The ECU stores information about all detected malfunctions in the memory of the self-diagnosis system until it is erased.
When the ignition is switched on, the injection system malfunction indicator lamp comes on and goes out as soon as the engine starts. If the lamp does not go out or lights up when the engine is running, this indicates a malfunction of the computer.
The exact determination of the malfunction is possible when connected to the diagnostic block in the engine compartment of the KM-640 diagnostic tool from General Motors. Each malfunction corresponds to a two-digit light code, consisting of a certain number of flashes of the malfunction indicator lamp. Flashes corresponding to the first digit are read first (for example, number 1 - one flash, number 2 - two flashes, etc.), followed by a short pause; then flashes are read, indicating the second digit, then a long pause, indicating the end of the code.
Set the device switch to position «IN», turn on the ignition. At the same time, the control lamp shows the code «12», indicating the start of self-diagnosis. The ECU-latched fault code is then displayed, after which it jumps to the next fault code if more than one fault is detected at the same time. After displaying all fixed fault codes, the fault display cycle is repeated twice. As the fault codes are displayed, write down and then determine the fault according to the table below.
To erase fault codes from the ECU memory, turn off the ignition and disconnect the wire from the negative terminal of the battery for at least 1 minute. In this case, you should pay attention to the fact that the memory of other electronic devices in the car, such as a radio receiver, may be erased.
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