Troubleshooting a 1989 Chevrolet S10's engines can be a complicated task. The engine itself has many hard to reach spots, and since every symptom can have multiple causes, the process can be time consuming. There is a way to streamline the process. Even though S10 predates 1996 and the contemporary On-Board Diagnostic system, you get troubleshooting leads from the truck's computer. To do this, you will need to put the S10 into a self testing mode and count how many time the check engine light flashes at you.
Locate the Assembly Line Diagnostic Link. The ALDL outlet will be below the S10's steering wheel.
Straighten out a paper clip and then bend it into the form of a long "U." Place the ends of the paper clip into the "B" and "A" slots on the ALDL. These slots are next to each other, and are at the far right end of the ALDL's top row.
Insert the key into the S10's ignition and turn to "On." Leave the engine off.
Count how many times the check engine light flashes. Chevrolet's flash codes consist of a first and second number. The first is represented by a long flash, and the second is represented by a shorter flash. For example, code 55 will be five long flashes and five short flashes. There will be a pause to signify the end of a code and a beginning of a new one. Ignore code 12 once the flashing starts. It is always the first one relayed. Write the codes down as you count them.
Turn the S10's electrical system off and remove the paper clip from the ALDL.
Consult either a Haynes Repair Manual or locate the old Chevrolet flash codes online (see Resources). Read the definitions and make a list. Group the codes in clusters by where they will be located in the engine.
Open the S10's hood and begin troubleshooting the engine with your list of problems.
