Initial Inspection and Diagnostic Overview

Fig. 5 ECU connector terminal location.:

Fig. 6 ECU connector terminal location.:

Before performing system diagnosis, ensure engine and all related systems are in proper operating condition.
The feedback carburetor system can be diagnosed using FBC checker 09341-21000 and harness connector 09391-21100, Fig. 4. If checker is not available, a suitable digital-type voltmeter may be used. If using a DVOM, carefully backprobe the FBC connectors. The following procedure will cover the DVOM test only.

1. Turn ignition switch to Off.
2. Backprobe harness connectors ``A'' and ``B'' from ECU, Figs. 5 and 6. as necessary.
3. Check voltage of each terminal, Pinout Values and Diagnostic Parameters
4. If voltage readings are not as specified, check corresponding sensor and related electrical wiring and repair or replace as necessary.
5. After repair or replacement, recheck voltage reading to confirm component is performing well.
6. If system diagnosis reveals all components are operating properly, replace ECU.