Diagnostic Trouble Code (DTC) Output Format Description

The EEC system communicates service information by way of self test service codes. These service codes are two digit numbers representing self test results. Service codes are transmitted on the Self Test Output (STO) wire on the vehicle self test connector. Service codes are in the form of timed pulses, read by the technician on a scan tool, analog voltmeter, or MIL.

Code Cycle Break:

CODE CYCLE BREAK
The time between code cycles is 4.0 seconds (time the light is off).

First Digit Of Service Code (Tens Position) During One Cycle:

FIRST DIGIT OF SERVICE CODE (TENS POSITION) DURING ONE CYCLE
Digits in the tens position of the warning code represents the number of times the light is on 1.2 seconds during one cycle. Note that the light goes off for 1.6 seconds between long and short pulses.

Second Digit Of Service Code (Ones Position) During One Cycle:

SECOND DIGIT OF SERVICE CODE (ONES POSITION)
Digit in the ones position of the warning code represents the number of times the light is on 0.4 seconds during one cycle.