Community Forums

Wadell · 02-15-2022, 10:15 PM

Well, its put back together, new jumper and ready to test tomorrow. Added the missing engine brake A and B wires. AND added the "exhaust brake enable" wire back into the Engine brake B circuit. And the reason why is the added schematic portion. The exhaust brake enable wire when powered kicks this latching circuit to turn on the brake lamps while engine braking.

The exhaust brake NC comes off the VIM relay box, the relay is fired from the TCM. I have a relay missing in the front run box will explore what that could be another day.

There are 2 places the engine and chassis computers effect each other. The VIM is the relay box, and the "Oval connector" The oval connector is where the switches tell the TCM to operate a relay in the VIM. When looking at the transmission schematics these IF/THENS are not specified (except for the neutral safety and back up beeper) and because the Allison transmission is used in many different vehicles, the VIM would need to do different things.

BigEd1957 · 02-16-2022, 11:30 AM

No butt splices on mine, all factory looking. On the sensors, I had the Intake Manifold Sensor replaced by Cummins while we were on a trip to Florida in the fall of 2020. $95 for the sensor and 2 hrs labor. Total of $454. After I retired in January of 2021, I bought a diagnostic laptop off ebay. Kind of handy to have. I looked up the sensors on ebay and Amazon and they were much cheaper. Doing a Google search led me to Auto Zone.

Ed

Quick68 · 02-16-2022, 08:22 PM

Quote:

Originally Posted by BigEd1957

Is the check engine light on? I have an 04 Holiday Rambler Imperial with the 400 ISL and a 2 stage compression brake. Last year I had the check engine light come on and the engine brake and cruise control wouldn't work. Plugged Cummins Insite into it and it had thrown a code 433 for Intake Manifold Sensor too high or low reading. Went to Auto Zone and $23 later I had a new sensor, put it in, started it and about a minute later the check engine light went out. Took it for a test drive and the jake and cruise worked fine. Several months later it quit working again due to a check engine light. This time it was the Barometric Pressure sensor. Another $37 at Auto Zone. Put it in, started it up and a minute later the check engine light went out. The jake and cruise worked fine again on the test ride. There are numerous codes that when thrown by the ECM, the jake won't work. Good Luck with your tests.

Ed

Hi Ed.
Thank you for your input. This information will be very helpful to another reader in need of help Diagnosing a similar problem in the future.
Thanks.
Frank.

BigEd1957 · 02-17-2022, 09:11 AM

Quote:

Originally Posted by Quick68

Hi Ed.
Thank you for your input. This information will be very helpful to another reader in need of help Diagnosing a similar problem in the future.
Thanks.
Frank.

Thanks Frank. I have been a Lurker on IRV2 for close to 15 years, never really having time to join, but researching issues with my bus that others have already conquered. Since I retired, I have more time and can hopefully add to the wonderful community here.

I forgot to mention, the $95 Cummins sensor only lasted 3 months before going bad in early 2021. That's when I bought the diagnostic computer, plugged it into the bus and learned how to use it. The sensors at Auto Zone have been installed for a year with no problems. The laptop cost was paid for by not going to a Cummins shop, which in my neck of the woods is a 2-3 hour drive depending where I go. So it's not only the cost of the repair, it's the time and fuel spent getting there.

Our bus is 17 years old now and has 95,000 miles on it. Been trouble free except for the standard lift pump issues with the Caps and now these sensors. A lot of minor repairs are made easier to do with the proper equipment and the knowledge provided by the generous folks here on IRV2.

Ed

Wadell · 02-20-2022, 09:12 PM

So, with the repaired wires, the compression brake worked. At least for half the trip down. The connections were hurried and probably fell back apart. Have to crawl back under there and check those connections, I was not able to check with the extra wire disconnected. IF i were to guess, the jake would work, but the brakes lights wouldn't come on.

I will look for an Insite computer, could be interesting... kinda ran into another issue one the way back , Idle boost PSI 19 and wide open 24. this could be that sensor or turbo.... hope its a sensor.

Lowflyer1 · 02-21-2022, 05:30 AM

For just a code reader, you might want to consider some generic products such as "NEXAS NL102 Plus Heavy Duty Truck Scan Tool".

These are fraction of the cost of a Cummins Insite and us casual users don't need all that capability the Insite has.

Wadell · 02-27-2022, 08:42 PM

So, for a quick update, The manifold pressure sensor had failed. Turn the ignition on with engine off, read 19-20psi. When reading thru the symptom trouble shooting pages of the quickserve, there was a mention to check the boost pressure, to have the compression brake work. That got me thinking about the pressure sensor reading wrong, and the computer thinking the high reading at idle causes the computer to "think" the pressure is high and not allowing the compression brake to work. Going to test drive incase the KM sensor is not good before the next trip.