Fault Code Lookup

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9
Open Inducer Limit Error
This code typically points to
  • Open inducer limit

Next checks to confirm
  1. Check inducer limit
  2. Inducer retry behavior documented in abnormal-condition section

Escalation
Heating fault; stage fallback/retry behavior documented separately
Reset behavior
Clears when inducer limit condition clears.
Urgent
Fix now
Cross-generation conflict
Code 9 means completely different things across Trane/American Standard legacy platforms. On UD2/DD2 and UC1/DC1, it's an ignitor/grounding fault. On AUY/TUY and AUH2/TUH2, it's an open inducer limit — totally different diagnostic path. Your model prefix determines which it is.
Source
Trane 18-CD26D1-13 Installer's Guide, p.42-43