Vibration/Shudder when applying brakes at highway speeds

Jesse, The module will not stop fluid to rear brakes, a bad master cylinder will,leaking lines, air in brake system, faulty metering block if equipped, collapsed flex lines or pinched brake line faulty caliper or brake cylinders,etc. will cause the possible feeling of no rear brakes.
(ABS Module components) the ABS speed sensors and the ABS control module . When the brake is applied, the ABS control module reads the speed data from the speed sensor and sends the correct pressure to each wheel to prevent any wheel lock up, eg. sliding/skidding Links below have more info.
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Service Stability System AND abs Pump issue

ABS Control Module Replacement Service Cost YourMechanic

https://www.rockauto.com/en/catalog/cadillac,2002,escalade,5.3l+v8,1431695,brake/wheel+hub,abs+control+module,1844

The light being on means the system has detected a problem in one or more sensors. The vibration is the ABS modulating the brakes to prevent skidding because it has detected a wheel that is locked up. That wheel is most likely the one sensor that is giving you the error.

Having the vehicle checked for DTC'S - diagnostic trouble code's would be a good first step . ABS light on codes are stored . Suggest you take your vehicle to a qualified repair shop that has the knowledge an testing equipment to diagnose the problem properly .
Anti-Lock Brake System (ABS)
The 4-wheel, 4-channel anti-lock brake system (ABS) consists of the following components:

• ABS module
• Front wheel speed sensor
• Front wheel speed sensor ring (integral to the front wheel bearing)
• Hydraulic control unit (HCU)
• Rear wheel speed sensor
• Rear wheel speed sensor ring (integral to the rear halfshaft)
• Yellow ABS warning indicator
• As you can see here , it can set numerous
• DTC'S Why guess an replace parts that won't fix the problem .
• Anti-Lock Brake System (ABS) Module Diagnostic Trouble Code (DTC) Index DTC Description Source Action B1342 ECU is Faulted ABS Module NOTE: If other DTCs are present, REPAIR them before installing a new component.
  CLEAR the DTCs. RETRIEVE the DTCs. If DTC B1342 is retrieved, INSTALL a new module. REFER to Anti-Lock Brake System (ABS) Module in this section. REPEAT the self-test. B1483 Brake Pedal Input Circuit Failure ABS Module Go To Pinpoint Test B . B1676 Battery Pack Voltage Out of Range ABS Module Go To Pinpoint Test C . B2477 Module Configuration Failure ABS Module CONFIGURE the ABS module. REFER to Section 418-01 . CLEAR the DTCs. REPEAT the self-test. If DTC B2477 is retrieved again, INSTALL a new ABS module. REFER to Anti-Lock Brake System (ABS) Module . REPEAT the self-test. B2734 Pedal Travel Sensor Supply Error ABS Module Go To Pinpoint Test M . B2736 Pedal Travel Sensor Circuit Fault ABS Module Go To Pinpoint Test M . B2737 Pedal Travel Sensor Jammed Error ABS Module Go To Pinpoint Test M . B2738 Pedal Travel Sensor Velocity Error ABS Module Go To Pinpoint Test M . B2740 Pedal Travel Sensor Spike Error ABS Module Go To Pinpoint Test M . B2741 Sensor Cluster Defective ABS Module FOLLOW the diagnostic tool directions for the calibration procedure. B2900 VIN Mismatch ABS Module VERIFY that the module has the correct as-built data.
  CHECK for correct powertrain control module (PCM) and ABS module configurations using the diagnostic tool. RECONFIGURE the component as necessary. FOLLOW the diagnostic tool directions for the ABS module configuration or REFER to Section 418-01 for the PCM. CLEAR the DTC. REPEAT the self-test. C1095 ABS Hydraulic Pump Motor Circuit Failure ABS Module Go To Pinpoint Test D . C1145 Speed Wheel Sensor RF Input Circuit Failure ABS Module Go To Pinpoint Test E . C1155 Speed Wheel Sensor LF Input Circuit Failure ABS Module Go To Pinpoint Test E . C1165 Speed Wheel Sensor RR Input Circuit Failure ABS Module Go To Pinpoint Test E . C1175 Speed Wheel Sensor LR Input Circuit Failure ABS Module Go To Pinpoint Test E . C1233 Speed Wheel LF Input Signal Missing ABS Module Go To Pinpoint Test F . C1234 Speed Wheel RF Input Signal Missing ABS Module Go To Pinpoint Test F . C1235 Speed Wheel RR Input Signal Missing ABS Module Go To Pinpoint Test F . C1236 Speed Wheel LR Input Signal Missing ABS Module Go To Pinpoint Test F . C1277 Steering Wheel Angle 1 and 2 Circuit Failure ABS Module Go To Pinpoint Test G . C1278 Steering Wheel Angle 1 and 2 Signal Faulted ABS Module Go To Pinpoint Test G . C1279 Yaw Rate Sensor Circuit Failure (Sensor Cluster Fault) ABS Module Go To Pinpoint Test H . C1280 Yaw Rate Sensor Signal Fault (Sensor Cluster Fault) ABS Module Go To Pinpoint Test H . C1281 Lateral Accelerometer Circuit Failure (Sensor Cluster Fault) ABS Module Go To Pinpoint Test H . C1282 Lateral Accelerometer Signal Fault (Sensor Cluster Fault) ABS Module Go To Pinpoint Test H . C1285 Booster Solenoid Circuit Failure ABS Module Go To Pinpoint Test I . C1287 Booster Pedal Force Switch Circuit Failure ABS Module Go To Pinpoint Test J . C1288 Pressure Sensor Main/Primary Input Circuit Failure ABS Module Go To Pinpoint Test K . C1440 (with stability assist) Pressure Sensor Main/Primary Signal Faulted ABS Module Go To Pinpoint Test K . C1516 Roll Rate Sensor Signal Fault (Sensor Cluster Fault) ABS Module Go To Pinpoint Test H . C1517 Roll Rate Sensor Circuit Failure (Sensor Cluster Fault) ABS Module Go To Pinpoint Test H . C1730 Reference Voltage Out of Range (+5V) ABS Module Go To Pinpoint Test L . C1805 Mismatched PCM and/or ABS-TC Module ABS Module CHECK for correct PCM and ABS module configuration using the diagnostic tool. RECONFIGURE the component as necessary. FOLLOW the diagnostic tool directions for the ABS module configuration or REFER to Section 303-01 for the PCM. CLEAR the DTC. REPEAT the self-test. C1963 Stability Control Inhibit Warning ABS Module This DTC is for information only. GO to the Principles of Operation. CLEAR the DTC. REPEAT the self-test. C1991 Module Calibration Failure ABS Module Follow the diagnostic tool directions for the calibration procedure. C1996 Active Yaw and/or Roll Control Disabled ABS Module This DTC can be set if the ABS module system is activated for 15 seconds of continuous operation. CHECK for any major chassis modifications, gross suspension misalignment or other items that can alter the vehicle tracking dynamics. CLEAR the DTC. REPEAT the self-test. C1998 Module Calibration Not Complete ABS Module Go To Pinpoint Test O . C2769 (ABS only) Longitudinal Acceleration Sensor Electrical Failure ABS Module INSTALL a new ABS module. REFER to Anti-Lock Brake System (ABS) Module in this section. CLEAR the DTCs. REPEAT the self-test. C2769 (ABS with stability assist) Longitudinal Acceleration Sensor Electrical Failure (Sensor Cluster Fault) ABS Module Go To Pinpoint Test H . C2770 (ABS only) Longitudinal Acceleration Sensor Plausibility Failure ABS Module INSTALL a new ABS module. REFER to Anti-Lock Brake System (ABS) Module in this section. CLEAR the DTCs. REPEAT the self-test. C2770 (ABS with stability assist) Longitudinal Acceleration Sensor Plausibility Failure (Sensor Cluster Fault) ABS Module Go To Pinpoint Test H . C2777 Sensor Cluster Bus Failure (Sensor Cluster Fault) ABS Module Go To Pinpoint Test H . C2778 Sensor Cluster Power Supply Failure (Sensor Cluster Fault) ABS Module Go To Pinpoint Test H . U1900 CAN Communication Bus Fault-Receive Error Network Fault REFER to Section 418-00 . U1901 CAN Network #2 Communication Bus Fault-Receive Error Network Fault Go To Pinpoint Test H . U2023 Fault Received from External Node Instrument Cluster REFER to Section 418-00 .

ABS------ Anti Lock Brakes will cause a chatter if applied with a lot of weight pushing it. An E350 is a big rig.
Might ask your Ford Tech about that possibility.

Hi:
The ABS light on means an ABS malfunction. You should be able to have a auto parts store scan your car and find out what code is tripped, for free, but my guess is that one of your front wheel speed sensors is out of whack, or dirty or something.
When the light is on, your normal brakes work fine, but you have no ABS, so your car will take longer to stop in emergency situations.

YOU NEED A SCANNER TO MONITOR THE WHEEL SPEED SENSORS. THE ABS IS SENSING A SKID AND THE ABS IS ACTIVATED WHEN THIS HAPPENS. THERE MAY BE A CODE FOR THE HUB THAT IS CAUSING THE ABS TO ACTIVATE.

CHECK THE WIRES FROM THE SENSORS FOR BREAKS OR CHAFFING. AN OHM READING OF THE SENSOR SHOULD BE 850-1200 OHMS, AND AND A-C VOLTAGE READING SHOULD BE 100 MV WITH YOU TURNING THE WHEEL BY HAND.

RATE ME, PLEASE

this may actually be the ABS pump.

I would pull the fuse for the ABS hydraulic pump and then put it back in and see what happens. Don't ever recall a pump running. Dealer may need to hook up scan tool for diagnostic fault codes, DTCs.



Principles of Operation
The ABS control module receives wheel speed readings from both front wheel speed sensors and the rear differential speed sensor, and processes this information to determine if an ABS event is necessary. The wheel speed sensor electrically senses each tooth of the ABS sensor indicators as it passes through the wheel speed sensor's magnetic field.
The ABS control module continuously monitors and compares the rotational speed of each wheel speed sensor indicator and, when it detects an impending wheel lock, modulates brake pressure to the appropriate brake caliper(s). This is accomplished by triggering the hydraulic control unit (HCU) to open and close the appropriate solenoid valves. Once the affected wheel returns to normal speed, the ABS control module returns the solenoid valves to their normal position, and normal (base) braking resumes.
The ABS control module is self-monitoring. When the ignition switch is turned to the RUN position, the ABS control module will do a preliminary electrical check, and at approximately 20 km/h (12 mph), the pump motor is turned on for approximately one-half second. Any malfunction of the ABS system will cause the ABS to shut off; normal power assisted braking, however, remains.
Inspection and Verification — Scan Tool Communications Check

1. Verify the customer concern by carrying out the Drive Cycle Test.

1. Visually inspect for obvious signs of mechanical and electrical damage.

Visual Inspection Chart Mechanical Electrical

• Parking brake cable
• Tire pressure
• Tire size or mismatched tires

• Blown fuse
• Central junction box (CJB):
  • fuse 23 (10A)
• Battery junction box
  • fuse 102 (50A)
• Connectors or connections
• Ground integrity
• Harness routing
• Wire chafing
• Circuitry open/shorted

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Anti-Lock Control The four-wheel anti-lock brake system (4WABS) consists of the following components:

• Anti-lock brake control module (2C265)
• Front anti-lock brake sensor (2C204)
• Front anti-lock brake sensor indicator (2C182)
• Hydraulic control unit (2C219)
• Rear anti-lock brake sensor (2C190)
• Rear anti-lock brake sensor indicator (2C189)
• Yellow ABS warning indicator

first your shudder is a warped brake rotor and you always grind or replace them in pairs.
and your sensor
90% of the time its a broken wire just check before you replave you sensor

Its possible that right wheel speed sensor is dropping out early making the truck think that wheel is locking up. That will activate the ABS and let the brake go on the right wheel which will make the vehicle pull slightly left. The only way to know for sure is to watch the wheel speeds on a scanner and see which one is drpping out first and replacing that speed sensor/bearing assembly.

good Luck