I have a US spec 348, Should my red slow down lights flash on startup. The yellow cel's do.
What do you mean by "flash"? They do come on during initial startup (bulb check), but should go out shortly thereafter.
my 5-8 flashed once when it was cold...it just flickered a few times on startup, but once there was just a little warmth, it went out. sjd
The slow-down lights should come on solid when the key is turned on and then slowly go out after a few seconds. The engine doesn't have to be running. If the lights flash or flicker when cold, there is a problem with the system. The early black potted slow-down light ecu's have close to 100% failure rate. The replacement green ecu's are better, but can still be the cause of the problem. The thermocouples that send the exhaust temperature signal can be bad as well. You can swap the 1-4 slow-down ecu with the 5-8 ecu, then if the problem moves with the ecu you know that it is defective. You should spend some time doing a proper diagnosis of the system (there are many threads on this subject if you do a search) if it is malfunctioning.
If the SDL bulbs are good and they don't come on for a few seconds at ignition "on", your exhaust ECU-s (TCU-s) might be bad (the black ones a certain to go bad, sooner or later). These TCU-s, when good, switch the SDL-s on for 2-3 sec. on every ignition "on" and this pulse also goes to the engine ECU-s to tell them "we are good". If you, in addition to no short light-up of the SDL(s), also get fault codes for TCU-s from the engine ECU-s, that confirms that the TCU-s are bad.
