58 Battery Voltage Unstable

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The PCM monitors ignition voltage on CKT. 439 when powered up. The purpose of flag 58 is to detect an unstable ignition voltage to the PCM/EC.

Information FLag Parameters

Information Flag 54 will set if:

  • Battery voltage changes more than three volts instantaneously.

Diagnostic Aids

  • When attempting to diagnose an intermittent problem, use the Scan Tool to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem. Select MALF History from Scan Tool EC menu.
  • Wiggle the PCM connector. Watch Scan Tool to see if battery voltage reading changes sharply.
  • Check PCM connector. Check the tightness of the female terminal grip with a spare male terminal.
  • Wiggle and tug the harness at the ignition switch. Watch Scan Tool to see if battery voltage changes sharply. Lightly tap the PCM. Watch for changes in the CTS reading

NOTICE: Information flags should be used for diagnostic purposes only. They do not necessarily indicate component malfunction/failure.