- Description of On-Board Diagnostics

When a problem develops in the C-3 system, the Check Engine or Service Engine Soon light will come on and a trouble code will be set in ECM memory.

INTERMITTENT PROBLEMS
If the problem is intermittent, the Check Engine light will go out after approximately 10 seconds when the problem clears up.

CLEARING CODES
The trouble code will be stored in ECM memory until voltage to ECM terminal ``R'' is removed for approximately 10 seconds.

This can usually be accomplished by removing the ECM fuse located in the fuse block.

ENGINE RUNNING/CHECK ENGINE LIGHT OFF CODES
If a trouble code can be obtained when the Check Engine light is off and the engine is running, a determination should be made to see if the problem is intermittent or if the engine must be at certain operating conditions to turn the Check Engine light on.

For instance, trouble codes 13, 24, 44, and 45 require engine operation at part throttle for at least 5 minutes before the Check Engine light will come on.

Likewise, a problem indicated by a trouble code 15 requires 10 minutes of engine operation before the Check Engine light will come on.