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: Code 23, Circuit Wiring Diagram & Flow Chart

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