SECTION 3 -- BASIC KNOWLEDGE

WTEC III ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

SECTION 3 -- BASIC KNOWLEDGE

31.

BASIC KNOWLEDGE REQUIRED

To service WTEC III Electronic Controls, the technician must understand basic electrical concepts. Technicians

need to know how to use a volt/ohmmeter (VOM) to make resistance and continuity checks. Most troubleshooting

checks consist of checking resistance, continuity, and checking for shorts between wires and to ground. The

technician should be able to use jumper wires and breakout harnesses and connectors. Technicians unsure of

making the required checks should ask questions of experienced personnel or find instruction.

The technician should also have the mechanical aptitude required to connect pressure gauges or transducers to

identified pressure ports used in the troubleshooting process. Pressure tap locations and pressure values are shown

in Appendix B -- Checking Clutch Pressures.

Input power, ground, neutral start circuitry, etc., can cause problems with electronic controls or vehicle functioning

and may not generate a diagnostic code. A working knowledge of WT Series Electronic Controls vehicle

installation is necessary in troubleshooting installation-related problems.

Refer to Section 8 for information concerning performance complaints (non-code) troubleshooting. A complete

wiring schematic is shown in Appendix J. Refer to the WTEC III Controls and General Information Sales Tech

Data Book for information concerning electronic controls installation and the Installation Checklist. Reliable

transmission operation and performance depend upon a correctly installed transmission. Review the Installation

Checklist in the MD, HD, B 300/B 400, and B 500 Sales Tech Data Books to ensure proper installation.

32.

USING THE TROUBLESHOOTING MANUAL

Use this manual as an aid to troubleshooting the WTEC III Electronic Controls. Every possible problem and its

solution cannot be encompassed by any manual. However, this manual does provide a starting point from which

most problems can be resolved.

Once a problem solution is discovered in the manual do not look further for other solutions. It is necessary to

determine why a problem occurred. For example, taping a wire that has been rubbing on a frame rail will not

correct the problem unless the rubbing contact is eliminated.

33.

SYSTEM OVERVIEW

WTEC III Electronic Control functions are controlled by the ECU. The ECU reads shift selector range selection,

output speed, and throttle position to determine when to command a shift. When a shift occurs, the ECU monitors

turbine speed, output speed, and throttle position to control the oncoming and off-going clutches during the shift.

When the ECU detects an electrical fault, it logs a diagnostic code indicating the faulty circuit and may alter the

transmission operation to prevent or reduce damage.

When the ECU detects a non-electrical problem while trying to make a shift, the ECU may try that shift a second or

third time before setting a diagnostic code. Once that shift has been retried, and a fault is still detected, the ECU

sets a diagnostic code and holds the transmission in a fail-to-range mode of operation.