This is a side question to the purpose of this thread, but here is my question: If the battery voltage is say 12.6, 12.7, why is the control module voltage 11.9/12 and why? Does the ECM regulate the feed from the battery? I saw a similar thing when I was looking at some anomalies on my 5V feeds on my truck.
T87 Swaps
- Thread starter kidturbo
- Start date
In my case, that's probably correct voltage as the bench capture, is ecm and tcm running on a deep cycle battery with no charger connected. But typically I also see it reading .3-.5 under actual battery.
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Factory hubs should work fine to generate a nice clean pulse. But my idea of spin it with a belt, didn't pan out. So now plan is pick up a standard output shaft reluctor wheel, and mound it to this old RC aircraft starter motor. Then can test multiple sensor types against it easily.
I also tests my little digital sine wave generator against the T87 Allison speed input pins last night, and again it wouldn't recognize the signal. So how GM is using that same sensor in tailshaft of 15-`16 trucks, remains a mystery.
There is always going to be some voltage drop in the harness. Plus the ECMs voltage monitor is not likely as accurate or calibrated like a DVM will be. So if the tolerance of the components that make up the voltage meter in the modules is off a little bit that can change the reported readings on top of whatever voltage drop there might be. You also have to consider the electronic component tolerance stacking. Each individual component that makes up the circuit can be + or - 1% bit if you get a bunch of them that happen to be -1% that all add up to -10% in the end the voltage being measured can look like a half a volt or more off. The manufacturer isn't going to calibrate each ECM or module to match the source exactly like a meter manufacturer would
The ECM will also have internal regulators to drop the voltage to what the integrated circuits run at. Typically 5 volts for older stuff and 3.3 for the newer. The 5 volts to the sensors needs to be held tightly as some sensors will report false readings if the supply voltage is out of spec. But the 12 volt side may not be regulated
Ok, I discovered that rubber alone won't hold a 1lb steel ring onto an aluminum hub. It just missed my tv/monitor when it came outa balance.
However, superglue will hold rubber to steel, and rubber to aluminum, if used in abundance. And with a little luck on centering and balance, I've successfully welded aluminum to steel... At least good enough to capture some live sine wave data off our most common GM output shaft speed sensor.
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However, superglue will hold rubber to steel, and rubber to aluminum, if used in abundance. And with a little luck on centering and balance, I've successfully welded aluminum to steel... At least good enough to capture some live sine wave data off our most common GM output shaft speed sensor.
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No.. I didn't have one handy..
But I did have that starter from my Nitro RC Heli days laying around waiting for the right time to come of use again. It has some brush issues, but still spins up if ya wiggle the wires right. Then I picked up the recluctor ring tonight, and it just so happens to fit snug over the rubber bushing that held the starter rod for the heli's. Like it was meant to be.. However if ring moved any, came out of ballance slightly, it then became a one pound spinng steel ring with teeth, and inertia...
So figured one last Macgyver attempt, and superglued the crap out of it. Let it setup, and now is near perfection.. Spent the next hour running my 12v battery down capturing sensors on the snapon. Got some good details however. Like this sine wave from our pre-2017 VR rear speed sensor.
Next I captured the Arduino output, my PWM signal generator, and then connected the GM sensor to that VR to Hall converter I picked up a few weeks back. And wouldn't ya know it, that little sucker actually works as advertised. So next I return the scope, and then hook up our Analog speed sensor to this board, to the TCM, and spin up the wheel of fortune, and see if we have a winner.
I also plan to try these rear shaft sensosr with our T87 directly. But before I do, need to verify the pinout from end to end on the 2015-16. I'm almost thinking something tricky going on with the harness that year, because I'm fairly certain this analog VR sensor isn't going to like receiving a 9-12v input on one of it's 2 pins.
For now, here the analog to digit board capture receiving a sine wave from our common tailshaft, and being converter to a 0-5v Hall Effect output signal. Had to see it work on a scope with all the actual hardware before making the decision. It's most certainly the fix for the masses. And main reason I wanted to have real spinning reluctor on my desk. Can test all these different sensors for tolerances against our actual wheel found in most GM tailshafts since 90's.
What ya think of how this circuitry handles the conversion Jason? Raw analog input from our VR in green, converted 5v square wave out to our TCM in yellow.
I also plan to try these rear shaft sensosr with our T87 directly. But before I do, need to verify the pinout from end to end on the 2015-16. I'm almost thinking something tricky going on with the harness that year, because I'm fairly certain this analog VR sensor isn't going to like receiving a 9-12v input on one of it's 2 pins.
For now, here the analog to digit board capture receiving a sine wave from our common tailshaft, and being converter to a 0-5v Hall Effect output signal. Had to see it work on a scope with all the actual hardware before making the decision. It's most certainly the fix for the masses. And main reason I wanted to have real spinning reluctor on my desk. Can test all these different sensors for tolerances against our actual wheel found in most GM tailshafts since 90's.
What ya think of how this circuitry handles the conversion Jason? Raw analog input from our VR in green, converted 5v square wave out to our TCM in yellow.
Interesting little device you got there. One could probably use a zener diode to clip the sine wave and approximate a square wave.
I explored several options to do the same job including capacitor based designs, but those always follow the AC voltage. So at lower RPM they may only produce a 0.5v square wave. I noticed this TCM doesn't like a PWM signal which typically satisfies the older TCM's sensors, unless the duty cycle is right on 50%. Which is thn basically a 5v square wave format. This new IC chip keep things nice and square with the levels right at 5v. However the chip is very easily damaged if line voltage exceeds that.
My existing ADC to CANbus Gateway has 6 IO lines, so I can easily run the speed sensors though that one, but why task the main MPU with just converting a simple wave form and TX it as digital. Thinking merge this small circuit with my well regulated and existing 5v supply on the CANbus boards, and call it done.
If this T87 had some actually 5v Ref lines, we would be set with an off the shelf $20 board. But the only reference lines Ive nailed down so far, are 12v or 9v for the late model Hall sensors. But for now I'll pick up a couple more of these little boards for Beta Testing.
My existing ADC to CANbus Gateway has 6 IO lines, so I can easily run the speed sensors though that one, but why task the main MPU with just converting a simple wave form and TX it as digital. Thinking merge this small circuit with my well regulated and existing 5v supply on the CANbus boards, and call it done.
If this T87 had some actually 5v Ref lines, we would be set with an off the shelf $20 board. But the only reference lines Ive nailed down so far, are 12v or 9v for the late model Hall sensors. But for now I'll pick up a couple more of these little boards for Beta Testing.
That isn't a bad idea, as long as the ref voltage never exceeds a set ref value. Believe I measured 10v on our T87 Pin 7 and 8. But it could be a clean, inline, size of a dime fix to our who ran what for what year sensors.
However we still have to manipulate some canbus traffic, no matter what. So thinking we could power our canbus transceiver and our wave converter circuit off the same 9-12v regulated supply. If lose either component, you're kinda in the same limp mode. No PCM comms limp, or no speed sensor limp.
Speaking of speed sensors, I noticed I wasn't gettting a VSS value on my EFI T87 logs when I was feeding it Output Shaft pulses. I know for a fact the E35B uses CANbus based output shaft values to control the speed limitter, but which values creates our VSS I am not sure of.. Just found it strange it never posted a MPH.
However we still have to manipulate some canbus traffic, no matter what. So thinking we could power our canbus transceiver and our wave converter circuit off the same 9-12v regulated supply. If lose either component, you're kinda in the same limp mode. No PCM comms limp, or no speed sensor limp.
Speaking of speed sensors, I noticed I wasn't gettting a VSS value on my EFI T87 logs when I was feeding it Output Shaft pulses. I know for a fact the E35B uses CANbus based output shaft values to control the speed limitter, but which values creates our VSS I am not sure of.. Just found it strange it never posted a MPH.
Got the bench reluctor test rig all set. Can adjust the air gap easy enough. According to my math, spins 4600Rpm.
The converted patterns using the Max chip looks good on the scope. However was having issues with TCM accepting any of my emulated signals last night. Arduino or the VR to Hall. To many 110v to 5v inverters, and floating grounds in the mix. So wiring up everything to power off single 12v Batt only and try again.
Still can't believe it's all from scraps with just Super Glue holding it together.. Total investment, $1.50 if ya counf a full tube of glue.. lol
Source: https://youtu.be/e70WD7L_JOo?si=5aHqDj--Jgc_a3r9
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The converted patterns using the Max chip looks good on the scope. However was having issues with TCM accepting any of my emulated signals last night. Arduino or the VR to Hall. To many 110v to 5v inverters, and floating grounds in the mix. So wiring up everything to power off single 12v Batt only and try again.
Still can't believe it's all from scraps with just Super Glue holding it together.. Total investment, $1.50 if ya counf a full tube of glue.. lol
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Hey Kidturbo. Sorry was out of town down in florida and wasnt getting notifications for some reason. I just looked up 15-16 both and the wiring is exactly the same. Looks like i have some reading to do here to get caught up on what you have accomplished over the last 2 weeks.
@kidturbo after some investigation and looking at parts on the shelf from transfercases and looking up part numbers, I can tell you that 2008-2019 duramax at least all use the same vss reluctor wheel 40 tooth. Even the 2wd models have a 40 tooth reluctor in the tail housing of the transmission. Also looks like the turbine speed sensor changed in 2015.5-19 with the T87a-T87 to a #24276402, where 01-15 all had the same #29536408 sensor but still with the same specs to fit the same hole and mouting in the side of the allison case counting the same tooth count on the same part, so that would be a simple sensor swap and plug as the plugs are different. Im assuming that snesor change was due to the different between being ground referenced and 9v power referenced. The VSS from 07.5-19 looks to be a #19302667 (newest part number replaced a list of older numbers) so the same sensor should give the same pulse for the T87 as it does for the A50. From what little info i can get on the vss sensor from gm it appears that the 19302667 is capable of up to 18volt reference. Makes me curious though if the older vss could handle the same voltage range or only the newer updated ones will but are backwards compatible so they only offer the new one as a replacement for the older ground referenced use. In basic theory they are just a wire wrapped around a magnet, so with the correct number of windings, winding gauge, and magnet size the actual voltage reference vs ground reference shouldnt be a big issue assuming you put the correct polarity to the correct post. I am attaching the pinout for the difference between the 01-15 turbine speed sensor and 15.5-19 sensor and also the pinout for the vss that shows which pin is high and which is low.
Thank You @Baddiode that helps.. I'm with ya on the retro part for the VSS sensor, and reason needing the pinout before I connect those wires..
I have one good mid 2000's VSS with unknown part # on the bench. Pulled a couple from 4L80's in my buddies transmission pile couple summers back to use on my boat project. I machined the wheels down and mounted them on the driveshaft, connected to a T42 to track prop shaft speeds to actual boat speed. Worked perfectly, until I broke a driveshaft, which scuffed up one of the sensors face a bit.
So couple nights ago I'm playing with these 2 sensor on my 40 tooth bench wheel, and notice one of them isn't outputing a clean AC signal. Noticed the same with the SnapOn scope. The other one works perfectly with this little AC signal to DC Hall signal converter board. Watch a YouTube video on speed sensor testing, and of course you can Ohm test these or any wheel speed sensors to verify the resistance is wthin spec. Have one that is, and 1 that isn't..
950-2500ohm is what the video stated is our normal range. The good one is right at 1000ohm. While the bad one is showing couple million ohms. So next I pick up a couple weel speeds off my old F250 stuff, and both of those are in the million ohms range.. Neither of those will work with my AC/DC converter board either.. Now this has me worndering even more... Do I have 3 bad AC sensors, and 1 good AC sensor, or just 3 newer style DC sensor which have different ohms ratings than our old AC style???
If anyone has all the part numbers above, please ohm out the pins and lets compare. I'm gonna pick up a new style output VSS and turbine speed sensors also, to help sort this once an for all.. For now, I'm gonna go connect the ones that look bad to our T87 and see if any of them will produce a valid pulse the TCM will accept.
I have one good mid 2000's VSS with unknown part # on the bench. Pulled a couple from 4L80's in my buddies transmission pile couple summers back to use on my boat project. I machined the wheels down and mounted them on the driveshaft, connected to a T42 to track prop shaft speeds to actual boat speed. Worked perfectly, until I broke a driveshaft, which scuffed up one of the sensors face a bit.
So couple nights ago I'm playing with these 2 sensor on my 40 tooth bench wheel, and notice one of them isn't outputing a clean AC signal. Noticed the same with the SnapOn scope. The other one works perfectly with this little AC signal to DC Hall signal converter board. Watch a YouTube video on speed sensor testing, and of course you can Ohm test these or any wheel speed sensors to verify the resistance is wthin spec. Have one that is, and 1 that isn't..
950-2500ohm is what the video stated is our normal range. The good one is right at 1000ohm. While the bad one is showing couple million ohms. So next I pick up a couple weel speeds off my old F250 stuff, and both of those are in the million ohms range.. Neither of those will work with my AC/DC converter board either.. Now this has me worndering even more... Do I have 3 bad AC sensors, and 1 good AC sensor, or just 3 newer style DC sensor which have different ohms ratings than our old AC style???
If anyone has all the part numbers above, please ohm out the pins and lets compare. I'm gonna pick up a new style output VSS and turbine speed sensors also, to help sort this once an for all.. For now, I'm gonna go connect the ones that look bad to our T87 and see if any of them will produce a valid pulse the TCM will accept.
@pl_silverado see my last post above.
I believe you have all those different speed sensor in hand? If so, please ohm out the pins between and let us know the values.
I believe you have all those different speed sensor in hand? If so, please ohm out the pins between and let us know the values.
@kidturbo typically wheel speed sensors will range around 3-6 mega ohms because they normally use 2 or more small wound resistors sitting beside the manetic pole to keep them more compact but are more prone to heat fade and damage vs a single winding around the magnetic pole which will normally have a higher resistance and more robust against heat as well as offer higher amplitude with quicker discharge in faster pulse environments. So your wheel speed sensors are likely good but are just to faint of a signal would be my guess.