages are judged, must determine clearly the causes of damage. According to experience, as for ECU damages, should focus on the stability of the power supply circuits and power supply voltage. Also, pay attention that whether the power supply circuits have poor contact, whether the oxidation and corrosion happen, and so on. If fail to find out the damage causes and just replace the ECU simply after determine the ECU faults, ECU may damage again and again, it may cause unnecessary losses.

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