8904

Possible Causes

• •UEGO internal supply voltage is low
• •Power is noisy due to a failed alternator
• •Supply voltage problem
• •ECM is unable to monitor the noise via the low-passed supply feedback
• •UEGO processing circuitry supply voltage is too low for normal operation (while Vbat or Vrelay low-pass filtered voltage is > 9.0V)
• •Noisy power due to a failed alternator
• •ECM is unable to monitor noise via low-passed supply feedback

Suggested Actions

1. 1Replace ECM and re-test
2. 2Inspect alternator and repair/replace as needed
3. 3Troubleshoot supply voltage source; repair/replace as needed
4. 4Replace UEGO sensor and re-test

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