Owner manual

2-5 GM

NOTE:

It may be necessary to test drive the vehicle to

reset "hard" fault codes 13, 15, 24, 44, 45, and 55

after they have been erased.

■ If "Service Engine Soon" light does not turn on, the initial

stored fault codes were all "intermittent" fault codes.

(Refer to the "Diagnostic Procedures" section in the

manufacturer's service manual for your vehicle.)

8. Follow the testing and repair procedures outlined in the

manufacturer's service manual for your vehicle to correct

"hard" faults. Codes should be addressed and eliminated

in the order they were received, erasing and retesting

after each repair is made to be sure the fault was

eliminated. Code 12 will appear alone when no other fault

codes are present.

NOTE:

Whenever codes 51, 52, 54, or 55 are displayed with

other codes, troubleshoot and eliminate the "50

Series" codes first, then proceed with the lower-

numbered codes.

9. Turn off ignition and remove the Code Reader.

2.3.1 Servicing Fault Codes

Diagnostic trouble codes indicate a problem in a circuit, not

necessarily a faulty component. DO NOT replace components

based only on trouble codes without first following the service

procedures described in your vehicle's repair manual. Most

faults (including those that set trouble codes) are caused by

damaged, shorted or open wiring, damaged or corroded

connections, improper voltages or grounds, or other

mechanical problems.

Sometimes a fault in one circuit or system will cause the

computer to set a fault code for a different circuit or system.

Example:

A defective spark plug wire can cause a "rich condition" fault

code to be set on the oxygen sensor circuit. In this case,

replacing any component in the oxygen sensor circuit will not

correct the fault, because the problem is caused by the

defective spark plug wire and not by the oxygen sensor circuit.

This is called a "false" code.

For this reason, it is

IMPORTANT that you make a thorough

inspection of all systems: wiring, hoses, vacuum, engine

mechanical, charging, ignition, power, ground, fuel, (some of

these systems are not connected to the computer system, but