Instructions for WTECIII system (single red digit on Your shift selector)

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!

Have you recently replaced the battery and accidentally swapped the battery terminals? If “YES”, the ECU may be fried beyond repair. If “NOT”, locate the ECU (in most RV’s it is near shift selector, close to the VIM Module or mostly on trucks, close to transmission (just follow bundle of wires from transmission). Disconnect the battery first, then unplug all three connectors from ECU and reconnect battery. Closely check the GRAY connector for numbers. Insert test lamp leads into corresponding connector sockets: 1 and 32 then 16 and 17.

Next turn “ON” Ignition switch and insert test leads to 17 and 26. If cavity #26 is blank, use BLACK connector socket #4. Lamp must glow brightly.

#17; #32 = BATTERY GROUND; #1; #16 = BATTERY POWER; #26 gray or #4 black = IGNITION

Next turn ignition and battery “OFF”, reconnect GRAY ECU connector only, then reconnect battery and turn “ON” ignition. Then very carefully touch gold plated pins #16 and #32 (on ECU BLACK connector) with lamp test leads. Lamp must glow bright. Then use a voltmeter to check 5V on pin #3 (on ECU BLACK connector) against chassis ground. DO NOT use test lamp! If no 5V is found on pin #3, ECU is defective.

Also check socket #3 on BLACK connector with ohmmeter against chassis ground. Must be over 4k ohms.

Shift selector can be checked using ordinary 9V battery and hookup wire. Connect the 9V battery using hookup wire which you may have to slightly bent on the ends so they can hold inside BLACK connector sockets. 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 “. 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. To check the harness, you must disconnect connector located 1/2′ from selector. Then remove strain relief (black plastic) from vehicle harness connector and check closely on the rear side for letters.

Insert 3 short lengths of hookup wire into sockets “P”, “R”, and “N”. Use a voltmeter to check voltage between “P” and “R” and between “P” and “N”; If your using a 9V battery. 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”. 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. Should be less than 1 OHM. 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. If missing 12V – “R”, find “ignition” power, cut “R”, and reconnect with “ignition” power. 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 testing the cost is $55 plus shipping.