As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TUS- FLIGHT 4172 DURING TAXI, DURING FLIGHT CONTROL CHECK, "IB FLT SPLRS" AND "IB SPOILERONS" CAUTION MSGS APPEARED. RETURNED TO THE GATE. REPLACED LT IB MFS PCU IAW CRJ700 AMM 27-62-01-000-801-A01/400-801-A01. OPS AND LEAK CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.