Testing & Diagnosis: Diagnosis
The diagnostic system, which monitors all input signals from each sensor, is an integral part of the ECU. If an abnormal input signal occurs, that item is memorized by the ECU. There are 6 diagnostic codes which can be confirmed using a voltmeter. See DIAGNOSTIC CODES table.
If 2 or more systems are non-functional, they are indicated in order of increasing code number. Indication is made by deflection of voltmeter pointer. A constant 12 volts indicates system is normal. If system is abnormal, voltmeter will alternate between 0-12 volts every .4 seconds to display codes. After indication of zero volts for 2 seconds, the higher code is indicated. See Fig 1 .
NOTE:
ECU abnormal diagnostic memory is kept by direct power from battery. Memory is not erased by turning ignition off, but will be erased if battery or ECU is disconnected.