OK, double checked all of my connections,
and that WT/TN wire from #11 in the 40-pin BH connector is the only question that remains.
Actually, that entire 6-pin black plug that goes under the dash is the question.
Here's the diagram I've typed for this:
‘87 2.2 T2 LM/PM 40pin Bulkhead to ‘89 2.2 T2 50pin SMEC harness
Notes: (*) = wire not in 50-pin connector
(X2) = two wires in same pin
Note pin #32 in 40-pin connector; Simply delete one of the 2 DG/BK wires.
1987 40-pin connector_________________________________________ __________________________________________________ ____________1989 50-pin connector
(engine compartment side of connector)________________________________________ _________________________________(pin# reference for which wire in harness)
Pin #-Circuit-Color --- Description------------------------------------ Connect to ---- Pin# --- Circuit ------------------ Description-----------------
#1 - Not Used
#2 - Not Used
#3 - Not Used
#4 - J10-12PK---Ignition Switch ----------------------------------------- To ---------- (*) -12PK/BK--------------In Starter Harness Plug
#5 - L3-16RD(X2)-Left High Beam ----------------------------------------- To -----------#6 - L3-14RD/OR(X2)-----Headlamp High Beam
______________________Right High Beam
#6 - L1-12BK---Splice Charging Circuit Alternator ------------------------- To -----------#1 - L1-12RD-------------Battery Feed
#7 - B1 - 12WT---Back Up Lamp Switch ----------------------------------To -----------#27 - B1 -18WT----------Back Up Lamp Switch
#8 - B2 - 18VT/BK---Back Up Lamp Switch--------------------------------To------------#28 - B2- 18VT/BK------ Back Up Lamp Switch
__________________Neutral Start and Back Up lamp Switch
#9 - U3 - 20OR/LG---Fuel Pacer Lamp-------------------------------------To---- None: Delete wire from 40-pin
#10 - K3 - 20BK/OR---Power Loss Light Ground----------------------------To -----------#38 - K3 - 20BK/PK------ Check Engine Lamp
#11 - D4 - WT/TN---Brake Switch Signal---To---6-pin harness 18WT/PK(Remove WT/PK wire from 6-pin, solder to WT/TN wire; 6-pin other wiring is deleted)
#12 - C2 - 16DB/YL---A/C Low Pressure Switch----------------------------To-----------#37 - C20-18DB/OR--A/C Damped pressure Switch
#13 - D6 - 18LG---Left turn Signal----------------------------------------To-----------#21 - D6-18LG-------------Left Turn Signal Lamp
#14 - S2 - 18YL---Starter Relay-Ignition----------------------------------To-----------(*)- S2-14YL/BK---------In Starter Harness Plug
#15 - V3 - 18BR---Winshield Wiper Motor----------------------------------To-----------#45 - V3-18BR------------Windshield Wiper Motor
#16 - V4 - 18RD---Windshield Wiper Motor--------------------------------To-----------#46 - V4-18RD-------------Windshield Wiper Motor
#17 - G2 - 20VT--Water temperature Gauge or Lamp-----------------------To-----------#17 - G20-VT/YL-Water temperature Sending Unit
#18 - G6 - 20GY---Oil Pressure Switch------------------------------------To-----------#18 - G6-20GY-------------Oil pressure Switch
#19 - V5 - 18DG---Windshield Wiper Motor--------------------------------To-----------#35 - V5-18DG-----------Windshield Wiper Motor
#20 - V1 - 18DB----Windshield Wiper Motor-------------------------------To------------#36 - V6-18DB------------Windshield Wiper Motor
#21 - H2 - 18DG/RD---Horn----------------------------------------------To------------#32 - H2-14DG/RD-------Horn
#22 - Not Used
#23 - Not Used
#24 - L7 - 18BK/YL(X2)-Right Park & Side marker Lamps--------------------To-----------#26 - L7-18BK/YL(X2)---Splice Side Marker and Park and
_____________________Left Park & Side Marker Lamps___________________________________________Tu rn Signal lamps
#25 - A3 - 14PK-----Battery-Hazard Flasher-------------------------------To-----------#23 - A3-16PK/WT---Battery-Hazard Flasher
#26 - Not Used
#27 - G60 - 20GY/YL---Oil Pressure Sending Unit--------------------------To------------#19 - G60-20GY/YL---Oil Pressure Sending Unit
#28 - Not Used
#29 - P5 - 20BK---Brake Warning lamp Switch-----------------------------To------------#34 - P5-20GY/BK--Brake Warning Lamp Switch
#30 - Not Used
#31 - T21 - 20GY/LB----Tachometer--------------------------------------To-----------#33 - T21-20GY/LB--------Tachometer
#32(See notes) - Z1 - 14DG/BK(X2)--Fuel pump Feed--------------------To------------#24 - Z1-16DG/BK----------Fuel Pump Feed
#33 - V10 - 20BR---Windshield Washer Motor------------------------------To-----------#29 - V10-18BR----Windshield Washer Motor
#34 - D5 - 18TN-----Right Turn Signal-------------------------------------To-----------#22 - D5-18TN-------Right Turn Signal Lamp
#35 - C13 - 12BK/RD--Electrically Heated rear Window---------------------To-----------#48 - C13-12BK/RD-Electrically Heated Rear Window
#36 - Not Used
#37 - Not Used
#38 - J2 - 14DB(X2)----Splice Ignition Run Circuit--------------------------To----------#47 - J2-14DB(X2)------Splice Ignition Run Circuit
_____________________Splice ignition Run Circuit___________________________________________ ________Ignition Switch
#39 - L4 - 16VT(X2)----Right Headlamp Low Beam-------------------------To----------#35 - L4-14VT(X2)------Headlamp - Low Beam
_____________________Left Headlamp Low Beam
#40 - J1 - 12RD----Ignition Switch----------------------------------------To-----------(*) - J1-12RD------------In Starter Harness Plug
This sheet should be printable for anyone building a SMEC for their pre-1988 "L" body.
Best wishes with it.