Pretest Inspection-TBI: Notes

Before testing TBI components, perform basic engine checks (ignition system malfunctions, incorrect engine adjustments, etc.). See BASIC TESTING article. Perform TBI diagnosis only after conventional components have been inspected.

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 (Code No. 4 not used in this application). See the DIAGNOSTIC CODES-TBI  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 second to display codes. After indication of zero volts for 2 seconds, the next code (if any) will be indicated.

System malfunctions encountered are identified as either hard failures or intermittent failures as determined by the ECU.