Dodge Nitro. Manual - part 224

The HCU provides four channel pressure control to the front and rear brakes. Two channels control the rear 
wheel brakes individually. The two remaining channels control the front wheel brakes individually. 

During antilock braking, the solenoid valves are opened and closed as needed. The valves are not static. They 
are cycled rapidly and continuously to modulate pressure and control wheel slip and deceleration. 

During normal braking, the HCU solenoid valves and pump are not activated. The master cylinder and power 
booster operate the same as a vehicle without an ABS brake system. 

During antilock braking, solenoid valve pressure modulation occurs in three stages, pressure increase, pressure 
hold, and pressure decrease. The valves are all contained in the valve body portion of the HCU. 

PRESSURE DECREASE 

The outlet valve is opened and the inlet valve is closed during the pressure decrease cycle. 

A pressure decrease cycle is initiated when speed sensor signals indicate high wheel slip at one or more wheels. 
At this point, the ABM closes the inlet then opens the outlet valve, which also opens the return circuit to the 
accumulators. Fluid pressure is allowed to bleed off (decrease) as needed to prevent wheel lock. 

Once the period of high wheel slip has ended, the ABM closes the outlet valve and begins a pressure increase or 
hold cycle as needed. 

PRESSURE HOLD 

Both solenoid valves are closed in the pressure hold cycle. Fluid apply pressure in the control channel is 
maintained at a constant rate. The ABM maintains the hold cycle until sensor inputs indicate a pressure change 
is necessary. 

PRESSURE INCREASE 

The inlet valve is open and the outlet valve is closed during the pressure increase cycle. The pressure increase 
cycle is used to counteract unequal wheel speeds. This cycle controls re-application of fluid apply pressure due 
to changing road surfaces or wheel speed. 

REMOVAL 

HYDRAULIC CONTROL UNIT 

1. Install prop rod on the brake pedal to keep pressure on the brake system.  

2. Remove negative battery cable from the battery.  

3. Pull up on the ABM harness connector release and remove connector. 

 

2007 Dodge Nitro R/T 

2007 BRAKES ABS Service Information - Nitro

  

Fig. 11: Identifying Brake Lines & ABM 
Courtesy of CHRYSLER LLC 

4. Remove brake lines (1) from the ABM (2). 

Fig. 12: Identifying Bracket & ABM Unit 
Courtesy of CHRYSLER LLC 

5. Remove the ABM unit (2) by pulling the unit from the bracket (1).  

DISASSEMBLY 

HYDRAULIC CONTROL UNIT 

 

2007 Dodge Nitro R/T 

2007 BRAKES ABS Service Information - Nitro

  

Fig. 13: ABM & Mounting Screws 
Courtesy of CHRYSLER LLC 

1. Remove the four screws (1) attaching the ABM module to the HCU (2). See Fig. 13. 

1 - MOUNTING SCREWS
2 - ABM

 

2007 Dodge Nitro R/T 

2007 BRAKES ABS Service Information - Nitro

  

Fig. 14: Identifying ABM, HCU & Solenoid Valve Stem 
Courtesy of CHRYSLER LLC 

2. Separate the ABM module (1) from the HCU (2). See Fig. 14.  

ASSEMBLY 

HYDRAULIC CONTROL UNIT 

1 - ABM
2 - HCU
3 - SOLENOID VALVE STEM

 

2007 Dodge Nitro R/T 

2007 BRAKES ABS Service Information - Nitro