^Cleaned MAF sensor and electrical contacts on the transponder antenna on the steering column. After 90 miles, the P1171 code has not returned and the car has not failed to start. The ETC light has come back on.

My 2000 V70 XC (138k) has the same issue as the original poster. It also throws a P1171 code and the ETC light comes on. I purchased the car used and the dealer said he had replaced the "Throttle Body" which I took to mean the ETM. The problem started after I changed the oil and replaced the spark ...