Reading Codes
All trouble codes are 2-digit numbers. PCM outputs codes one digit at a time. These codes indicate current faults in system and should be serviced in order of appearance. See TROUBLE CODE REFERENCE under CIRCUIT TESTS to find correct CIRCUIT TEST.
Scan tester, if used, will count pulses and display them as a digital code. If using MIL, trouble codes are displayed as light pulses from CHECK ENGINE light. When using MIL, pay attention to length of pauses in order codes correctly. See Fig 1 . Pass Codes
Code 55 indicates system passes that portion of test. If Code 55 is not retrieved, proceed to CIRCUIT TEST corresponding with trouble code that is output.