Sporadic Fault Codes….

[ewo1]

Here is another related read, in this one cadillackid chimed in on something that we covered yesterdy, testing the backbone.

an open wire in the network would drop only one device.. a fuse blow would be a constant down all the time. (unless its a circuit breaker trip.. but since the bus does start we know the ECM has power or the engine wouldnt run)...

so we verified that it is not just an open leg on the backbone... why you got an ABS fail message ???
ECM tripping on LSD ???

2007 Bluebird Vision/ Engine Comm Failure, Trans Comm Failure, ABS Comm Failure

I have a 2007 Bluebird Vision with a C7 Acert engine and Allison transmission. When I turn the key to the run position (without starting) the speedometer reads engine comm failure, trans comm failure, and ABS comm failure. All of the gauges start sweeping. The bus can be started, however the...

www.skoolie.net

This one comment in post #5 posted by Booyah45828, makes a really good strong point....

The visions had issues with the fuse holders at the multiplex being loose/corroded and causing this.​

This makes alot of sense especially since your issue started as an intermittent problem.. I would try to do a visual inspection of the back of that panel. I would move/jiggle the wiring behind and turn the key to see if anything comes to life or not. Check for "Darkened" connectors on the wires especially the terminals where the fuses slide in. discoloring is heat and heat degrades electrical connections.

 

[ewo1]

If you do go ahead and have the ECM replaced/programmed, take a read at this info.
Not 100% sure what it all means...

I got a new ecm and brought both ecms to a dealer to have the new one programmed. The old ecm is in bootrom which essential means there is no data to be transferred
The Cummins dealer can only put in the files for the Cummins side, not the bus side

CUMMINS ECM BLUEBIRD VISION

1

mhhauto.com

 

[ewo1]

I was looking thru the Vol 2 service manual again, page 826, pdf page 362, and what I see is that the dash cluster receives most of its data via the J1939. As i posted up earlier, the J1587 is read only (like we guessed it was).


Pin #2 on the dash connector "A" is your chassis ground.
Pins 1,3 & 4 seem to be power inputs.

Connector "B" are inputs from air pressure, water in fuel, ammeter, fuel.

when you turn the key does the fuel gauge work?

Connector "C", this one interests me..
This is where the ABS info goes... You did have an ABS failure message....no?

Is it possible that the multiplexer has a loose wiring problem??? IDK...


next page (827), pins 1&3 is for dash power. Dash is lit up ok so I do not think you need to go there.

mentioned earlier about doing the onboard diagnostics. I think this is worth trying. If the dash can perform its diagnostics then it is obviously communicating via the J1939 and also relaying messages ia the J1857

we verified the data link so I feel that any further communication failure just might be the ECU...

 

[desrtdog]

Here is an interesting "related" read, his fix was ECM. States that heat killed 2 of them...

2008 Bluebird eng quit - School Bus Fleet Magazine Forums

So, when I had the bus at the shop in Kerrville in April, mechanic did mention that heat can kill the ECM, but he also checked the temp of it with an IR while running gauge and said it was fine…but maybe 15 years of combined Texas use took its toll?

 

[nikitis]

That's the one sole advantage the 3box has over the modern buses is the computer locations are father away from the engine. I've complained about this in the past. 1 Box ecm systems are right on top of the engine practically.

 

[ewo1]

I made a call to Central States bus sales tech support line, 800-825-8273, and asked if they could tell me where the resistors are actually located.
He was not sure , said it was an older bus but he asked for the body number and checked...
His diagrams shows exactly what we already have but he did state that the usual places are...
A) under the dash cluster
b) attached to the wiring harness near the ECU
c) in the TCM
d) inside the VGT controller.

I asked him if it would be a blue housing for the resistor he stated OEM were blue but are now black in color.

I would look closer at the wiring loom going to the ecm, open the loom to see if the resistor is in fact in there...or maybe damaged wiring.
I would also follow the VGT wiring to see if the resistor is hidden inside the loom at that location.

He indicated that there might be more than two resistors in the backbone circuit but then I questioned his statement...how can you get 120 ohms on each end and 60 ohms when measured in parallel with 3 or 4 resistors in different locations.....he didn't have an answer...

I asked him about the TACH, does it move while cranking and he quickly said yes it does as well as the oil pressure gauge.

Does anyone out there have a BB vision that can verify this on their bus, a 2010?

We talked about the codes, 0435 & 1117 (historical)...and all the testing that was done on the datalink cable.

His first impression was that the ECU has died. suggested we try swapping it to another motor or using a different ECU to see what is going on...

 

[desrtdog]

Went through a retest of yesterday's exercise just to reconfirm what was observed, and record readings. Here are the steps I went through and results:

1. Measured voltages at ECM: 12.7v at 4-pin (battery supply) connector; 12.5v at pin 45 of OEM connector (with ignition on).
2. Measured CAN high and low voltages at pins C/A and D/A on diagnostic port: 2.62v and 2.44v, respectively w/ ignition on.
3. Disconnected batteries and measured resistance across diagnostic connector pins C/D: 26 ohms initially, up to 39 ohms on recheck. This is odd, because with everthing connected, should be close to 60…(showed 57 at end of testing yesterday).
4. Continued to measure resistance while sequential disconnecting modules: Instrument Cluster (C302) - went up to 101.6; ABS connector - no change (101.6); ECM - 102.3; TCM - open circuit; VGT connector - open circuit.
5. For giggles, I also checked the resistance at pins 15/16 of the instrument cluster (labeled connection “A” on the back of the cluster) … these pins correspond to the J1939 terminals on the connector: 106 ohms.
6. Also back checked resistance from the VGT plug J1939 wires (pins 3/4, I believe) … this goes back to terminals 38/39 of the ECM engine connector (the other up pin connector going to my ECM): 103.5 ohms
7. Checked continuity of each module above by shorting the J1939 pins at the harness connector and measuring at the diagnostic port. All came back at 0 ohms, indicating the J1939 wiring is intact.
8. To further test the continuity, I load tested the wires individually to the connectors with a light bulb. Again, all looked good - nice bright bulb.
9. Reconnected each connector in reverse order and measured system resistance of the J1939 network: starting with open circuit, connect TCM: 112.7 ohms; ECM: 112.3 ohms; ABS: 111.9 ohms; Instrument Cluster: 50-52 ohms. Hmmmm…
10. Reconnected batteries; still have COMM FAIL message, ABS light and crank/no-start.

Points 4&5 above would tend to imply that the termination resistors are internal to the TCM (which is noted on one of the wiring diagrams) and the instrument cluster … my instrument cluster is a single enclosed unit, which I have not yet tried to open…
Point 6 above is puzzling as the Cummins wiring diagram for my engine clearly shows what they are calling a “terminating resistor” which ties into the engine side of the ECM … not sure how or if this relates to the comms backbone…
Point 9 above is odd, because yesterday after all the testing and reconnecting, final resistance was ~57 ohms, so basically half of the value before connecting the final module.

Following all of this, I tried using the fault diagnostics feature on my instrument panel …. Have the ability to look at what are termed “engine”, “gear box” and “brake” … got nothing on any of them - i.e., no faults - whereas when I previously looked at these, I was getting a 231-14 code on the brake one only.

I also grabbed the following I/O diagnostics from the multiplexer:
A1I06 / A1O- / A1FB (all) / A2I- / A2O03 / A2FB (all but 2&3) / A3I- / A3O- / A3FB (all but 2&4).

Finally, here is a video of the engine cranking after all the testing… I know that some have said the tach and oil pressure should show response when cranking - I have personally noticed this previously when the bus did start … just did not pay that close attention to it as the bus would start within a couple of seconds…

(edit…having trouble with the attachment…)

 

[desrtdog]

Video from yesterday:
Crank/No-start

As you can see, the gauge sweep is fine, but no response on the tach or oil pressure when cranking.
Reading a bit about the instrument cluster, gauge sweep happens at ignition on and is an internal self-test that is independent of the ECM … at least according to my read of the manual and from dr google ….

 

[ewo1]

Dr Google...LOL....

what happened to Dr Vinnie Boombatz

Seriously though, i just had a virtual visit with Dr. google and he said this...

question asked: does tach move on a bluebird vision bus when cranking?

No, the tachometer (tach) needle on a Bluebird Vision bus will not move when the engine is cranking. The tachometer only indicates engine speed (RPM) when the engine is running, not during the cranking phase when the engine is starting but not yet running.
???

 

[nikitis]

Video is private, cannot view.

 

[desrtdog]

Video should be good now…

 

[nikitis]

Video should be good now…

Yeah it's interesting cause the ECM appears to be working because the gauge cluster does it's reset, and then finds it's values, but I dunno. Might just be a small part of something on the ECM that's broken so it's partially working. Might be time to get the ECM tested by a dealer.

 

[desrtdog]

Possibly a breakthrough (?)….

So, the other day we tested and retested the J1939 datalink forward and backward for continuity, and that all came back as expected - no broken wires in the cable.

Did a little more digging yesterday and came across a Cummins troubleshooting procedure related to the J1939 (procedure 019-165) which focuses on checking the datalink relative to the OEM harness to the ECM. (This is one of the two 60-pin harnesses to the ECM - the other being the “Engine” harness.) The procedure has you check:

1. The continuity of the J1939 + and - wires from the harness connector (pins 1 & 21) to their respective counterparts at the 9-pin diagnostic port (C &D). Checked fine…
2. Shorts to ground - i.e., pins 1 & 21 to chassis or engine block. These should show an open circuit, which Cummins defines as 100k ohms or greater… my result: 12.56k ohms …. Seems like a problem, maybe…
3. Shorts between the OEM J1939 pins and all other pins in the OEM connector, with a short again defined as any reading less than 100k ohms. For reference, only 29 of the 60 slots in that connector have wires. Of these, I found 9 wires that had resistance readings relative to pins 1 & 21 (J1939 + & -) ranging from 12k to 20k ohms …

For reference the applicable pins are: 2, 18, 29, 32, 39, 45, 52, 53 and 55. Pins 2, 18 and 55 go to the multiplex module; 52 and 32 are related to the fan clutch; 29 and 39 are related to the J1587 network; 45 is the ECM power from the ignition switch; and 53 feeds the “wait to start” lamp on the instrument cluster.

This is where it gets interesting… with the exception of pin 45, all of those wires go through connector C701 which is one of 4 plug penetrations through the firewall just above the multiplexer…

Not certain if this is in fact the source of my comms problem…guessing that this could be a slow / intermittent short to ground, which might explain why I see the J1939 circuit resistance start low when I first measure it, then creep upwards…Only way to really tell is to get into that connector and associated wiring. Could it also be a bad ECM, and if so, why just those pins?

Will leave it there for now and look a little more at the wiring diagrams, but appreciate any input / comments…

 

[desrtdog]

Video is private, cannot view.

Yeah it's interesting cause the ECM appears to be working because the gauge cluster does it's reset, and then finds it's values, but I dunno. Might just be a small part of something on the ECM that's broken so it's partially working. Might be time to get the ECM tested by a dealer.

As far as the gauge sweep goes, my reading of how that works (see post 108 above) is that it is driven by the cluster itself at key on. The fuel, battery and air pressure gauges are direct inputs - not through the ECM … Tach, Speedo, Oil Press, and Temp are ECM inputs.

Could be an ECM issue, but I need to explore the connector noted in my previous post first…

 

[BamaBus]

Is the red 'STOP' light due to the brake warning light?
There are two STOP messages, so is it possible that's why there is no tach and does not crank?

 

[ewo1]

Possibly a breakthrough (?)….

So, the other day we tested and retested the J1939 datalink forward and backward for continuity, and that all came back as expected - no broken wires in the cable.

Did a little more digging yesterday and came across a Cummins troubleshooting procedure related to the J1939 (procedure 019-165) which focuses on checking the datalink relative to the OEM harness to the ECM. (This is one of the two 60-pin harnesses to the ECM - the other being the “Engine” harness.) The procedure has you check:

1. The continuity of the J1939 + and - wires from the harness connector (pins 1 & 21) to their respective counterparts at the 9-pin diagnostic port (C &D). Checked fine…
2. Shorts to ground - i.e., pins 1 & 21 to chassis or engine block. These should show an open circuit, which Cummins defines as 100k ohms or greater… my result: 12.56k ohms …. Seems like a problem, maybe…OH OH !
3. Shorts between the OEM J1939 pins and all other pins in the OEM connector, with a short again defined as any reading less than 100k ohms. For reference, only 29 of the 60 slots in that connector have wires. Of these, I found 9 wires that had resistance readings relative to pins 1 & 21 (J1939 + & -) ranging from 12k to 20k ohms …

For reference the applicable pins are: 2, 18, 29, 32, 39, 45, 52, 53 and 55. Pins 2, 18 and 55 go to the multiplex module; 52 and 32 are related to the fan clutch; 29 and 39 are related to the J1587 network; 45 is the ECM power from the ignition switch; and 53 feeds the “wait to start” lamp on the instrument cluster. IF YOU COULD TEST THOSE PINS AGAIN BUT THIS TIME WITH THE FAR END DEVICES DISCONECCTED JUST TO MAKE SURE YOUR NOT READING ANY DEVICE IMPEDANCE VALUES.

This is where it gets interesting… with the exception of pin 45, all of those wires go through connector C701 which is one of 4 plug penetrations through the firewall just above the multiplexer…NOW YOUR GETTING SOMEWHERE! i BELIEVE ONE OF THE OTHER FORUM LINKS (post 101) I SENT YOU ELABORATE ABOUT THIS.....I think I also mentioned to look behind the multiplexer assembly.... Easiest and quickest way to test, get your hand on that cable going thru the firewall, move the wire bundle, I mean move it...and do some resistance test to see if your values change. write them down before and after so you don't get them mixed up.

Not certain if this is in fact the source of my comms problem…guessing that this could be a slow / intermittent short to ground, which might explain why I see the J1939 circuit resistance start low when I first measure it, then creep upwards…YES! YOUR THINKING IS ON THE RIGHT TRACK! Only way to really tell is to get into that connector and associated wiring. Could it also be a bad ECM, and if so, why just those pins?

Will leave it there for now and look a little more at the wiring diagrams, but appreciate any input / comments…

This is a really good observation/find !!!
My thoughts above in red..

 

[desrtdog]

Is the red 'STOP' light due to the brake warning light?
There are two STOP messages, so is it possible that's why there is no tach and does not crank?

From the multiplex ladder logic diagrams, it seems that the red STOP light is set when two conditions are met: (1) the service brake lamp switch input is active, and (2) the interlock feedback input is active…. Not sure what the second one is, but tracing the wiring schematics, it seems to be related to something called a “BVA PRESSURE SWITCH SIGNAL”…whatever that is…

Edit: actually wondering if that is related to the air system pressure… next time I am at the bus, I’ll charge the air tank from my shop compressor to see if that changes anything…

Another Edit: verified this evening that the red STOP indicator in my video was due to low air system pressure…so only issues are the COMM FAIL and ABS light…

 

[desrtdog]

Spent the last couple of days looking into the wire loom from the ECM OEM connector, pulling the PDU/multiplexer off the firewall, checking the connectors at the firewall (C701 in particular, but also C702 and C704) … pulled the apart and found everything to be in good condition - no evidence of any water intrusion.
Found nothing wrong with the harness on the engine side of the firewall.
When I had the connectors apart, I rechecked the OEM connector pin resistances that were previously showing “low” readings, to the J1939 pins in the connector (referenced in post #113 above) and they were showing an open circuit - like all of them > 3M ohms (whereas they were in the 12-20k ohm range). This tells me that the issue is on the cab side of the firewall…
Confirmed this by checking diagnostic port pins C/D to ground: 14.6k…
Reconnected C701/702/704; reinstalled the PDU; checked C/D resistances again (12.5k ohms), then while measuring, disconnected the instrument cluster connector A, and boom…resistance jumped to 128k ohms. (As I previously noted, the Cummins troubleshooting procedure calls for a resistance of > 100k to be classified as “open”.) Disconnected the B and C connectors as well (with A still disconnected) and no change in readings…
So, this seems to indicate a potential problem internal to the instrument cluster….which at first glance does not seem serviceable…

If anyone’s got a later model (2008+) Blue Bird, wondering if you could run an experiment to help me make sure this is not just another rabbit hole….. (1) disconnect your batteries, and (2) measure the resistance to ground of the J1939 + and - wires at your diagnostic port…

Still not obvious to me how this would throw the COMM FAIL message, but ????

 

[desrtdog]

Breakthrough???

Came across these videos …
Crank, no start - part 1
Crank, no start - part 2

The bus is essentially the same as mine, and the skymptoms in part 1 are also identical to what I am seeing: COMM FAIL at key on with ABS light on; crank, so start. He has a computer to see that the ECM does not appear to be communicating… also, when he checked the ABS module, he gets the same code that I am retrieving from onboard diagnostics - i.e., elated to the J939 retarder comms…The fix? New ECM!

Given that I have been backwards and forwards through the J1939, this seems like a good possibility at this point. Also, as I noted in previous posts, I had some potentially suspect resistance readings which I thought might be related to the instrument cluster, but I managed to get my hands on another cluster and verified the same readings from that one…so thinking that’s not the issue.

Going to try to get someone to run a scan on my ECM in place to confirm (bench test will require me to remove my A/C bracket and cost ~$400)…and in the meantime also look for a replacement…

More to come…


Oh yeah … forgot to mention that I did try the “gas soaked rag in the air intake” trick to see if the bus would start … it did after a little cranking and ran really rough for about 10 seconds, but stopped when the rag was removed…

 

[nikitis]

@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.