73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: MuddiGGEr25 on June 02, 2017, 05:44:38 pm
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I have 1.10V coming in on the pink wire with black stripe, should there be 5V or 12V? im only getting reverse and 1st gear, and when i let off the throttle at 30mph it just drops back down to idle. im sure if i manually put the trans linkage into L it would hold onto 1st gear, but im trying to get it to shift.
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Did you check for DTC's? What is the serial data displaying? Did you check the fuse for VSS buffer? The voltage output from the sensor will vary based on speed output.
On a side note, you haven't provided enough information and if i'm not mistaken you have more than one thread going on which makes it hard to follow exactly what it is you're doing.
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Did you check for DTC's? What is the serial data displaying? Did you check the fuse for VSS buffer? The voltage output from the sensor will vary based on speed output.
On a side note, you haven't provided enough information and if i'm not mistaken you have more than one thread going on which makes it hard to follow exactly what it is you're doing.
Its the 1995 454TBI/4L80E that i swapped into the 1988 V20 suburban. I dont have an ALDL port to wire up, nor do i have the check engine light wired up.
Im not talking about voltage output, i was asking about the input voltage, but i traced the wires and they both go directly to the PCM, so im assuming its the correct input from the computer.
I have absolutely no idea where to find the VSS buffer fuse since i got the whole harness and the wires literally go straight from the VSS on the back of the trans (right before the Tcase adapter) up to the PCM
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At this point, i am trying to make sure im not missing any connections. the 4L80e does not have a vac line connection that i could see, so im assuming it doesnt have one. its perfectly possible that i did not power one of the + wires or missed a connection. but from what i can tell the TBI/4L80E in 1994/1995 should be able to standalone without any input from the body/original dash
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So you have the whole harness but don't have the data link connector or VSS buffer and warning lamps hooked up? It sounds like you need to hook everything up before you start troubleshooting.
Also if it's a 4WD the VSS is on the transfer case not the transmission. I'm not sure what you are probing because the VSS does not send it's signal directly to the ECM. The input speed sensor is on the transmission.
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do these help any?
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and this
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also are you sure its 1st gear and not 2nd? 2nd gear would indicate limp mode. want to say when i did my motor swap without sensors or a computer connected i had 1st and maybe 2nd. we drove it around the farm so i want to say it was second
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I just woke up and I'll print off all those papers too and get my CEL connected. I'll just jump the terminals right at the PCM for now just to get the codes. Also I have attached a link that claims the 1991 to 1996 should have theVSS on the drivers rear of the transmission and 1997+ 4wd should have it on the tcase, and I have seen several forums mention the same for 1992 and 1993 in the many searches I have done. That's why I didn't think I had a separate VSS, because the only connector I could find on TCASE that it was attached to was a connector for the 4wd indicator lamp
http://www.novak-adapt.com/knowledge/transmissions/automatic/4l80e
Scroll down to the Speed Sensing section
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you have to think about the 95+ 4x4 is in stock form it should be drivers side drop. my 91 crew cab is passengers side drop so my vss is on the passengers side
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Yes this was originally a drivers side drop but im using my NP208 so passenger side drop. but i just crawled under and realized the ISS was just coated heavy with di-eletric grease to keep it from rusting (courtesy of the seller) so i then realized the connector i extended was actually for the ISS, so i just wrapped up my "extension" and plugged it into there, and now i have to figure out where the wires are for the OSS on the back top corner of the trans (i am sure its the OSS as its in the location shown in all the pictures for where it should be, and the connector is the same)
I can get a pigtail from the parts store for the OSS monday or tuesday, if they dont have one in the HELP section, but first i need to find out if the "female connector" coming out of the wire loom on the drivers side is supposed to connect to an extension down to the OSS or maybe the transfer case.
I have also read on a couple forums that if i use 4x4lo im going to need to send a signal to the PCM so it shifts correctly? but i dont have a Speed sensor on the transfer case so i dont know if thats even going to matter, and i dont plan on using it in 4lo anyway
I could theoretically just run a new wire pair up to the PCM to the OSS myself.
(ISS= Input speed sensor)
OSS = Output speed sensor
I can get to 30MPH and its wound out pretty good but not overkill. im gonna hook up the tach tonight or tomorrow and see what RPM im at at 25-30MPH, then i will know for sure what gear im in.
If it helps at all, if anyone has driven a TH400 with the vac line unhooked and you try and drive up to 30ish it doesnt shift and the engine will drop back down to idle if it hasnt grabbed 2nd, thats exactly what it seems like here too
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do these help any?
So im looking at pin C15, transmission output speed signal. its a brown wire, single wire, im gonna crawl under there again here later, but i think i saw it earlier, but the speed sensor has 2 wires, just like the input speed sensor ( from what ive been reading, they are both the same physical sensor, the only difference is the location in the transmission.
I wanted to try and manually shift into L, 2, 3 but my shift arm was only long enough to read 3rd gear, so i cant try that unless i put the axle on jack stands since its limited slip, which i might actually give a shot tomorrow, just to see what happens.
I need to find out what color the 2nd wire is for the rear sensor, and i think im just going to run a new set down if i cant figure out which connector its supposed to be
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if you manually put it in 1st you should be able to up shift it
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Hey guys, I think I found the pair of wires that is for the rear or output speed sensor after reading a lot if various forums. I am going to try and upload a screenshot of one of them. He said he has been using it like this for a while now and no issues.
From what I can tell from my research, up until a certain year, seemingly 1996 when they switched to obd2, there were 3 speed sensors: input speed sensor towards the front, output speed sensor to the rear, and a vehicle speed sensor on the transfer case on 4x4 models to let the computer know when it was in 4lo to change to a different mapping table. 4l60e omitted the input speed sensor from what I have gathered from people doing swaps. The ISS and OSS both go to the TCM or in my case the PCM the vehicle speed sensor on the tcase (4x4 only) goes up to the DRAC and buffer and gets converted for the speedometer and cruise control. Since I am using neither of those for now I won't be needing the buffer or 3rd speed sensor.
I am going to have the local parts store request one of the pigtails today and I'll be putting it on Friday and see if it will shift correctly.
My backup plan is to extend my spare shift linkage arm from a 4l60e by about 3" and put it in there so I can manually up shift if my pcm won't shift with the 2 speed sensors
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Here are the screen shots from one of the forums
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I may have missed something in the threads, but my 1991 has 3 sensors!!! First there is an Input Speed Sensor (ISS) on the LH side of the transmission, kind of above the shift linkage. Second there is an Output Speed Sensor (OSS) that is above the large electrical connector. Finally, there is the Vehicle Speed Sensor (VSS) that is on the transfer case. I have no idea what the OSS does, as more modern vehicles do not use it. Perhaps it is used in our vehicles to tell the difference between low and high range in the transfer case. More modern vehicles use a simple input from the transfer case to tell when it is in low range.
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I may have missed something in the threads, but my 1991 has 3 sensors!!! First there is an Input Speed Sensor (ISS) on the LH side of the transmission, kind of above the shift linkage. Second there is an Output Speed Sensor (OSS) that is above the large electrical connector. Finally, there is the Vehicle Speed Sensor (VSS) that is on the transfer case. I have no idea what the OSS does, as more modern vehicles do not use it. Perhaps it is used in our vehicles to tell the difference between low and high range in the transfer case. More modern vehicles use a simple input from the transfer case to tell when it is in low range.
What I have discovered according to others is the opposite of what you just said. The output speed sensor in conjuction with the input speed sensor let's the transmission Determine shift points and if there is slippage of any components. The VSS like I said before puts out a different signal (DC) and has to go to the buffer before being sent to the PCM or TCM (depending on model) and then also up to the speedometer.
Modern versions of the 4l80E in 4x4 models omit the output speed sensor and rely on the transfer case signal for both speedometer and shifting.
The tcase sensor on those equipped with 3 sensors only tells the ECM/TCM how to respond when in 4lo. Many people have had 4lo shifting problems but 4hi and 2hi work fine and found out it was the speed sensor on the transfer case. I also read several that could only shift properly in 4lo because the output speed sensor had failed and when shifted to 4lo the computer isn't using the output speed sensor and instead uses the vehicle speed sensor in the tcase and uses a different map in the programming as well.
This ONLY seems to apply to vehicles equipped with the 3 individual sensors on 4x4 4l80E vehicles. 2wd and modern ones omit the OSS
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Interesting! I knew there was something funky with the 3 sensors, but didn't know exactly how it interpreted it. I'm working on a 6.0L LQ4 Conversion on my 1991 V3500, but I am having to cap the OSS electrical connector in my 4L80e and extend the VSS wiring to my transfer case. Then I will have to figure out some sort of microswitch for the low range signal off of my transfer case linkage or something, as the NP205 doesn't have a switch for that.
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from my memory the sensor that goes to the drac box then to the speedo and ecm is on the output shaft (aka TOSS Transmission output speed sensor). in 4lo the vss takes over, this way if your in 4low your speedo is still reading the correct speed. the way the stock pcm works is the vss (toss) goes to the dracs box from there it changes the pulses from 40 pulses to 2k for the ecm, 4k for cruise control and 128k for abs.
the TISS is mainly for the Torque convector lockup
also check this out
http://www.trucktransdiag.com/downloads/4l80e-tech-info.pdf
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All I know is what I have read on various forums. But only seems to be applicable to 1991 to 1995 4l80E 4x4 bUT not all of them.
If the speedo was running off the rear transmisson speed sensor it would be wrong when in 4lo. Think about it. The mechanical speedo runs off the tcase so it's always correct in both hi and lo ranges. It would make more sense for the DRAC, speedo, and cruise control to all run off that sensor on the tcase.
The output shaft of the trans will be turning the same RPM in 4lo or 4hi but the range selected will cause the speed to be either be correct or way off because of the speed of the driveshafts.
I can also verify that the TISS and TOSS are the same part numbers and put out an AC waveform. I cannot verify that the transfercase puts out a DC signal as I have not tested it. But I do know for a fact it is an entirely different sensor and part number.
Most schematics only show the TISS and the VSs on the tcase with the newer programming and chips
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Ok
Here is a good website for 4l80e pinouts and information
http://www.michaelrenz.com/4l80e/
I have the DRAC right on my pcm and my pcm says 16197427, but the 2 wires ( dk green with black stripe, purple with white stripe) That would plug into the rear sensor on the transmission are not listed at the PCM on any wiring diagrams but yet I omhed the wires and they go right into the ECM on the red connector at pins E4 and E7 and E7 is listed as unused. But the dk green black stripe goes into E7 and purple white stripe goes to E4
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i did leave the important part out about 4lo in my past post. (in 4lo the vss takes over, this way if your in 4low your speedo is still reading the correct speed)
1991 to 1993 four wheel drive trucks use two output speed sensors, one in the rear of the
transmission case, and one in the transfer case. When the transfer case is in 2WD or 4W HI, the
signal from both speed sensors should be the same. The PCM/TCM internal buffer signal is
constantly being compared to the external buffer signal on circuit 437, (Speedometer contained
DRAC on 1991 K trucks only). Once the transfer case is shifted to 4W LO, the output shaft speed
sensor signal is now higher than the transfer case output speed sensor. At this time the PCM/TCM
will adjust for shift timing and speedometer accuracy. It is the output shaft speed sensor that is
responsible for shifting the transmission in 2WD and 4W HI. In 4W LO, it is the transfer case output
speed sensor that shifts the transmission, (Refer to Figure 57
1994 to 1995 K trucks with 4L80E transmission, eliminated the function of the output shaft
speed sensor in the rear of the transmission case. However due to engineering problems, the
speed sensor was left in the hole just to keep oil from spraying out, IT HAD NO FUNCTION
and no wire connector.
The speed sensor in the transfer case became the TOSS and the VSS, (Refer to Figure 61).
Shift timing adjustments and speedometer accuracy in 4W LO range was accomplished
through the use of a 4WD LO Switch in the transfer case in earlier vehicles and a Transfer
Case Control Module (TCCM) in the Later 4x4 vehicles. Both 1994 to 1995 K and 1993 to
1994 T trucks with 4L60E transmission evolved in a similar way. Beginning with K trucks
in 1996 and T trucks in 1995, the DRAC was eliminated. All VSS buffering now took
place inside the Vehicle Control Module (VCM) just like the passenger cars did since the
4L60E began use in them for the 1994 model year.
http://shop.ukrtrans.biz/wp-content/uploads/catalogs/4L60E_80E_CODE_BOOK.pdf
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might have miss understood the role of the toss. it might just be there to see if the vehicle is in hi or low. if the numbers match the ecm knows its in hi if they dont match the ecm knows its in lo
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· The Input Speed Sensor signal is compared to the Output Speed Sensor, by the computer, to
calculate gear ratio. A faulty Input Speed Sensor could cause gear ratio error codes to be
stored.
· The Input Speed Sensor signal is compared to the engine rpm signal, by the computer, to
calculate TCC slip. A faulty Input Speed Sensor could cause TCC slip codes to be stored.
· Some 4L80E equipped vehicles will have no output RPM displayed on the scan tool when
there is no input RPM signal. The transmission will react as if it lost the VSS signal, no
upshift.
· Input Speed Sensor resistance is 1260 to 1540 ohms.
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TOSS & VSS ELECTRICAL VALUE CHART
MPH AC VOLTS HERTZ
10 4 265
20 7 530
30 10 800
40 13 1080
50 15 1300
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I am going to connect to the TOSS because it goes right up to the PCM red connector. And I cannot find an accurate pinout for my truck donor... 1995 K2500 7.4L 4L80E. But I have a DRAC with the letters PYH and the harness didn't have any connections for it, but it's there nonetheless. But I have looked at many many 16197427 PCM wiring diagrams and none of them are correct. There are several pins that are supposed to be not used and I've got wires going into them or not the correct signal accordin to the diagram or the diagram only says 4.3, 5.0 and 5.7 I can't find anything really for the 7.4l. And what I do find is with people with the 13PSI tbi and I have the 32PSI tbi system so that seems to screw up my luck too
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this is from hatzie
17021.24 GM STG Hydramatic 4L80-E Transmission Electrical Supplement (http://www.mediafire.com/download/2o21d84ygmh6sdb/GM_STG_17021_24_Hydramatic_4L80E_TRANSMISSION_Electrical_Supplement.pdf)
i cant look at it right now due to a firewall but maybe it can help you out
heres a good list of all the PDFs
http://67-72chevytrucks.com/vboard/showpost.php?p=5621043&postcount=1
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according to that one thing i posted there was no TOSS in 95
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Here, I screenshot the pages that had info regarding the TOSS and it's role in shifting. I don't know what year this book is referring to but it says the TOSS is sent to the PCM unbuffered and the tcase sensor is sent to the DRAC. Which would lone up with some of the vehicle combos I have read about. I will know for sure in about an hour or so when I connect the VOSS and find out if it actually sends a signal to the PCM. I cannot pull it out because I am at a campground and cannot risk to spill ATF.
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Quick update. Got the VOSS wired up and it did do a 1st to 2nd shift. I got up to 58mph which should be 3rd but it sounded pretty wound out. But I don't have the tach hooked up till later today
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Another quick update. If I reset the computer I definitely get a 1-2 shift. But I think it goes into protect mode aka 2nd gear only after that. It doesn't shift out of first until 30mph, but it's very noticable lol. Anyways I have to look into relocating the fuel pump because it vapor locked at the gas station bc I mounted it pretty close to the heater core hoses. I let it cool off for about an hour and it started right back up. But my FPR gasket is leaking so I gotta go get a kit for that first bc it leaked and caught on fire..... at the gas station.... at the pump.... not a fun day. Anyway after that I'm gonna find the wires in the harness that are supposed to go to the ALDL connector and the CEL and get my codes now. I know I'm gonna get the 2 codes for the oxygen sensors since my 6.2l exhaust doesn't have them and I don't have the 150 to get bungs and sensors right now. We have enough gas ( maybe) to get to our destination so I can find work.
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whats odd is i have a pcm from a i think 93 k3500 with a 6.5 and 4l80e i was planning on using it for my cummins but never got around to working with it. i dont know if anything from that could help you or not
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also since your attachments talk about "code ??" im going to assume thats an obd1 system obd2 afaik would have a letter in front of it. so we know its no newer than 96. and since they talk about toss and from the other data we have i would think that means its no newer than 93. so it has a date of 91-93
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Right now I'm in the process of relocating the fuel pump and filter so it won't get so warm. And hooking up the tachometer so I can see my RPM while driving it
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Ok I haven't relocated the fuel pump just yet as its now 93F in the shade, but I did switch the wires on the TOSS just to see if it will act any different. I drove around the park and 3000rpm at around 24 to 27mph, not sure if my speedo is right or not. Gonna get up to 55mph here in about 10 minutes
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you said your trans and wire came from a 95 3500 with a 7.4? how does it have a toss? does it have the 3 plugs or just 2? (minus the main plug)
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It has 4 plugs, it was pulled from a running and driving k2500, the only issue they had was trans fluid leaking from a poor weld job on the tcase adapter. I mean it's possible it was a 2wd that was rebuilt and made into a 4x4 but it has the 2 larger plugs and 2 speed sensors on it just like a 2wd transmission.
I got 4200rpm at 55mph and it shifts from 1st to 2nd if I leave the PCM unplugged for a bit before a test drive,
otherwise it appears to start in 2nd gear ( fail safe mode if the PCM is left powered on) I got to 62mph and my rpm were about 5000.
My shift arm is just long enough to get to 2nd gear on the transmission, and I can make it stay in 2nd if I put the shifter there, but if I put it in 3rd or OD it will only engage 2nd when I press the gas (after the rpms come up to the proper speed)
Since I am on a pretty tight budget and time frame, will either of the following options work: can I toggle the 2-3 solenoid with a toggle switch on the dash to force 3rd gear? Of I don't have 4th or lockup it's not the end of the world but we have to be out of here and on our way to missouri before the park closes tomorrow. Or if I extend that 4l60e shift linkage so that I can reach the position for 1/L and shift up each gear one at a time. Will that work even if the PCM is not getting the correct VSS?
I only have my smartphone do trying to read wiring diagrams on here takes forever but I'm working on a way to get codes. But in any case I'm sure it's going into limp mode
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I lied, it's the main plug, then a front speed sensor, a rear speed sensor and the 2 plugs on the PRNDL box/controller
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ok so you dont have a toss just a tiss and vss? other signals you have to have is the tps and rpms, do you have those?
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No I have a TOSS AND a TISS. I am supposed to have a np241c on the back of the 4l80E but it's just my np208 with a mechanical speedo.
The 241c that was in the donor truck had the VSS. But I couldnt afford to buy it and then try to convert it to passenger side drop. I will attach a link to some pics on my Facebook that I will make public
And my TOSS obviously is making some kind of signal to the PCM because without it I cannot get into 1st gear no matter what
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you need the vss or something to convert a mechanical cable to electric signal. ive looked into a few TCUs and each one requires the vss, i think the reason 4l60e doesnt require a toss is cause they didnt come out till 94 and 94 is when the 4l80e also lost theirs. i dont think the toss sends the same signal as the vss. (but that wasnt true after doing research) and like i stated before the ecm uses the VSS signal for everything and compares the rpms to the TOSS to know if its in 4lo or not. the TISS and TOSS work together to see how much slip the trans have. if it senses slip it will kick into limp mode
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it does appear the vss and toss have the same output.
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im almost certain i could shift 1st and 2nd without any computer hooked up. but anyway, your wire harness and trans came from the same truck 95. youre saying it has a toss so this contradicts whats in that one book about the toss being eliminated in 94. if you have the plug for a tiss, toss and vss then i would think you have to have each one of those sensors working. if you have the wire harness for a tiss and vss then you could in theory plug the vss plug into the toss and get good results.
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https://m.facebook.com/story.php?story_fbid=10211259527576774&id=1016864859
There is all my connections. I do not know if I have the rear speed sensor connected to the VSs wiring or the toss wiring. I spliced the rear speed sensor into the only wiring close enough to be connected ( again due to budget constraints I could not purchase the connector)
What I'm trying to figure out is If I can wire a manual toggle switch on my dash ( only to get us to our destination then purchase a scan tool that can read the data stream) that will manually activate the 2-3 shift solenoid and get it into 3rd gear assuming all other factors stay the same from 2nd gear into 3rd. If I can get 3rd I can roll down the highway without screaming.
Obviously flip the switch off when needing to stop and have the gear selector on 3
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i know its not what your asking but i got a black box cost 230 from jakes performance
http://shop.jakesperformance.com/Manual-Control-Box-for-4L80E-JP-MCB.htm
so its simple to wire up and requires no sensors and it turns the trans into full manual. again i know its not what you were asking but its possible to make the trans work and i think ive read online that you could make your own
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I know I saw that, but I don't have that kind of cash or time to wait for delivery atm. I will be out if work due to my back for at least 2 or 3 months while I go to physical therapy and to the chiropractor. Pills are only doing so much good for me :(
From what I can tell from reading diagnostic papers for the 4l80e. Under normal circumstances, when the TCM or pcm goes from 2nd to 3rd it just activates the 2-3 solenoid and adjusts line pressure according to load or TPS value. All other signals appear to remain the same from 2 to 3 except when at WOT or other programmed variables.
I'm gonna try it tomorrow and hope for the best.
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good luck, im interested in understanding the 4l80e also
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Well I learned that the solenoids are controlled via grounding at the PCM. So putting 12V+ would have done no good.. but that being said I checked my ign+ to the transmission and it was good. I tried to ground the 2-3 solenoid but no luck, it wouldn't click. So then I tried to ground the 1-2 solenoid and voila it clicks. So I checked voltage passing through the 1-2 solenoid and got nearly fully ignition voltage reading (about 11.8 to 11.9 bc my batteries are a bit low + resistance of the solenoid.) Next I checked the voltage coming out of the 2-3 solenoid and it reads 1.80V so I'm pretty sure that solenoid is junk.
I would have thought of it sooner but the video of the truck I saw before the engine was dismounted was only 30 seconds long and it just drove around the property. Probably never over 30mph. And he told me no guarantees on the transmission.
In any case I might leave the toggle connected so I can manually get into 1st gear if I need it, otherwise 2nd will be good enough for the moment.
We had a change of plans with family memyers having surgery and cancer not going into remission so we are going 50 miles north to a campground for about 430/mo until all that is sorted out. I'll get some work soon and order a solenoid and figure out how to change it without anyone figuring out I'm dropping the pan at a campground lol.
Next I can figure out if the TOSS is giving a good signal to the PCM or not ha.
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Update: took 54 hours to go 63 miles because top speed was 35mph and the fuel pump would overheat bc if poor placement on my part. Then 30 minute cool down every 2-3 miles.
Then 6 miles away from our destination I think the tcase went kaboom. There was a few loud clunks then we stopped moving. Then I crawled under and moved the tcase to manual nuetral and the transmission too and it was grinding for the first couple miles then no grinding. If I start it and put it in gear you can hear the transmission start winding up but no movement. And i can not disengage the rear shaft when I try to manually shift into N on the tcase. The front shaft releases in 2hi but in the N position it still seems to be hanging on to the driveshaft