intermittent spn 0102 fmi 18 cm871

[Rawze]

(09-04-2026 )jgriffin812 Wrote:  ... hit my regen rocker switch...

== (older engines 871,2250,2350's) the "Parked Regen" switch is completely ignored by the ECM unless it is already asking for a parked regen. On some of the newer trucks, this switch can also trigger what's referred to as a rolling psudo-regen (where the engine revs up slightly every time you get to to a traffic light), as a sort of "stay-warm" feature to keep the system hot, but only if it is in need of a 'rolling regen'. The psudo-regen will cancel though if you are sitting for very long, as it can only do a rolling regen effectively while your pressing the fuel pedal hard and driving down the roads under engine loads to keep the temps up.

== The "Regen Inhibit" switch prevents any type of regen (automatic or otherwise) when active. This switch is
essentially a switch to tell the ecm that "you parked in tall grass and it can catch fire" switch... preventing fuel from going into the exhaust system.

== The HET (High exhaust Temp) lamp in the dash is simply an indicator (that can come on when you drive below a certain speed) as a warning for you to NOT park in tall grass, as the exhaust piping is above a certain temperature. It has nothing much whatsoever to do with regen system, is independent, etc.

[jgriffin812]

When I push the parked regen switch up to start a parked regen, the truck, when it want it, the truck will raise rpms and act like its doing a regen but it most of the time doesn't get hot enough to turn the hot exhaust light, HET, on. She goes up to about 1200 rpm for a while then drops to around 1000 rpm before it gives up. with egt temps at cylinder 5 in the 400 to 450 maybe often lower. My understanding was the hot exhaust light would come on every time it would regen.

[Rawze]

(09-06-2026 )jgriffin812 Wrote:  When I push the parked regen switch up to start a parked regen, the truck, when it want it, the truck will raise rpms and act like its doing a regen but it most of the time doesn't get hot enough to turn the hot exhaust light, HET, on. She goes up to about 1200 rpm for a while then drops to around 1000 rpm before it gives up. with egt temps at cylinder 5 in the 400 to 450 maybe often lower. My understanding was the hot exhaust light would come on every time it would regen.

there is no such thing as a 'regen light' in an ISX ...

read my post above.