2008 HR ISC - Sudden Dash Warning Light on - Can't Figure it Out -(SOLVED REGEN CYCLE)

[DaKevster]

New to me 2008 Hol Rambler 40PLQ with ISC360, Allison 3000. I just had a bunch of engine/chassis maint done; fluids, filters all changed. Have driven 150 miles since then with no issues. Today, was driving with no heavy load abt 15 mins and get this dash symbol. I have looked in the RV manuals, searched online, done reverse google image search, and I am coming up blank on what this means. There are the standard temp dial gauges on engine/trans that have the thermometer temp symbol. This is slightly different, with what looks like a blowing temp symbol. At the time trans temp was 161 and engine temp was 177 and gauges were all in the middle. Air pressures were fine. I'm stumped. Went abt 5 miles with that lit up and all seemed normal. Haven't tried starting/driving it since. Anyone know what this means or where to look up info?

 

[DavidL]

https://dtnacontent-dtna.prd.freightliner.com/content/public/dtna-servicelit/dtna/en_us/thomas-built-buses/drivers-manuals/saf-t-liner-c2-school-bus-drivers-manual/section_ch06dm466.html

 

Looks like number 5:  High Exhaust Temp

[Ivan K]

It is a regeneration indicator. Doesn't mean anything wrong, it is to burn out the particulate filter since you have DPF and should be done while driving, your exhaust will get very hot during that time. I don't have one on the rig but others will know the correct conditions for it to finish correctly.

[96 EVO]

Yeah, when that symbol lights up, keep driving, it will go out usually within 20min. If you shut the engine down while it's on, expect to see it again soon!

Which model coach do you have with a ISC 360HP?

[Gary M]

Here is a file on your Medallion Screen on your dash that may help you. Your manual should explain about the regen light.

Medallion-10 button ILB screens.pdf

Edited July 30, 2023 by Gary M

[Frank McElroy]

8 hours ago, DaKevster said:

New to me 2008 Hol Rambler 40PLQ with ISC360, Allison 3000. I just had a bunch of engine/chassis maint done; fluids, filters all changed. Have driven 150 miles since then with no issues. Today, was driving with no heavy load abt 15 mins and get this dash symbol. I have looked in the RV manuals, s byearched online, done reverse google image search, and I am coming up blank on what this means. There are the standard temp dial gauges on engine/trans that have the thermometer temp symbol. This is slightly different, with what looks like a blowing temp symbol. At the time trans temp was 161 and engine temp was 177 and gauges were all in the middle. Air pressures were fine. I'm stumped. Went abt 5 miles with that lit up and all seemed normal. Haven't tried starting/driving it since. Anyone know what this means or where to look up info?

 

That is the HEST light.  The High Exhaust System Temperature light comes on during a diesel particulate filter regeneration cycle to warn you that exhaust temperatures are above 1,450 degrees F.  Normally it takes about 20 minutes for the cycle to complete. 

Since it was only on for 5 minutes, you likely did not burn off all the soot in the DPF. 

Your engine computer will determine if the pressure drop across the DPF is high enough to restart another Regen the next time you drive. 

The best way to complete a Regen cycle is to drive at highway speed.  Speeds below about 40 mph, using the engine brake or climbing grades at full throttle will suspend the Regen cycle.  When the DPF dash light comes on it's telling you to drive the coach under conditions to do a DPF Regen.  (The DPF light doesn't necessarily mean the engine is actually doing a Regen.)

[DaKevster]

Thanks Frank for the detailed explanation. Glad it's an indicator light that means drive more, rather than pull over and call a tow truck. 😀 Looks like I need to break out the Cummins book and do some deep reading on DPF. 

Edited July 31, 2023 by DaKevster

[DaKevster]

On 7/29/2023 at 10:35 PM, 96 EVO said:

Yeah, when that symbol lights up, keep driving, it will go out usually within 20min. If you shut the engine down while it's on, expect to see it again soon!

Which model coach do you have with a ISC 360HP?

Its a 2008 Holiday Rambler Ambassador 40PLQ, with the ISC360. Yes, did have to shut 'er down while still lit, so will be seeing it again soon I presume.

On 7/29/2023 at 10:44 PM, Gary M said:

Here is a file on your Medallion Screen on your dash that may help you. Your manual should explain about the regen light.

Medallion-10 button ILB screens.pdf 1.6 MB · 11 downloads

Thanks for that Medallion manual!! I'd been digging and not finding anything on my particular dash in the box of manuals. Wasn't in Hol Rambler manual.

[Tom Cherry]

4 hours ago, DaKevster said:

Thanks Frank for the detailed explanation. Glad it's an indicator light that means drive more, rather than pull over and call a tow truck. 😀 Looks like I need to break out the Cummins book and do some deep reading on DPF. 

Frank is the expert.  But Cummins and Frank explained a bit more.

YES….IF you had to shut down, odds are, it will reappear again and then turn off.

YES….Perfectly NORMAL….On my ISL, the ECM is programmed (per Frank’s scanning my engine)  for 100 operating hours.

My FIRST regen spooked me.  I measured every nook and cranny of the exhaust and DPF….like a good retired engineer should and had a thesis of data to give to Cummins…tech guy said DRIVE IT….NORMAL….  BTW, I had driven a long way on a narrow road previously so the engine was not “at cruising speed”.  That MAY have prompted it, but Frank said the timer.

I had one really “spooky” episode a few regens later.  Hotter than blazes in Nebraska.  Regen light came on.  Drove almost 1 1/2 hours at 62 MPH on interstate.  Had to exit at a preplanned stop.  Stopped at stop sign on ramp.  Turned left and 100 yds was a traffic light.  It turned off when i did a normal acceleration.  Frank checked the log.  Started right on time.  No idea why, except really hot, it lasted that long.  Yes, the stupid light does bug me.  LOL.

[96 EVO]

I had one that had me concerned!

One of the regen lights came on as I was within a couple of mi of cresting a mountain pass. 7% downgrade on the other side, obviously I had to get off the throttle, and on the exhaust brake for several miles.

Lamp flashed all the way down, then went back to solid when I got back on the throttle. HEST came on, and stayed on for about 45min driving!

First and only time I've seen it illuminated for longer than 20min or so!

[Frank McElroy]

While driving at highway speeds, typically temperatures inside the DPF are high enough to burn off sort.  This is called passive regeneration.

The engine ECM is constantly monitoring the pressure drop across the stages of the DPF and time since the last Regen cycle.  If the pressure drop is too high, the engine will be commanded to do an active DPF Regen and the DPF light will come on to tell the driver to drive under conditions to do an active regen.

If about 100 hours of engine run time has passed since the last Regen, even if the pressure differential inside the DPF is low, the engine ECM will command an active regen and turn on the DPF light.

Not all active regen will turn on the HEST light.  This light only comes on in cases where the soot load is high enough or the pressure differential is not falling fast enough that the engine must dump in more diesel fuel to raise the temperature of the DPF above 1,450 deg F.  On a Cummins ISL raw fuel is added just before the end of the power stroke; on an ISX, there is a dosing fuel injector on the exhaust manifold.  That extra fuel is then ignited inside the DPF to raise the DPF temperature.

Ideally all regens should be at about 100 hours since the last Regen.  If regenerations are significantly less than 100 engine run hours (about 5,000 miles), that's the first indication that something is generating soot.  Could be a fuel injector, turbo, or EGR problem starting to develop.  That's why it's a good idea to look at the DPF regeneration history report about every year or so using Cummins Insite software.  It will be your first indication of a problem brewing.

Hope all this helps to better explain the system.

[DaKevster]

4 hours ago, Frank McElroy said:

While driving at highway speeds, typically temperatures inside the DPF are high enough to burn off sort.  This is called passive regeneration.

The engine ECM is constantly monitoring the pressure drop across the stages of the DPF and time since the last Regen cycle.  If the pressure drop is too high, the engine will be commanded to do an active DPF Regen and the DPF light will come on to tell the driver to drive under conditions to do an active regen.

If about 100 hours of engine run time has passed since the last Regen, even if the pressure differential inside the DPF is low, the engine ECM will command an active regen and turn on the DPF light.

Not all active regen will turn on the HEST light.  This light only comes on in cases where the soot load is high enough or the pressure differential is not falling fast enough that the engine must dump in more diesel fuel to raise the temperature of the DPF above 1,450 deg F.  On a Cummins ISL raw fuel is added just before the end of the power stroke; on an ISX, there is a dosing fuel injector on the exhaust manifold.  That extra fuel is then ignited inside the DPF to raise the DPF temperature.

Ideally all regens should be at about 100 hours since the last Regen.  If regenerations are significantly less than 100 engine run hours (about 5,000 miles), that's the first indication that something is generating soot.  Could be a fuel injector, turbo, or EGR problem starting to develop.  That's why it's a good idea to look at the DPF regeneration history report about every year or so using Cummins Insite software.  It will be your first indication of a problem brewing.

Hope all this helps to better explain the system.

Looking at the Insite software now. Looks worthwhile. Any suggestions on a RP1210 Compliant Datalink Adapter? A little googling finds a couple sources that are several hundred bucks.