DTC 25

Codes 25 & 53 Diagnostic Chart:

CHECK CIRCUITS

Check Circuits:

NOTE: Normal operation of the vacuum switching valve system, including the ECM, is indicated if the valve functions properly when the ignition switch is turned "ON" (engine not running) with the diagnostic lead connected.

Code 25 indicates output terminal shorted or open circuit.
Code 53 indicates defective ECM driver transistor or grounding system.