How to Diagnosis the ECU?

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Diagnosis of an ECU and peripherals:

The complexity of implementing all of this control, all of those inputs, and every one of those outputs requires relatively advanced self-diagnosis capability – traditional engine diagnosis becomes obsolete. The inputs and outputs of a European are individually monitored by the processor, often dozens of times a second, to confirm they’re within the tolerances set within the software. If a sensor reading falls outside of those tolerances for the pre-determined period, a fault is registered and a fault code is stored for retrieval by the technician.


Fault Codes:

When a fault code is stored within the memory, it always leads to a number of the logic within the software being bypassed with reduced engine efficiency, albeit with the engine still having the ability to function on a basic level. In some circumstances, the self-diagnosis routine discovers a significant fault that either fundamentally prevents the engine from running, or shuts the engine down within the interest of safety.

With modern engine management, the primary fault diagnosis step for a vehicle technician is to access fault codes from the ECU memory. These are often stored as 5 digit alphanumeric codes beginning with a P, B, C, or a U, followed by 4 numbers.

In addition to those codes, the technician may also view live sensor data through the diagnostic tool while the vehicle is running. This permits them to work out a sensor reading that’s incorrect, but not out of tolerance by enough of a margin to flag a fault code.

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