EBCM code: C0055 Symptom:5A
06-08-2017, 08:02 AM
#11
Staging Lane
Thread Starter
Awesome! I cant thank you enough for the info and the late night post, I could have waited till morning. :-)
I will get right on this and report back what I find. Reading this also got me thinking about a setting in the tune around speed limiting source being Calibration vs GMLAN. No idea if there is a relationship yet (I have not tested) but I'll check that too.
I will get right on this and report back what I find. Reading this also got me thinking about a setting in the tune around speed limiting source being Calibration vs GMLAN. No idea if there is a relationship yet (I have not tested) but I'll check that too.
06-18-2017, 07:46 AM
#12
Staging Lane
Thread Starter
The problem continues to evade me.
Additional list of things I've tried since the original post:
I will also note that in doing my circuit overlays I used taps to pierce the wires an inch or so from the connectors at the harness ends. I visually inspected the pins inside the connector and they look ok but electrically speaking that is not conclusive. Just dont know how else to do it.
I have studied the wiring diagrams from TCM to ECM to EBCM and am now fairly familiar with all the circuits at play here.
The tests I ran on 821/822 were in the driveway with the rear end jacked up. As such, I would not be able to throw the C0055 code and replicate the condition. I suppose I could run temporary wires into the cab with me and take a drive with the fluke strapped to my dash but even if I confirm the faulty signal at that time, what does it prove?
Additional list of things I've tried since the original post:
5.)Replaced ECM
6.)Replaced TCM
7.)Replaced EBCM
8.)Ran circuit overlay on circuits: 1827 (ECM to EBCM) and 6399 (TCM to ECM)
9.)Ran test procedures suggested by GR8TALK and they all produce expect results
10.)In the tune, tried every combination of VSS related configurations I could think of (WheelSpd, VehRepTOS, Serial, etc)
11.)In the tune, changed the ISS and OSS enable/disable flags in many combinations to see if there would change the behavior of this issue
12.)Flashed in the stock OS that came with the truck (I normally run 2 bar COS)
13.)Removed, cleaned and reinstalled ground on driver side engine block near knock sensor.
14.)Removed, cleaned and reinstalled battery ground (smaller lead going to front passenger frame area.)
15.)Removed, cleaned and reinstalled ground strap on driver side rear cylinder head to firewall.
16.) Found oil in the PRNDL connector so removed entirely, unpinned, cleaned thoroughly and then repined. (there is a RepTOS wire in that harness so figured it could be at play)
The only ground I did not re-do is the main battery ground to the passenger side cylinder head because I had recently redone that a few years ago and its in good shape. I suppose at this point it wouldn't hurt.6.)Replaced TCM
7.)Replaced EBCM
8.)Ran circuit overlay on circuits: 1827 (ECM to EBCM) and 6399 (TCM to ECM)
9.)Ran test procedures suggested by GR8TALK and they all produce expect results
10.)In the tune, tried every combination of VSS related configurations I could think of (WheelSpd, VehRepTOS, Serial, etc)
11.)In the tune, changed the ISS and OSS enable/disable flags in many combinations to see if there would change the behavior of this issue
12.)Flashed in the stock OS that came with the truck (I normally run 2 bar COS)
13.)Removed, cleaned and reinstalled ground on driver side engine block near knock sensor.
14.)Removed, cleaned and reinstalled battery ground (smaller lead going to front passenger frame area.)
15.)Removed, cleaned and reinstalled ground strap on driver side rear cylinder head to firewall.
16.) Found oil in the PRNDL connector so removed entirely, unpinned, cleaned thoroughly and then repined. (there is a RepTOS wire in that harness so figured it could be at play)
I will also note that in doing my circuit overlays I used taps to pierce the wires an inch or so from the connectors at the harness ends. I visually inspected the pins inside the connector and they look ok but electrically speaking that is not conclusive. Just dont know how else to do it.
I have studied the wiring diagrams from TCM to ECM to EBCM and am now fairly familiar with all the circuits at play here.
The tests I ran on 821/822 were in the driveway with the rear end jacked up. As such, I would not be able to throw the C0055 code and replicate the condition. I suppose I could run temporary wires into the cab with me and take a drive with the fluke strapped to my dash but even if I confirm the faulty signal at that time, what does it prove?
06-23-2017, 07:46 PM
#13
I still have this in my mind. One thought I have is this might be a input shaft to output shaft correlation issue. Something to the effect of a component slippage diagnostic. It only happens when stall speed is high and wheel speed is low. See how it comes back to life at 30ish mph. That has a direct correlation to the component slippage and iss to oss diagnostics. Ill post the DTC #s in a few. It might be something worth double checking.
06-23-2017, 09:19 PM
#14
Try this!! Look for a pid in the tcm called trans slip counter. This will indicate the # of slip occurrences 0,1,2. If you have anything other than 0 the trans is failing the component slip diagnostic. Get it to act up and watch that PID, Or just disable the p1870 slip diag under the trans diag >general. Set the temp to some unattainable value.
06-26-2017, 08:01 AM
#15
Staging Lane
Thread Starter
I think you are onto something but I dont think its P1870 specifically. I have changed the Enable Temp to 492 in the Trans Diag for P1870. I even tried setting all the various max and min slip settings in case they are used anywhere else, but no luck.
After that didn't fix it I set every single Trans DTC to "No Error Reported" essentially disabling all DTCs
In the Speedo calibration tab I've tried some more settings for the Wheel Speed Sensor Pulse Average and Max period but no luck yet. I have lots more iterations to try there.
The other test I did was to disconnect the front left and right wheel speed sensors and drove the truck to make it act up and see if somehow the GMLAN was stealing the signal from those sensors but again the speed signal from the transmission was steady and uninterrupted.
After that didn't fix it I set every single Trans DTC to "No Error Reported" essentially disabling all DTCs
In the Speedo calibration tab I've tried some more settings for the Wheel Speed Sensor Pulse Average and Max period but no luck yet. I have lots more iterations to try there.
The other test I did was to disconnect the front left and right wheel speed sensors and drove the truck to make it act up and see if somehow the GMLAN was stealing the signal from those sensors but again the speed signal from the transmission was steady and uninterrupted.
07-06-2017, 07:28 AM
#16
Staging Lane
Thread Starter
As a long shot, I opened a support ticket with HPTuners to see if they could help. The ticket was routed to an engineer who reported no software issue to be found and that "Its recommended that this get posted tot he forum for tuning advice."
Based on all the PD I've done to this point, its clear the issues is the 0 mph speed signal being sent from the ECM to the EBCM on a hard launch (high stall speed). I am convinced its not a wiring/grounding issue since the problem is so consistent and only can be regenerated in that very specific scenario. I am just not convinced that there isn't some slip related condition being detected in the ECM causing it to report the 0 speed for that period of time. The only flaw in that logic is that as reported in a previous post, if I stay on the pedal steady after hard launch, the speed stays zero for as long as I can hold the pedal. In other words I can accelerate hard and keep the pedal held through 3 gears while the EBCM continues to see 0mph from the rear wheels. This entire time, everything else works flawlessly with no ECM or TCM codes.
Would there be any good places to add additional ground wires for testing? From what I understand the circuit 1827 switches ground to make up the signal.
Based on all the PD I've done to this point, its clear the issues is the 0 mph speed signal being sent from the ECM to the EBCM on a hard launch (high stall speed). I am convinced its not a wiring/grounding issue since the problem is so consistent and only can be regenerated in that very specific scenario. I am just not convinced that there isn't some slip related condition being detected in the ECM causing it to report the 0 speed for that period of time. The only flaw in that logic is that as reported in a previous post, if I stay on the pedal steady after hard launch, the speed stays zero for as long as I can hold the pedal. In other words I can accelerate hard and keep the pedal held through 3 gears while the EBCM continues to see 0mph from the rear wheels. This entire time, everything else works flawlessly with no ECM or TCM codes.
Would there be any good places to add additional ground wires for testing? From what I understand the circuit 1827 switches ground to make up the signal.
07-06-2017, 10:59 AM
#17
Another thing I have found is that the EBCM on the van system does not have the symptom bite you are getting. The 5A is specific to the truck. Probably due to not having an iss from the factory. I wonder if a van EBCM would bolt to the BPMV? Or if you could flash your EBCM to a van configuration?
07-06-2017, 12:38 PM
#18
Staging Lane
Thread Starter
It looks like the van EBCM has a different connection harness as well. Not sure if it would bolt to the BPMV but I'd also need some sort of conversion harness just to test the theory.
I wonder if there is a better OS choice for the 4L80E when going into a truck. I suppose I could blindly try some T42's from the tune repository, but not sure if it could do any damage?
I wonder if there is a better OS choice for the 4L80E when going into a truck. I suppose I could blindly try some T42's from the tune repository, but not sure if it could do any damage?
08-30-2017, 07:14 AM
#20
Staging Lane
Thread Starter
@GR8TALK, I cant thank you enough for all the help so far. I have not come up with any new ideas but have tried some wild stuff in the trans tune in attempt to observe different behavior but still no luck. Just curious if you (or anyone else for that matter) had any more ideas?
I posted over on HPTuners forum and also opened a support ticket in case there were any ideas but so far no bites. Support tells me its not a software issue so they cant help. I am still searching desperately for that one guy out there who has at least seen my exact issue. Since I have still not found that person I have to believe I am missing something stupid, but who knows.
I posted over on HPTuners forum and also opened a support ticket in case there were any ideas but so far no bites. Support tells me its not a software issue so they cant help. I am still searching desperately for that one guy out there who has at least seen my exact issue. Since I have still not found that person I have to believe I am missing something stupid, but who knows.