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Explorer 4WABS hydraulic control unit swap @ https://www.fullsizebronco.com/threads/explorer-4wabs-hydraulic-control-unit-swap.514736/
There have been a few threads on the site that discuss swapping an Explorer ABS hydraulic control unit into the Broncos with 4WABS. The recommendation was to use the HCU out of a 93-94. The only modification required is to modify the harness between the HCU and the control module. The connector is the same but it is reversed (male is female on the Explorer) and the isolate and dump valve pins are reversed on the harness. The previous write ups were helpful and I thought I could add to the knowledge base by adding some pictures and details on doing the swap.
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You can note some of the differences here. The Bronco HCU is on the left, the Explorer unit is on the right. The part numbers are F3TZ-2C215-B (Bronco) and the F3TZ-2C215-A (Explorer). I sourced the NOS Explorer unit on eBay from Spark Surplus out of Sugarland, Texas. I was happy with the price and it was well protected for shipping.
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The C121 connector between the HCU and control module from the Bronco is on the left (male pins), the Explorer on the right (female pins). If you want to remove the pins you will need to pull the red clip that holds them in place using a small needle nose pliers. You can also push the clip from the back side with a small nail when you back out the rubber wire seal. Pin number 1 is top right, pin 5 is bottom right for both connectors. You can transfer the Bronco connector by splicing the wires or you can source the correct male pins. I chose to splice the harness because I’m impatient and didn’t know where to get the pins.
I verified the resistance on all of the valves before I started cutting. I also labeled all of the Explorer leads prior to cutting.
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A4 MEASURE VALVE RESISTANCE AT ANTI-LOCK HYDRAULIC CONTROL UNIT
Disconnect the 8-pin connector from the anti-lock hydraulic control unit.
Measure resistance between the following on the COMPONENT side of the 8-pin connector:
Pin 1, Pin 4 and Pin 2 (rear axle outlet)
Pin 1, Pin 4 and Pin 3 (rear axle inlet)
Pin 1, Pin 4 and Pin 5 (front right inlet)
Pin 1, Pin 4 and Pin 6 (front left outlet)
Pin 1, Pin 4 and Pin 7 (front left inlet)
Pin 1, Pin 4 and Pin 8 (front right outlet)
NOTE: Refer to the system schematic for anti-lock hydraulic control unit pin designations.
All inlet valves should be 5-8 ohms.
All outlet valves should be 3-6 ohms.
Details on troubleshooting the Bronco HCU can be found in the following thread. My unit had infinite resistance on the rear dump pin 3.
ABS Code 17
I used the following thread to test the Explorer HCU and confirm how to map out the pins to the Bronco.
1993-1996 4WABS trouble codes WITH troubleshooting guide!
Long story short, you will need to reverse pins 2&3, 5&6, and 7&8 on the Explorer harness to match the Bronco wiring.
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Here is the harness after splicing which I protected with heat shrink tubing and plastic loom cover. It's a good idea to have the ABS wiring diagram handy when doing all of this. When you are done recheck that the resistance maps out properly. Then you are ready to install it in your Bronco.
After I installed the HCU I bled my brakes and started it up. No more ABS light! I did a quick test drive and the brakes felt great. I am going to find a dirt road tomorrow to do a few hard stops to cycle the HCU. Depending on how it goes I may also do the 'ghetto' bleed procedure linked below.
Ghetto 4WABS HCU Bleed Procedure
