The through the firewall plug is for the later guages and HVAC system, IIRC. If you have the later parts, it all snaps together.
The later speedometer is all digital, and the tach in the later models uses a 4 cylinder input, the '89 speedo is mechanical, and the tach uses a 6 cylinder signal, so the ouput signal from the later PCM will cause the old style tach to read 2/3rd actual rpm.
If the two harnesses you are using are from different '91, '92 or '93 YJ's, the TSB/recall may have been done on one harness and not the other. If both harnesses are from the same Jeep, then this problem is unlikely to be the cause. A careful study of the harness colors as they go through the bulkhead will verify they are connected properly.
Here's the text of the #572 and #573 recall:
Subject: Safety Recall #572 / Customer Satisfaction Notification #573 Bulkhead Wiring Connector
Models:
Safety Recall #572 -- 1991 through 1993 Model Year Jeep Wrangler (YJ) Vehicles Equipped with a Manual Transmission Built Before February 23, 1993.
Customer Satisfaction Notification #573 -- 1991 through 1993 Model Year Jeep Wrangler (YJ) Vehicles Equipped with an Automatic Transmission Built Before February 23, 1993.
Salt tracking between the starter solenoid wire and the adjacent battery feed wire in the bulkhead connector may bypass the key control of the starter motor solenoid circuit and cause the starter to engage without ignition key initiation. This may cause vehicles equipped with a manual transmission and parked in gear to move without warning due to engine cranking. To correct the condition, the starter solenoid wiring must be relocated within the bulkhead connector.
Service Procedure
With the ignition key in the OFF position, disconnect the negative battery cable.
Disconnect the engine compartment bulkhead connector.
Separate the larger section of the bulkhead wiring connector from the connector.
Remove the blue wedge.
FOR 1991 - 1992 MY VEHICLES: Remove the green wire from cavity G5 and install it in cavity A6 (Figure 1).
FOR 1993 MY VEHICLES WITHOUT ABS: Remove the yellow wire from cavity G5 and install it in cavity A6 (Figure 1).
FOR 1993 MY VEHICLES WITH ABS: Remove the yellow wire from cavity G5 and install it in cavity A6. Remove the existing white/tan wire from cavity A6 and install it in cavity G5 (Figure 1).
Reinstall the blue wedge.
Reunite the two sections of the bulkhead connector.
Remove the two fuse block/instrument panel bulkhead connector attaching screws.
Separate the fuse block from the bulkhead connector.
Separate the larger section of the bulkhead wiring connector from the connector.
Remove the blue wedge.
FOR 1991 - 1992 MY VEHICLES: Remove the green wire from cavity G5 and install it in cavity A6 (Figure 2).
FOR 1993 MY VEHICLES: Remove the yellow wire from cavity G5 and install it in cavity A6. Remove the existing white/tan wire from cavity A6 and install it in cavity G5 (Figure 2).
Reinstall the blue wedge.
Reunite the two sections of the bulkhead connector.
Reattach the fuse block to the bulkhead connector.
Install the fuse block/instrument panel bulkhead connector with the two attaching screws.
Reconnect the engine compartment bulkhead connector.
Connect the battery negative cable.
If you can get the engine to turn over by jumping the relay connections in the PDC relay center, then there is the possibility that the relay is not grounded. If you are using a transmission harness that was originally from an automatic, there is a neutral safety wire to the Neutral safety/reverse switch that needs to have a ground for the starter relay to work. This wire is the one in the middle of the switch connector, the two outer wires are for the reverse lights. If your harness is from a YJ with a manual transmission, one of the small ground wires to the stud that holds the dipstick to the block is the ground for the starter relay, IIRC.
You can verify that the relay in the PDC is getting ground to one of the side terminals, (#85, or #86) and the other side is getting the start signal from the key switch when it's in the start position.
Hope this helps!
