Allison Transmission WTECII User Manual

Allison WTECII & WTECIII ECU’s (TCM’s) Power Failure
Troubleshooting Guide
Reference: https://www.transmissioninstruments.com/troubleshooting/
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Caution!!: The following procedures are technical and should not be attempted if you are unfamiliar with
electronics or uncomfortable working with electrical components. Doing this troubleshooting method is at
your own risk. Although this procedure has been recommended by other Monaco Owners, it should be
used with caution. If in doubt, contact Transmission Instruments (Click Here) for advice.
Have you recently replaced or charged the battery outside the vehicle? If yes, recheck connections in
your battery compartment and look for two 10 gauge wires. These are near the battery terminals which
supplies positive and negative power directly to your ECU through VIM (Vehicle Interface Module). The
VIM contains two fuses [for ECU only] and up to six relays powered by the ECU (including the start relay).
Recommended Tools :
Light Bulb Type Continuity Tester. Available at many autoparts stores.
Alternative: Assemble 12V/15-25W light bulb (spare brake lamp bulb or similar – #1156, #1073 etc.) with 20 gauge solid
copper wire (ordinary hookup or “bell wire”). Strip 1/2″ on test side.
When you check ECU connectors, the lamp must glow bright white light. A dim light will indicate a bad
connection somewhere; likely due to oxidization.
A voltmeter will not indicate bad connections. An ordinary voltmeter or VOM isn’t reliable for this test.
However you will need one to check the lower voltage systems.
 After assembly, check lamp directly on your battery terminals. Caution lamp will become
HOT!
 Always disconnect the battery or turn off the battery switch (Power Train Battery) prior to
disconnecting or reconnecting ECU connectors!

Allison Transmission WTECII Specifications

General

Brand	Allison Transmission
Model	WTECII
Category	Control Unit
Language	English

Summary

General Power Failure Troubleshooting

Safety Precautions for Troubleshooting

Technical procedures require caution; not for the unfamiliar.

Battery Connections and VIM Module Checks

Verify battery compartment connections and VIM fuses/relays.

Recommended Diagnostic Tools

Light bulb continuity tester or 12V/15-25W bulb with wire.

WTECII System Troubleshooting

WTECII Display and Code Issues

Address erratic displays or codes like 69-32 for 1992-1995 models.

ECU Location and Connector Checks

Locate ECU, disconnect battery, unplug connectors, and check wiring.

WTECII ECU Power and Ignition Testing

Test ECU power pins (#9, #12) and ground (#18, #11) using a test lamp.

Remote Shift Selector Testing

Test remote shift selector display using a 9V battery and hookup wire.

WTECIII System Troubleshooting

WTECIII Battery Terminal Swap Check

Check for ECU damage if battery terminals were accidentally swapped.

ECU Location and Connector Inspection

Locate ECU, disconnect battery, unplug connectors, and inspect.

WTECIII ECU Power and Ignition Tests

Test ECU power pins (#1, #16) and ground (#17, #32) with test lamp.

WTECIII Ignition and 5V Supply Checks

Check ignition power (#26/#4) and 5V supply on pin #3 with voltmeter.

WTECIII Shift Selector and Harness Testing

Test shift selector using 9V battery and check harness continuity.

WTECIII Connector Pinouts and Testing

Test shift selector pins P, R, N with voltmeter/9V battery and harness.

Troubleshooting Harness and ECU Issues

Diagnose harness damage or ECU failure based on voltage and continuity.