SENR6982_Systems Operation.pdf

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Systems OperationTRANSMISSION ELECTRONIC CONTROL FOR COUNTERSHAFT TRANSMISSIO FOR MOTOR

GRADERS

Systems Operation

Introduction

Transmission Electronic Control System(1) ECM. (2) Start switch. (3) Start relay. (4) Transmission control lever. (5) Transmission indicator lamp. (6) Manual modulationclutch switch. (7) Buffered transmission output speed. (8) Transmission speed sender. (9) Diagnostic connector. (10) Service tool.(11) Service tool connector. (12) Control valve. (13) Solenoid A. (14) Solenoid B. (15) Solenoid C. (16) Solenoid D. (17) SolenoidE. (18) Solenoid F. (19) Solenoid G. (20) Solenoid H. (21) Solenoid return. (22) Dual Horsepower Solenoid (VHP) solenoid. (23)Backup alarm. (24) Neutral output. (25) EMS output. (26) Action alarm. (27) EMS. (28) Action lamp.

Shutdown SIS

Previous Screen

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Media Number -SENR6982-02 Publication Date -24/01/1997 Date Updated -09/09/2002

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The transmission Electronic Control Module (ECM) shifts the machine transmission based on transmissionoutput speed (TOS), Transmission control lever position and transmission modulation (inching pedal)pressure switch position.

The transmission ECM processes information from the input components. Depending on the speed anddirection requested, the ECM then directs the signal to the specific combination of solenoids for that speedand direction.

If a fault occurs, the ECM directs a signal to the Electronic Monitoring System (EMS) group to alert theoperator of a problem. The technician has two methods of diagnosing problems with the transmissionelectrical system: the Electronic Control Analyzer Programmer (ECAP) via the service tool connector or thediagnostic connector and flash codes.

There is a unique transmission configuration code that must be programmed into the ECM with an ECAP,Electronic Technician (ET) or the transmission control lever. If a replacement is made to the ECM, the newECM must be programmed with this code. Without this code the machine will not operate. See "Using the8T-8697 Electronic Control Analyzer Programmer" section in the "Testing And Adjusting" portion of thismodule.

NOTE: The transmission solenoids are identified with letters (A through H) in this publication. Thesolenoids may also be identified with numbers (1 through 8). Solenoid 1 is Solenoid A, Solenoid 2 isSolenoid B, etc.

Definitions And Acronyms

CAT Data LinkA digital data communication link which is used to provide sharing of information between electroniccontrols and service tools on Caterpillar machines.

CID - Component IdentifierA three-digit number that is displayed to the technician on the ECAP service tool diagnostic display

during servicing. The number indicates the system component in question.Countershaft TransmissionThe transmission used on most "H" series motor graders and is shifted by means of electrohydraulicvalves which provide clutch control oil.

ECAP - Electronic Control Analyzer ProgrammerThe service tool used by the technician to gain access to the system status and diagnostic informationstored in the transmission ECM.

ECM - Electronic Control ModuleThe control is located under the operator's seat. It processes the input information which then directsthe proper electrical signals to the appropriate output devices for speeds, directions, and diagnostics.

EMS - Electronic Monitoring SystemThis is a dash-mounted device which alerts the operator to various machine status conditions.

ET - Electronic TechnicianThis is a personal computer version of the diagnostic software that is used in ECAP.FMI - Failure Mode Identifier

A two-digit "F" code that is displayed on the ECAP service tool diagnostic display during servicing.The number indicates the failure mode of the related component.

JumperA jumper is a piece of wire used to make an electrical connection during troubleshooting.

ScrollScrolling is the process of showing all available sets of diagnostic information, one set at a time. A setof diagnostic information is shown briefly and then the display automatically advances to the next set.




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TOS - Transmission Output SpeedA transmission signal generated by a magnetic pickup on the transmission output shaft.

VHP - Dual Horsepower Solenoid

Transmission Solenoid Locations

Solenoid Locations (Viewed From The Front Of The Machine)(1) Solenoid A. (2) Solenoid B. (3) Solenoid C. (4) Solenoid D. (5) Solenoid E. (6) Solenoid F. (7) Solenoid G. (8) Solenoid H.

NOTE: The transmission solenoids are identified with letters (A through H) in this publication. Thesolenoids may also be identified with numbers (1 through 8). Solenoid 1 is Solenoid A, Solenoid 2 isSolenoid B, etc.

(1) Transmission ECM. (Cover has been removed).




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CAT Data Link Operation

The CAT Data Link provides status information to other machine systems including All Wheel DriveControl and the ECAP service tool. The following parameters are available:

*Transmission Gear*Shift Lever Position*Transmission RPM (TOS)*Battery Voltage*Backup Alarm Status*Start Relay Status*Transmission Modulator Supply Pressure Status*Dual Horsepower Status*System Diagnostic Codes*Abusive Conditions*Coasting In Neutral*In Park With Machine Moving

Transmission ECM Connector Pin Assignments




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Transmission Gear Solenoids




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Transmission Diagnostic Code Conversion




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Electrical Inputs

Battery VoltageThis is a two wire input which provides 24 DCV nominal to drive the electronic circuits within the ECM andall of the external solenoids.

Start Switch Input

This is a single wire input that provides a battery voltage signal when the key start switch is in the Startposition.




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Transmission Shift Lever

This is a 13 wire input which provides the shift lever position to the ECM. Combinations of the 13 inputsbeing grounded correspond to the different shift lever positions.

Manual Modulation Supply Pressure Clutch Switch

This is a normally open switch and is located on the outermost valve body and monitors the supply pressureto the directional clutches and solenoids (Clutch 3 is Solenoid A, Clutch 1 is Solenoid B and Clutch 2 isSolenoid C). When the manual modulation pedal is depressed, the manual modulation valve inside thetransmission control valve disengages or reduces the power transmitted to the drive wheels by reducing thesupply or pilot pressure to the three directional modulating reducing valves. The pressure switch will close at75 kPa (11 psi) and open at 50 kPa (7 psi). It provides the ECM with the status of the manual modulationpressure.

Transmission Output Speed (TOS) Sensor Input

This is a single wire frequency input which receives a signal from a magnetic pickup speed sensor on thetransmission output.

Diagnostic Connector

This is a 3 wire input which provides a 3 bit code the ECM uses to determine which diagnostic mode to bein.

Electrical Outputs

Transmission SolenoidsThese solenoids are powered by 24 DCV from the ECM and are engaged when the ECM determines thecorrect time to be ON.

Start Relay

When the key start switch is turned to the Start position, 24 DCV is directed to the starter relay to engage thestarter motor if the transmission shift lever is not in a speed or direction.

Backup Alarm

When the transmission shift lever is moved to a Reverse speed, the ECM provides power for the backupalarm.

Dual Horsepower Solenoid (VHP)

When the transmission shift lever is moved to Fourth through Eighth Forward or Third though SixthReverse, the ECM provides power for the dual horsepower solenoid.




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NOTE: If the machine is a 143H or 163H All Wheel Drive, the ECM will provide power to the dualhorsepower solenoid any time the all wheel drive switch is moved to the Manual or Automatic position.

Diagnostic Output To EMS (Pin 8 On ECM)

The transmission ECM is connected to the EMS Panel Lamp Position 5 which is called the EMS ActionLight. If there is a problem in the transmission ECM system, the ECM disconnects the ground and the lampilluminates.

Neutral Output To EMS (Pin 7 On ECM)

The transmission ECM is connected to Pin 9 (Neutral) at the EMS control. Pin 9 has a function calledProgram Code 1 and is used to control the category of Alert Indicator 7 which is the Parking Brake indicator.Depending on the condition, the Parking Brake can be either a Category I or a Category III.

Service Tool Connector

This is a 2 wire digital data communication link that allows two way communication of the ECAP, ET orservice tool with the transmission ECM.

Transmission Indicator Lamp

This is used in conjunction with the diagnostic connector to visually flash light code sequences whendiagnosing transmission electrical system faults.

Buffered Transmission Output Speed (TOS)

This is the output from the transmission output speed sender after it goes through the ECM to the

speedometer.

Modes Of Operation

Power-up

Upon power-up, Solenoids D and G are energized and all other solenoids are de-energized. Normal operationis established once the shift lever has been moved to the Neutral or Park position.

Start

The transmission ECM has a neutral start feature. The operator controlled key switch is an input to the ECMwith the start relay being powered by an output from the ECM. This allows the ECM to inhibit starting themachine if certain conditions are not met. The shift lever must be in Neutral or Park before the ECM willallow the start relay to be energized.

Upshift

When the shift handle is moved from the current gear position to a higher gear position, the ECM will shift




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the transmission immediately. If an upshift is attempted with the transmission modulator pedal depressed, noaction by the ECM is taken until the transmission modulator pedal is released.

Downshift

When the shift handle is moved from the current gear position to a lower gear position, the ECM will shiftthe transmission immediately. If a downshift is attempted with the transmission modulator pedal depressed,no action is taken until the transmission modulator pedal is released. After it is released, the ECM willdetermine the proper gear.

If an overspeed condition occurs, the transmission is shifted to the lowest gear possible using special shiftpoints. Unit sequential downshifts result in the desired gear. If the TOS has not lowered below an overspeedcondition, the ECM will upshift to the appropriate gear.

Shift Out of Neutral

When the shift handle is moved from Neutral into a position which matches the direction the machine ismoving, the ECM will first check the TOS and determine if the requested gear can be obtained without

overspeeding the transmission. If no overspeed condition will occur, then the shift is made.

If a shift out of Neutral to the requested gear will cause an overspeed condition, the ECM will shift to thelowest gear possible.

When a shift out of Neutral is attempted with the transmission modulator pedal depressed, one of two thingswill happen:

*If the TOS is below First gear high idle, the shift is made immediately.*If the TOS is above First gear high idle, No Shift will be made until the TOS drops below First gearhigh idle or the transmission modulator pedal is released.

Shift Into Neutral

When the shift handle is moved from a gear position to Neutral, the ECM will shift the transmission toNeutral immediately. The status of the transmission modulator pedal or the TOS value does not matter.

Directional Shift

A directional shift is when the shift handle is moved from one gear position to another gear position of theopposite direction or where a shift out of Neutral is requested with the machine moving in the oppositedirection requested.

If the shift is requested with the TOS lower than Third gear high idle, the shift will be made immediately. Ifthe shift is requested with the TOS higher than Third gear high idle, the following steps will be taken:

1.The ECM will attempt to downshift the transmission to the lowest gear possible gear. If the TOS islowered below the Third gear high idle, the directional shift is made.

2.If the machine has not slowed to Third gear high idle, special shift points are used to downshift thetransmission until the TOS is below Third gear high idle.

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When a directional shift is requested with the transmission modulator pedal depressed, the following occurs:

1.If the TOS is at First gear low idle, the shift is made immediately.2.If the transmission modulator pedal is released when TOS is below Third gear high idle, the shiftwill be made immediately.

Overspeed

The ECM will automatically upshift above the shift lever position whenever the transmission reaches thepreset overspeed upshift rpm. There is No Limit to the number of upshifts allowed. If the ECM has alreadyautomatically upshifted because of an engine overspeed condition, the ECM will automatically downshiftwhenever the engine rpms are lowered and then match the shift lever position.

Diagnostic/Protection Mode

The transmission ECM will take special actions based on the present gear position and the type of faultdetected. The EMS transmission electrical fault indicator lamp will turn ON and remain on until the fault isremoved.

Service Mode

The Service Mode is enabled by uncoupling the diagnostic connector from the machine harness. This featureallows the technician to diagnose problems with the system using flash codes. This can be used when anECAP is not available.

Clutch Phasing

The transmission solenoids are disengaged and engaged with special timing to control the transmissionclutch pressures during shifts. Clutch phasing extends the life of the transmission clutches and makes for

smoother shifts.

Low Battery Voltage

When battery voltage drops below a certain level, the ECM will turn OFF all transmission solenoids exceptSolenoids D and G. If Solenoids D or G are already ON, they will be held on.

C Warning And Control Action Light

This warning system alerts the operator about operating the machine prior to the transmission oil being

warmed up. After machine startup, a temperature switch located at the transmission control valve determinesthat the oil is below 0C (32.0F) and a warning light in the center gage cluster alerts the operator to thiscondition.

The warning light is on if the oil is 0C (32.0F) or below, the light will also come on if there is an opencircuit. If the lamp in the gage panel is burned out, a level two alarm will come on.

Failure Modes




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Solenoid Faults

The detection of a system fault which prevents proper solenoid engagement for the selected gear will resultin the ECM causing the transmission to go to Neutral by using solenoids D and G (preferred), solenoid D,solenoid G, or all solenoids OFF (least preferred).

Keys For Charts 1 And 2

Chart 1

Open - Solenoid either Open or Shorted to Ground (solenoid OFF)




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NEU - Solenoid D & G Neutral

GNE - Solenoid G Neutral

DNE - Solenoid D Neutral

Chart 2

Sht+B - Solenoid Short to +Battery (solenoid ON)

NEU - Solenoid D & G Neutral

NCN - No Clutch Neutral

Shift Lever Switch Open Faults

The loss of a shift lever switch contact when leaving Neutral, First Forward, First Reverse, Second Forward,or Second Reverse will result in the machine remaining in Neutral. Loss of a shift lever switch contact when

in Third Forward or higher or Third Reverse or higher will result in remaining in the present gear. Whenevera shift lever switch contact is lost and either the Redundant Neutral or Neutral switches is lost, thetransmission will be neutralized.




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Shift Lever Switch Short Active Faults

Two active speed switches will result in the transmission remaining in the present gear until a valid speedsignal is detected or Neutral is requested. If the forward or reverse switches are active, then the transmissionwill be neutralized until a valid direction signal is determined.

Loss Of Or Erratic Transmission Output Speed (TOS) Signal

Loss of or erratic TOS will only result in the EMS Action Lamp and Action Alarm being turned ON to alertthe operator that further operation of the machine could cause damage. The overspeed feature will NOTfunction.

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SENR6982_Systems Operation.pdf

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