Diagnostic Aids

If the engine has been allowed to cool overnight to an ambient temperature, both coolant and MAT temperature may be checked with a Scan tester. The readings should be approximately the same. A Code 23 will result if circuits No. 472 or 452 are open. If Code 23 is intermittent, see INTERMITTENTS in TESTS W/O CODES article.

Fig 1: Circuit Diagram Chart Code 23

Courtesy of GENERAL MOTORS CORP.

Fig 2: Flow Chart Code 23

Courtesy of GENERAL MOTORS CORP.