Exhaust Brake Unavailable

[Markh1254]

I hate to impose again on this group again but I am unsure if I have a problem or not with this RAM I picked up late last year. It's a 2500 Tradesman with the 6.7L Cummins. I've never owned a diesel truck before and am on a learning curve and appreciate any and all advice!

Yesterday we took the truck for a drive and while running down the highway as we were going down a grade I decided to see how the exhaust brake works. As soon as I engaged it on the dash I got a message "Exhaust Brake Unavailable". We were doing about 75 MPH and obviously it made no difference since it gave me that message.

I've read the manual and looked at some YouTube videos and not sure what, if anything I did wrong. I get no error messages on the dash indicating any faults, other then the exhaust brake error when I attempt to us it.

What am I missing?

Thank you again and please pardon my ignorance.

Mark

 

[TMyers]

My RPM's have to be above 1400 before my EB will kick in. Have you lost power or does the truck feel sluggish taking off? Is the turbo gaining boost when accelerating?

These are signs of your turbo actuator going out which controls both the boost and EB. But, it should throw a code.

 

[gsbrockman]

First time I’ve ever heard of “exhaust brake unavailable.”

 

[EZeis]

You never used it before? How long have you had the truck? Any codes?

Earl

 

[Markh1254]

My RPM's have to be above 1400 before my EB will kick in. Have you lost power or does the truck feel sluggish taking off? Is the turbo gaining boost when accelerating?

These are signs of your turbo actuator going out which controls both the boost and EB. But, it should throw a code.

I show boost pressure when accelerating and there is no sign of any sluggishness. I have no codes. Truck runs great otherwise.

 

[Markh1254]

You never used it before? How long have you had the truck? Any codes?

Earl

Just purchased the truck in Fall and haven't driven it on the salt laden winter roads in NE Ohio. Took it for a 300 mile drive and it ran just fine. No codes displayed that I'm aware of. Would they be displayed on the dash?

 

[EZeis]

Just purchased the truck in Fall and haven't driven it on the salt laden winter roads in NE Ohio. Took it for a 300 mile drive and it ran just fine. No codes displayed that I'm aware of. Would they be displayed on the dash?

You'd need to use a scan tool to see if there are my codes. Not all codes will cause a check engine light.

I run my exhaust brake all the time. I also run tow/hail mode all the time for better exhaust braking.

Earl

 

[Jim W]

What gear and what was your engine RPM's as you were going down hill. My exhaust break will disengage at 1,100 RPM's regardless of what gear I am in. But when I downshift to a lower gear say from 6th to 5th the engine RPM's will increase, thus I can keep the exhaust brake functioning.

 

[Cummins12V98]

You also need to turn on the Tow Haul button to keep the RPM's up enough for the EB to work.

 

[TMyers]

As mentioned earlier, I keep my truck's Tow and Haul and the EB on as well. Keeps the turbo gate moving freely and saves brakes. Plus, I tow a lot.

There was a program rewrite/update a few years ago that cycles the turbo actuator upon startup. I want to think it was in 2017. The dealership did the update on my truck when they did the tailgate lock recall. I think the OP's truck would throw a code at startup if the actuator wasn't moving full range.

Also, I've never seen, "Exhaust Brake Unavailable" either and I went through all the codes and a bad actuator a couple years ago.

 

[Ozymandias]

Just purchased the truck in Fall and haven't driven it on the salt laden winter roads in NE Ohio. Took it for a 300 mile drive and it ran just fine. No codes displayed that I'm aware of. Would they be displayed on the dash?

No, you have to see a dealer. 95% of all codes don't show up as a MIL light.

 

[AH64ID]

You also need to turn on the Tow Haul button to keep the RPM's up enough for the EB to work.

Not really true. There is no “need” to run the EB with TH. I run the EB often without TH and it works just fine. It’s a different downshift schedule, but it still works without TH.

 

[Markh1254]

Using the OBDLinkMX+ and AlfaOBD I went into the ECM and checked for codes, I had one related to the RF wireless hub that it was temporarily unavailable.. I did cycle the turbo actuator and was able to hear it moving.

 

[Cummins12V98]

Not really true. There is no “need” to run the EB with TH. I run the EB often without TH and it works just fine. It’s a different downshift schedule, but it still works without TH.

with the 68rfe the rpm would drop very low if the TH was not applied and the EB was basically useless.

Maybe AISIN is different.

 

[Cummins12V98]

with the 68rfe the rpm would drop very low if the TH was not applied and the EB was basically useless.

Maybe AISIN is different.

For me the AISIN and EB are best when TH and EB both are applied.

For my use the Auto mode is useless.

 

[TMyers]

For me the AISIN and EB are best when TH and EB both are applied.

For my use the Auto mode is useless.

Please help me understand Auto vs. Manual mode. I keep my EB on Auto. When I let off the fuel, the Auto EB will not let my truck exceed that speed. In Manual EB, I tap my brake pedal and that is the speed my truck will not exceed. I this correct or am I missing something?

 

[Cummins12V98]

I tow too heavy for either to hold me on steep grades. I use cruise control and a selected gear to control downhill speed.

 

[Markh1254]

Problem solved...operator error. What I thought was Exhaust Brake actually is Hill Descent which won't work without the Exhaust Brake engaged. Duh!!!

 

[Ozymandias]

 

[EZeis]

Not really true. There is no “need” to run the EB with TH. I run the EB often without TH and it works just fine. It’s a different downshift schedule, but it still works without TH.

Isn't the same at all. Hardly any braking without tow/haul mode enabled. Night and day. Unless your truck has an issue. I can only get good breaking on tow/haul. Too weak to bother without tow/haul.

Earl