Sporadic Fault Codes….

[desrtdog]

@desrtdog If you do end up with a new ECM, I wouldn't mind taking a look at your old ECM for science. If you aren't turning it in as a core replacement, and are willing to ship it to me, I would take it apart and see if I can see any broken traces on the board, and could repair it and would send it back to you as a spare if I did find any damage, and repair it for you. I'd like to create a thread on ECM repair on here.

At the very least I could confirm if it was a chip failure or board failure for you.

Appreciate the offer - I’ll let you know once I know more. Right now, I need to get a computer on it, then assuming it is the ECM, get a replacement. There’s a place near me in Houston that has refurbished ones with a “lifetime” warranty - pricey, but piece of mind. I am also looking at procuring one from a scrap bus (the guy that @ewo1 referenced in different post) in the next week or so (whenever the buses arrive)… $300, but would still likely require programming.

Stay tuned…

 

[ewo1]

ROM - resources


A Cummins ISB Engine Control Unit (ECU) being "ROM booted" refers to a special operating mode where the ECU enters a bootloader environment to recover or reprogram its firmware, often due to a corrupted or incomplete calibration download.

• What it means:
  The ECU enters a ROM boot mode when its main operating software is damaged, perhaps during a failed calibration update.
• Recovery:
  A tool like Cummins INSITE or other specialized software, along with a valid calibration file and appropriate hardware (like boot cables), is needed to recover the ECU.

Cummins cm2250 rom boot diagram​

https://mhhauto.com/Thread-Urgent-Cummins-cm2250-rom-boot-diagram

PCM, ECU, FICM, and ECM Programming Harnesses

Browse our selection of PCM, ECU, and ECM programming harnesses. We continue to add harnesses to meet and exceed your programming, tuning, and remapping needs.

bench-force.com

 

[ewo1]

Remember when the mechanic talked to you about heat damaging the ECU?
Heat is the #1 destroyer of solder joints !

Complaint of engine will not start.
The password protection is a result of a solder joint failure. When the solder joint fails it corrupts the portion of the memory where the password is stored, and the ECM goes into a password protected state. Corruption of the memory makes the ECM inoperative.

If they tell you ECU is toast, have them verify if there are solder cracks on the board. Best way to do the visual is with a simple "lighted" magnifying glass.

 

[ewo1]

SCHOOL BUS-BAD MOTOR MOUNTS - EFFECTS ON ECU

Failed engine mounts may cause vibration on ISB6.7 CM2150 engines in school bus.

The vibration from damaged engine mounts can cause an internal malfunction to the engine control module (ECM) and the ECM may be in a ROM Boot State or “Will Not Communicate”

Before replacing the ECM, inspect the condition of the engine mounts. If the engine mounts are in good condition, continue with the repair

 

[nikitis]

SCHOOL BUS-BAD MOTOR MOUNTS - EFFECTS ON ECU

Failed engine mounts may cause vibration on ISB6.7 CM2150 engines in school bus.

The vibration from damaged engine mounts can cause an internal malfunction to the engine control module (ECM) and the ECM may be in a ROM Boot State or “Will Not Communicate”

Before replacing the ECM, inspect the condition of the engine mounts. If the engine mounts are in good condition, continue with the repair

Yet another reason it's really stupid to mount the ECU on the engine.

 

[ewo1]

Yet another reason it's really stupid to mount the ECU on the engine.

On the flip side of that thought, now would be a good time to check you motor mounts. This is one topic I really never seen anyone discuss!

 

[nikitis]

I don't recommend anyone actually go and do this unless you're confident in doing electrical extensions, but if I owned a 1Box and I saw my ECM on the engine like that I'd remove it, cut the harness in half one wire at a time, and extend the harness all the way to inside of my Dash inside of my firewall.

 

[ewo1]

I don't recommend anyone actually go and do this unless you're confident in doing electrical extensions, but if I owned a 1Box and I saw my ECM on the engine like that I'd remove it, cut the harness in half one wire at a time, and extend the harness all the way to inside of my Dash inside of my firewall.

And it's gonna bounce around just the same as if the motor mounts were good.
What's the point?

 

[desrtdog]

An update here … (have exchanged messages with @ewo1 regarding this, but thought it would be good to post here)…

After no success finding a spare ECM to try, I pulled mine last week and brought it to a repair place on Friday morning. Left it there with the understanding that in 3-5 business days they’d check it and repair if possible, otherwise I’d get a replacement (refurbished with all new innards and programmed).

Got a call Friday afternoon saying they needed to reprogram it as it was “ROM booted” and would not communicate…gave the ok for that ($200), and waiting to hear from them sometime this week.

In the meantime, had a couple back-and-forth texts about this and @ewo1 was kind enough to post the above docs….from one of these (Cummins TSB 140079 the one in post #124) it almost seems like I should replace the ECM…

As it was after hours on Friday, I was not able to contact Cummins tech support to get more info on this, so plan to call tomorrow morning, and also call the repair place to let them know whether to proceed or just get a replacement… more to come on this…

 

[nikitis]

And it's gonna bounce around just the same as if the motor mounts were good.
What's the point?

I think it would bounce around far less inside of a dash than mounted to an engine.

Also that's not the only point to consider.

Heat.

It's far cooler inside the dash. Heat could help with corrosion of pins faster.

 

[desrtdog]

So update here…
Last week I got a call saying that the ECM was toast - they could not establish any comms - so gave the go for a replacement. Replacement ECM arrived today - will be a couple of days before I can install as I may need to take it in to get a couple of programming changes…distance and time offsets for the engine, as well as tire size (currently reflecting 641 revs/mile, which seems like 18” wheels vs the 22.5 low profiles that I have, which would be more like 560 revs/mile).

Interesting thing here is that when they programmed the ECM, they did so based on a code provided by Cummins for my engine s/n. In doing this, I now have an ECM program that has upped the power and torque vs the previous…previously, this was set to 220 Hp / 520 ft-lb … now at 280 / 660. Checked engine specs and the 6.7 ISB is good for 200-350 Hp and 500-750 ft-lb, so ok there. The 2500PTS is rated for max 300Hp and 660 ft-lb (with torque control) or 550 ft-lb (without) …not sure if I’ve got the torque control on mine, so may have that bumped down to 550.

Get this stuff done then all I gotta do is hope the problem is fixed…

 

[nikitis]

So this happened to me when I had to replace my VPM which is the equivilant of your ECM 1 box. They flashed it back to what Navistar had on file for my VIN number which was 40 MPH limitation, etc. It was terrible. I had to go back and get them to fix it. They tried to charge me but it wasn't set there when I brought it in, so I made them do it for free. Had a spout with a manager there but I won. If there's any settings that weren't there before they need to set those back to the way it was. You shouldn't have to pay for features twice.

You may not have paid for those upgrades, but the previous owner did.

 

[desrtdog]

Already talked to them when I picked it up, and again after I talked to Cummins…they said that although they typically just program per Cummins specs for the particular ESN, they’d changes the offsets and tire size…mentioned my initial concern about the hp and torque, and believe they’d probably reduce the torque if I asked…

Oh, and on the old ECM - I turned that in for a core, so all in it cost me 1295 + tax…

 

[BamaBus]

Recently I called Cummins concerning a bad ecm and asked about swapping in a known good ecm. She said she couldn't recommend that for liabilty and the problem may be a short in the wiring that caused the issue.

 

[desrtdog]

Yeah, I went through the wiring pretty extensively as well as several Cummins troubleshooting procedures to try to diagnose the problems before finally removing the ECM for testing - and this was only done after finding a video of a guy diagnosing a bus similar to mine with the exact same symptoms…

Now, if I had a computer with INSITE software, I’d probably figured this out sooner….

 

[nikitis]

Recently I called Cummins concerning a bad ecm and asked about swapping in a known good ecm. She said she couldn't recommend that for liabilty and the problem may be a short in the wiring that caused the issue.

Not like "They" are gonna check for faulty wiring. They're just gonna drop one in. Only if you come back with problems after drop in would they go that route and for extra hours.

Yeah, I went through the wiring pretty extensively as well as several Cummins troubleshooting procedures to try to diagnose the problems before finally removing the ECM for testing - and this was only done after finding a video of a guy diagnosing a bus similar to mine with the exact same symptoms…

Now, if I had a computer with INSITE software, I’d probably figured this out sooner….

I did wiring testing as well first to know it was the VPM same as we directed you to check as well. Wire testing should be first. Much cheaper option if it's the issue.

 

[desrtdog]

Dropped the ECM back at GoECM to have them enter the mileage and time offsets, as well as update the tire size based on my tires (22.5 low profiles). Also going to get the torque reduced to 550 as I am not certain that my trans has Torque Management - the guy who reprogrammed for 6th gear said the program does not, so out of abundance of caution, not going to risk exceeding Allison’s specs…

 

[desrtdog]

So, latest on the ECM…dropped it back last week o update mileage and hours, and change the tire size, as well as reduce torque max. Hours and tire size got updated but not mileage; torque is a locked value that requires a different ECM calibration.

Checked with the guy who reprogrammed my TCM and he said it did not have shift energy management (torque management) … asked if it could be programmed and he said that it can be turned on but could throw errors and fail to shift if not in the original program….some other stuff about an engine/trans mismatch …. so, while the trans might theoretically be ok leaving the TCM as is (keep the 280/660 cal in the ECM) and go easy on the acceleration (hill climbing, etc), I have come to the realization that I don’t really want to risk breaking something for the sake of more hp…

I asked GoECM to reprogram to the original code - so back to 220/520…hoping they can get it done in the next day or so…

 

[Kentucky Dreaming]

Dadgummit. That sux.

 

[desrtdog]

So, jut closing this thread out…got the new ECM reprogrammed back to the original 220/520, and installed. Bus started right up (good news),but gave me another error code related to the Vehicle Speed Sensor (documented in a separate thread). Long story short, the fault was related to an incorrect selection in the ECM programming, which has since been corrected…

The Dominic is back in business, baby!!!