Allison WTECII & WTECIII ECU’s (TCM’s) Power Failure
Troubleshooting Guide
Reference:
https://www.transmissioninstruments.com/troubleshooting/
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Connect negative terminal to #32 and positive terminal to #3 and #16. During power
“UP”, all segments display and RED LED (Mode)will be illuminated for 8 seconds and
then
display will show “cat eyes “.
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If one push button “D”,”N”, or “R” is held down during power “UP”, display will show
“D”, “N”, or “R” for 2 seconds only. This way you can check push button switches.
If display does not illuminate, the shift selector or harness may be defective.
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To check the harness, you must disconnect connect
or located 1/2′ from selector.
Then remove strain relief (black plastic) from vehicle harness connector and check
closely on the rear side for letters.
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“P” = GROUND “R” = POWER “N” = SENSOR POWER
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Insert 3 short lengths of hookup wire into sockets “P”, “R”, and “N”.
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Use a voltmeter to check voltage between “P” and “R” and between “P” and “N”; If
your using a 9V battery.
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If ECU and battery are still connected, insert lamp leads to “P” and “R”, then turn
ignition “ON” and with a voltmeter check for 5V in socket “N”.
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If you do have voltage and there is no display; shift selector is most likely defective. If
you do have voltage on ECU pins and not on the shifter connector; a defective
harness is indicated.
Check continuity with your ohmmeter between “P” and chassis ground.
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Should be less than 1 OHM.
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If the meter reads “open”, (Infinite resistance) find a good ground in the cabin, cut the
“P” wire 3″ from connector and reconnect with new ground.
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If missing 12V
– “R”, find “ignition” power, cut “R”, and reconnect with “ignition”
power.
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If missing “N” (5V ), cut “N” and reconnect with “ignition” power.
12V will not damage the shift selector. If one of three last steps will power up the shift
selector but has no response to commands. You may have additional harness damage or
defective ECU or shifter. In this case, you can send ECU + shifter for free testing (You only
pay for shipping) to
