Curious ECM/VPM behavior on a 1997 International 3400 T444E

[JenniferWillow]

Hi everyone,
I’m in a curious situation. I have a 1997 International 3400 T444e bus manufactured by Midbus. I’ve got BlueFire connected and a Nexiq USB link 3 that connects to the 1708 bus. I’m reading parameters, displaying telemetry on a custom dash, etc.. I thought everything was OK with my ECM but 2 weeks ago we were on a trip about 70 miles from home and the bus slowed to 20 mph on the freeway. I got off the expressway and took it to the first diesel shop I could find. They read codes (not sure what software) (5 total, 4 related) that indicated no communication between the ECM and the VPM, corrupt KAM memory and running on defaults. All the codes were inactive. The next morning we headed back and the bus stalled just after going through an intersection. We pulled over and started to arrange a tow with Coachnet. After about 15 minutes we tried starting it again and it started right up. We drove the rest of the way home with no problems.
So how is this curious? Sounds like any other problem right? Well first I checked the BlueFire app and there were no codes? I said Ok, maybe I need proprietary software to read the code? Maybe it’s BlueFire? I called a diesel mechanic to come out and on the first visit they didn’t have the right laptop with ServiceMaxx 1708. They came back a week later with the old laptop and it wouldn’t connect. They charged me nothing. Nice guys. So I ordered the Nexiq and setup ServiceMaxx on my Windows laptop and tried to connect to the bus. It connected immediately (just like BlueFire). So I’m happy until I try to read DTC codes….. nothing

summary:
BlueFire : no DTC codes, good telemetry, easy connection
DieselDoctor : can’t connect
ServiceMaxx 1708 : no codes, good telemetry, easy connection

I’m getting plenty of communication, lots of telemetry (oil pressure, water temp, etc), and I can see and plot damn near any value I can think of but NO DTC CODES. The bus clearly had a problem that should have thrown a few codes but nothing. All the codes I got from the first diesel shop were acquired by the press diagnostic button and turn on key procedure (counting light blinks) which bypasses the VPM. I’m assuming that I’ve got some wiring problem between VPM and the ECM, or more likely a bad VPM, ECM or both. But why am I getting all the telemetry but not the codes?

Best Possibility: The shop in Ventura cleared the codes when they manually read them. There have been no DTC codes thrown since (despite stalling out for 15 minutes on the side of the road). Likelihood ~ 10 percent (actually less)
Worst possibility: The ECM, VPM and the harness between them needs to be replaced.

What’s curious about this is that as far as BlueFire and ServiceMaxx are concerned there are no DTC codes thrown. The bus is running fine but it’s not. The codes read “manually” (I.e light blinks) come from the ECM directly so I’m inclined to trust them.
Question: Has anyone been able to connect and get telemetry (fuel consumption, water temperature, etc)on the J1708 bus but not been able to read DTC codes? Has anyone been able to connect, get telemetry but not DTC? on any 1990’s bus.`

So do I have to spend several thousand to update/replace the ECM, VPM so I can read codes? I know the bus bus won’t last 6 months on the road if nobody can read the codes. If nikitis sees this I’m in almost exactly your situation the night before you took yours to the International dealer. I’m headed in to the local dealership tomorrow morning. I’m hoping, **** I don’t know what I’m hoping for. Maybe this, tell me to replace / rebuild both the ECM and the VPM for the absolute minimum cost (the diagnosis not the cost of the hardware).

Thanks for reading. I hope someone knows something about systems where you can’t read DTC codes and how to fix them.

 

[BamaBus]

Not all issues will cause a fault code to be set by the ecm. Have you tried to read any codes by using the diagnostic button? You should get at least 111 that way.

 

[Diverdude0075]

Following. I have two ‘99 Internationals with the 7.3. I think my ECMs are different than yours. Curious what you figure out though.

 

[ewo1]

Start your troubleshooting from the basics...step one...make sure you got clean power and grounds. Open them up, clean them up, don't just do a visual. Check your fuse pigtails too!

Once you verified clean power then you can go to step two...guessing!

Seriously, always start from step one.

 

[Mr P]

In the automotive world certain codes will "self clear" after a certain amount of driving.

What were the code numbers the diesel shop found?

 

[desrtdog]

@ewo1 is spot on…. Check your electrical connections before assuming something else.

I have been chasing some electrical gremlins on my Cummins 6.7 after having similar symptoms (engine power loss, stalling)…error codes for me pointed to a loss of electrical power to ECM, but codes always go to inactive when bus is restarted, so difficult to troubleshoot. Pulled and cleaned all the grounds, cleaned terminal connectors and changed a fuse…still not sure what the root cause is/was, other than something electrical…

So, check the obvious first…

 

[Mr P]

Step one from a multi decade auto tech, check codes. The reason that I want codes is to see what, if any, circuits are common between codes. Then the most likely connections could be checked first.

That's why I asked what codes the shop found...

 

[Dbacks2k4]

Electrical gremlins from loose connectors or other issues that don't throw DTCs are the most "fun" issues to track down... One of my intact DT466e's had a faulty EGR valve that didn't throw a code. The valve was reporting movement fine, but wasn't actually closing. Another had a wire harness going to the IPR that was coming loose when it got hot. No codes on that either.

 

[JenniferWillow]

Thanks for all of the comments. Well it cost me about $1850.00 at the International dealership and all of my worry about the ECM was largely misplaced. They pulled the ECM and updated the code with NavKal to the most recent version. The version of code on the ECM was the very oldest available and was largely responsible for the software not being able to read DTC’s. The update will hopefully help with diagnosing issues.
The real problem we had was a plugged up secondary fuel filter and that was responsible for both the breakdown incidents. I should have immediately recognized this as a fuel delivery problem. I’m expecting things to throw codes but they don’t. It’s my own inexperience talking.

 

[JenniferWillow]

Step one from a multi decade auto tech, check codes. The reason that I want codes is to see what, if any, circuits are common between codes. Then the most likely connections could be checked first.

That's why I asked what codes the shop found...

You’re right that I should have posted the actual codes last night. They were out in the bus and I was too lazy to go get the paperwork.

These are the codes they reported:

SID 254 Keep Alive Memory (KAM) in ECM is corrupt
SID 34. Exhaust Back Pressure (EP above specification
SID 252 Vehicle Personality Module not communicating with ECM
SID 253 Engine using field default rating
SID 254 programmable parameter in Keep Alive Memory (KAM) is corrupting power to KAM is ok, replace ECM

I think you see why I was worried about the ECM.

 

[JenniferWillow]

Not all issues will cause a fault code to be set by the ecm. Have you tried to read any codes by using the diagnostic button? You should get at least 111 that way.

Yes, I tried that and I did get a 111.

 

[JenniferWillow]

Electrical gremlins from loose connectors or other issues that don't throw DTCs are the most "fun" issues to track down... One of my intact DT466e's had a faulty EGR valve that didn't throw a code. The valve was reporting movement fine, but wasn't actually closing. Another had a wire harness going to the IPR that was coming loose when it got hot. No codes on that either.

Since the bus is an early 3 box system I suspect that it just doesn’t throw the same number of codes as a more recent 7.3 powerstroke. I’m new to diesel engines and I just don’t have the experience yet to know how frequently these engines throw codes.