I just ran my 0-360 which the D-180 is mated with and this SLN code flashes in red on the #4 cyl. Checked all connections firewall forward, swapped the #2 & #4 leads with no change. I cannot find this code anywhere.Also reads normal ambient temp comparable to other cyls. when engine is not running..... What's up? Anyone ever seen this or know what it is trying to tell me? This was the first run of this engine in 9 years. Even with the red flashing code it was a great day. T-18 will fly soon.