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

I found part number and it is #7849305 http://www.dieselplace.com/forum/smileys/Big Smile.gif
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. http://www.dieselplace.com/forum/smileys/Approve.gif
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!!! http://www.dieselplace.com/forum/smileys/Angry.gif

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.

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.

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

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

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