ECU is programmed to detect ignition problems.
Checking for trouble codes can speed up your diagnosis.
If ECU detects a problem a diagnostic code will be set in memory

Verify "CHECK ENGINE" light circuit is operational.
Ensure battery voltage is above 11 volts and charging system is okay.
Engine must be at normal operating temperature.
Transmission/transaxle must be in Neutral or Park.
Air conditioner and other accessories must be off.
Throttle valve must be closed (throttle position idle contacts closed).
Turn ignition switch to "ON" position with engine off.
Place jumper wire across "TE1" (or "T") and "E1" terminals in engine check connector.
Count number of flashes from "CHECK ENGINE" light.
If system is operating properly (with no codes), "CHECK ENGINE" light will blink continuously and evenly.
NOTE:If "CHECK ENGINE" light stays on and will not blink codes, verify battery voltage is present at "TE1" (or "T") with key on and engine off.
Ensure "E1" has continuity to ground or self-diagnostics will not work.
If ground ("E1") is open, jumper "TE1" (or "T") to battery ground.

A trouble code will be identified by a .5 second flash on and off for the first number.
A 1.5 second pause will occur followed by the second number.
If more than one code is stored, a 2.5 second pause will occur before second code is flashed.
Once all codes have been displayed, a 4.5 second pause will occur and code(s) will repeat.
Trouble codes are given from smallest number code to largest number code.
After codes are retrieved, remove jumper wire to exit diagnostic mode

Answered by BMRFIXIT (expert)
19,733 answers provided