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Discussion Starter #1
I have a oil leak which I think is coming from the engine speed sensor that mounts where a distributor would be if it were gas. This is to the left of the OPS which I have already changed out cause of lift pump inop. What I would like it to confirm this is the speed sensor and where to get one and a part number. I have searched but no luck so far. I also have a SES light on when engine is cold. <<<NO CODES>>> Light goes out when engine is warm and as rpms go up. this effects my lockup convertor so as not to work when SES is on. does anyone know if this sensor could also cause this problem?


My truck is a 1992 GMC 6.5LTD 4L80E Auto 4x4


Thanks to all...


[EDITED BY ME, ADDED TEXT BELOW]


To help this I have found some info for all with same problem with SES light and trans shifting...
Constant or Intermittent MIL ON, No DTC's Set

Number: 93-33-6E
Section: 6E
Date: OCT. 1992
Corporate Bulletin No.: 177138R
ASE No.: A6
Subject:
CONSTANT OR INTERMITTENT ENGINE LIGHT
Model and Year:
1991-93 C/K, R/V, P AND G TRUCKS
TRANSMISSION APPLICATIONS:
1991-1993 HYDRA-MATIC
4L80-E/4L80-EHD (MT1)
TRANSMISSION MODELS:
All
SUBJECT:
Constant or Intermittent Check Engine Light, Line Pressure and TCC Fluctuation (No Codes Stored)
VEHICLE APPLICATIONS:
C, K, R, V, P Trucks, G-Van Equipped with LL4 6.2 Diesel or L65 6.5 Turbo Diesel
CONDITION:
Some 1991-1993 trucks equipped with the L65 6.5 Turbo Diesel or the LL4 6.2 Diesel and 4L80-E/4L80-EHD exhibit a constant or intermittent check engine light with the engine running and no codes stored.
CAUSE:
The 4L80-E/4L80-EHD use an engine speed sensor and if failure occurs a code will not be stored. Code 12 will be present with the engine running and the ALDL grounded. The electronic transmission control section of the 1991, 1992 and 1993 service manuals does not acknowledge the use of an engine speed sensor or code 12 for the L65 (6.5 turbo) or the LL4 (6.2) electronic transmission applications.
CORRECTION:
Check for proper engine speed sensor operation as follows:
1991 and 1992 Vehicles
For diagnosis, use the code 12 chart from the LH6 Diesel Emission Section of the 1991 or 1992 Service Manual (Pages 6E2-22 and 6E2-23). When following the trouble tree, substitute TCM PIN D7 for ECM PIN C1 and TCM PIN D6 for ECM PIN A8.
1993 Vehicles
For diagnosis, use the code 12 chart from the LH6 Diesel Emission Section of the 1993 Service Manual (Pages 6E2-22 and 6E2-23 for the G Van, Pages 6E2-32 and 6E2-33 for the C and K vehicles). When following the trouble tree, substitute TCM PIN D7 for PCM PIN F5 and TCM PIN D6 for PCM PIN F4.


Edited by: taz63nj2000
 

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Discussion Starter #2
I found part number and it is #7849305

Item is called "Oil Pump ASM". Took the guy a few trys at the local GM dealer to find it cause in the repair "GM" book it is called "Engine Speed Sensor".
So here is another part number to add to the list.

This is NOT used on Manual Transmisions!!!
It is only for Auto trans to give TCM an RPM signal to control shifts, Tourqe convertor lockup and fluid pressure in trans.
Alot of problems can be caused by this sensor being bad!!!
 

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I looked this up in the chilton's book and it says that the vss (vehicle speed sensor) sends a pulsing volt signal to the ECM which the ECM converts to vehicle speed. this sensor mainly controls the TCC( torque converter clutch) and cruise control. book says it's mounted on the transmission at the end of a speedometer cable.
 

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Discussion Starter #4
HI Quantum,


This is NOT the VSS it is the ESS.


The VSS is in the trans and does control the speedo and other items including the cruise control.


The ESS is a sensor that was used in 1992/1993 year trucks/vans on 6.5LTD with auto 4L80E trans. It sends a 4 pulse per 1 cam revolution to the TCM as a RPM reference signal used to control line pressure, shift point and firmness, and TCC lockup. This sensor is mounted on top of the oil pump drive mech on the rear center of engine.


This info is right from GM corp. and the tech service bulletin for this issue is listed at the top of this post for reference...


Thanks for the reply but this is not the VSS and that is the problem I was having locating this part. Most retailers and some dealers were giving me info and numbers for the VSS and I looked at picture of those sensors and they looked nothing like what I needed. I did some major digging to finally locate the correct part number and parts.


I listed the part number here so others can locate this quicker that I did...


Thanks.
 

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Hey I'm new to this forum, but not new to GM diesels, Thanks for the part # info on the ESS, taz63nj200, as I may need one, sometime. What I was thinking was since the ecm knows the rpm of the engine. Is there some way to get a signal for a tachometer? I have a 91 Sub, and there was no provision for a tach,Thanks, Artie
 

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My '93 has a tachometer. It gets its reading from the alternator. I discovered this when the fuseable link from the alternator was broken.
 

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The ESS was available on the pump-drive, as well as the combo vacuum pump\drive assembly.


Being driven off the camshaft, the output is 4 per crank revolution, same as a gasser ignition distributor.


Most aftermarket tach vendors offer compatible interfaces, either separately or as a tach option.


Requirement is a buffer that converts 0.5 - 5v ac signal to +12v square wave, 0 - 350hz


(4 x 5000rpm/60 =333.33hz) Edited by: gmctd
 

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Thanks for the part # taz63nj2000.
 

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From Rock Auto:ACDELCO Part # 21597 {#07849305, 7849305} GM Original Equipment $246 OUCH!
 

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Holy old thread batman!

Anywho, for new comers, I replaced mine in my 93 a couple months ago. The speed sensor needed from the first post applies to 92 and 93 years only since it feeds the TCU and has a sensor on top (94+ do not). In 94 when they made an ECU, it did the speed controlling through I believe the alternator.

Read my post about it. And copy pasted relevant info below;

Just wanted to follow up. Received the RPM sensor today, cheapest place was amazon at ~$225. Dealer wanted $500+. For what its worth, if anyone in the future reads this by some chance, the ACDelco part no. is 215-97, but I received one with GM markings and part no. 7841996, which matched the original. This part is no longer made under this number so I received old stock. The replacement GM part no. is 7849305 (the one the dealer wants $500 for).
 

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(94+ do not). In 94 when they made an ECU, it did the speed controlling through I believe the alternator.
94+ use the Crankshaft position Sensor for engine speed to the PCM.
Alternator is for tachometer only.
 

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Hi, I have read most of your posts on the GMC transmission 4L80. I recently bought a diesel dully 6.5L with the 4L80. It would not shift out of 2nd so we changed out the VSS, that fixed it not shifting out of 2nd. Now it has hard shifts and will not go into overdrive. We will try to test it with what you have already suggested, but if you have anything else you can think of that would be great. Sounds like you really know this transmission. I really love this truck and would like to get it running. Thank you so much. Cindy
 

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I have a oil leak which I think is coming from the engine speed sensor that mounts where a distributor would be if it were gas. This is to the left of the OPS which I have already changed out cause of lift pump inop. What I would like it to confirm this is the speed sensor and where to get one and a part number. I have searched but no luck so far. I also have a SES light on when engine is cold. <<<NO CODES>>> Light goes out when engine is warm and as rpms go up. this effects my lockup convertor so as not to work when SES is on. does anyone know if this sensor could also cause this problem?


My truck is a 1992 GMC 6.5LTD 4L80E Auto 4x4


Thanks to all...


[EDITED BY ME, ADDED TEXT BELOW]


To help this I have found some info for all with same problem with SES light and trans shifting...
Constant or Intermittent MIL ON, No DTC's Set
Number: 93-33-6E
Section: 6E
Date: OCT. 1992
Corporate Bulletin No.: 177138R
ASE No.: A6
Subject:
CONSTANT OR INTERMITTENT ENGINE LIGHT
Model and Year:
1991-93 C/K, R/V, P AND G TRUCKS
TRANSMISSION APPLICATIONS:
1991-1993 HYDRA-MATIC
4L80-E/4L80-EHD (MT1)
TRANSMISSION MODELS:
All
SUBJECT:
Constant or Intermittent Check Engine Light, Line Pressure and TCC Fluctuation (No Codes Stored)
VEHICLE APPLICATIONS:
C, K, R, V, P Trucks, G-Van Equipped with LL4 6.2 Diesel or L65 6.5 Turbo Diesel
CONDITION:
Some 1991-1993 trucks equipped with the L65 6.5 Turbo Diesel or the LL4 6.2 Diesel and 4L80-E/4L80-EHD exhibit a constant or intermittent check engine light with the engine running and no codes stored.
CAUSE:
The 4L80-E/4L80-EHD use an engine speed sensor and if failure occurs a code will not be stored. Code 12 will be present with the engine running and the ALDL grounded. The electronic transmission control section of the 1991, 1992 and 1993 service manuals does not acknowledge the use of an engine speed sensor or code 12 for the L65 (6.5 turbo) or the LL4 (6.2) electronic transmission applications.
CORRECTION:
Check for proper engine speed sensor operation as follows:
1991 and 1992 Vehicles
For diagnosis, use the code 12 chart from the LH6 Diesel Emission Section of the 1991 or 1992 Service Manual (Pages 6E2-22 and 6E2-23). When following the trouble tree, substitute TCM PIN D7 for ECM PIN C1 and TCM PIN D6 for ECM PIN A8.
1993 Vehicles
For diagnosis, use the code 12 chart from the LH6 Diesel Emission Section of the 1993 Service Manual (Pages 6E2-22 and 6E2-23 for the G Van, Pages 6E2-32 and 6E2-33 for the C and K vehicles). When following the trouble tree, substitute TCM PIN D7 for PCM PIN F5 and TCM PIN D6 for PCM PIN F4.


Edited by: taz63nj2000
[/QUOTI
I HAVE A 92 CHEVY 2500 WITH 6.5 TURBO DIESEL THAT I AM TRYING TO FIND OUT WHAT VOLTAGE DOES THE ENGINE SPEED SENSOR HAVE WITH THE AC READING. I HAVE THE TRANSMISSION REBUILD AND NOW IT WOULD SHIFT OUT OF DRIVE. WHEN I START THE TRUCK THE SEL WILL BE OFF BUT WHEN I GO DOWN THE ROAD THE SEL WITH COME ON AND IT WILL NOT SHIFT INTO OD. I HAVE TRACED ALL THE WIRING DOWN NOTHING, THE GUY THAT REBUILT THE TRANSMISSION SAYS IT'S ELECTICAL..
 

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I HAVE A 92 CHEVY 2500 6.5 TURBO THAT WILL NOT SHIFT OUT OF FIRST. WHEN I START IT AND GO DOWN THE ROAD IT'S OK BUT WHEN I STOP AND TAKE OFF IT WILL STAY IN FIRST GEAR. AND THE SEL COMES ON. I HAD THE TRANSMISSION REBUILT AND THE TESTER PUT ON AND IT READS CODE 12 WHICH THE COMPUTER IS NOT TALKING TO THE TRANSMISSION. THE GUY THAT REBULT IT SAYS IT ELECTICAL BUT I HAVE TRACED ALL THE WIRES DOWN AND EVERYTHING IS FINE. WHAT OTHER THINGS CAN I TRY? I WAS WANTING TO SEE WHAT IS THE VOLTAGE READING FOR THE ENGINE SPEED SENSOR THAT HAS AC PORT. WHEN I PUT THE VOLTAGE METER ON IT'S READING 2.5-5. I HAVE LOOKED OTHER PLACES ONLINE BUT CANT FIND ANYTHING.
THANK CHRIS
 

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Welcome.
If you read the codes with the engine NOT running then you should get code 12.
Code 12 means there is no RPM signal.
If the engine IS running and you get code 12 then the ESS signal has a problem.
Is your engine original or has it been replaced?

7849305- ESS oil pump drive w/o vacuum pump - ACDELCO - 215-97
14022649 - Gasket for ESS or oil pump drive
 
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Welcome.
If you read the codes with the engine NOT running then you should get code 12.
Code 12 means there is no RPM signal.
If the engine IS running and you get code 12 then the ESS signal has a problem.
Is your engine original or has it been replaced?

7849305- ESS oil pump drive w/o vacuum pump - ACDELCO - 215-97
14022649 - Gasket for ESS or oil pump drive
The enigne is the orignal as far as we know. When this all started about 3 months ago it would throw a code 12, now we just put tester on will not throw a code but have first gear no other forward speeds with service engine light soon on, do have resevse, transmission has been rebuilt if light happens not to be on it shifts normal but will not last long. Tested AC voltage tested on ESS at idle was at .03 volt, increased RPM best we get as 2.5 volt at 2500 RPM. What would be your thoughts thank you.
 

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The enigne is the orignal as far as we know. When this all started about 3 months ago it would throw a code 12, now we just put tester on will not throw a code but have first gear no other forward speeds with service engine light soon on, do have resevse, transmission has been rebuilt if light happens not to be on it shifts normal but will not last long. Tested AC voltage tested on ESS at idle was at .03 volt, increased RPM best we get as 2.5 volt at 2500 RPM. What would be your thoughts thank you.
This is a new ESS.
 

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Have you checked all the grounds? Make sure the TCM is getting a good ground. Also check the electrical connection at the trans.
 

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Have checked connectors on transmission the one in transmission was replaced when rebuilt, the one outside the transmission that makes the connection was not replaced. but no moister or oil inside connector. Put electical contact grease on connections still no change. Should we change the outer connector???? Do you think the ess was okay with what we did just wanted to see what your thought were on that. Put extra ground on TCM, but no change on that either.
 

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Still have problems with the check engine light coming on. Was thinking about changing the connectors inside and outside of transmission. But wanting to get second option.
 
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