Frame and Underbody Cadillac Escalade GMT900

Fastener Tightening Specifications

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DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit/System Description

The assist step control module (ASC) controls the running board actuators to extend or retract the running boards. Each actuator consists of an electric motor and a potentiometer. The module supplies a low reference and 10-volt reference source voltage to the potentiometer. The ASC control module monitors the voltage drop across the potentiometer on the position signal circuit. When the actuator shaft rotates, the voltage on the position signal circuit changes. The ASC control module supplies the actuator motor with a 12-volt control circuit and a ground control circuit. The ASC module controls the direction of the actuator by changing the polarity of the control circuits.

Conditions for Running the DTC

1. The ignition is ON.
2. Ignition voltage is between 9-16 volts.
3. The ASC disable switch is not pressed.

B051A 0B, B051B 0B

The motor control circuits are shorted together.

B051A 01, B051B 01

A motor control circuit is shorted to battery voltage.

B051A 02, B051B 02

A motor control circuit is shorted to ground.

B051A 04, B051B 04

A motor control circuit is open.

B051C 01

The hall sensor 10 V reference is shorted to battery voltage.

B051C 02

The hall sensor 10 V reference is shorted to ground.

B051C 2A, B051D 2A

The hall sensor counts are greater than what is required to extend or stow the running board.

B051C 22, B051D 22

The hall sensor signal is noisy.

B051C 29, B051D 29

No hall sensor counts are detected while the motor is active.

B051C 62, B051D 62

The running board stow time is greater than 4 seconds.

B051C 63, B051D 63

The running board extend time is greater than 4 seconds.

Action Taken When the DTC Sets

Driver A and driver B circuits are deactivated for the appropriate actuator.

Conditions for Clearing the DTC

1. The DTC becomes history when the ASC control module no longer detects the condition that set the DTC.
2. The history DTC will clear after 50 fault free ignition cycles.

Reference Information

Schematic Reference

Step/Running Board Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Running Board Description

Electrical Information Reference

1. «Circuit Testing»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

OPEN and CLOSE each vehicle door, the running boards should extend when the door is OPENED, and retract when the door is CLOSED.

Circuit/System Testing

Note. If DTC B051C and/or B051D with symptom bytes 62, 63, or 2A is set, verify that the assist step motor wedge is present and the assist step motor wedge bolt is tight prior to proceeding with the following diagnostic steps. Refer to Assist Step Motor Replacement (Power BRS) for part location and tightening specifications.

1. Ignition OFF, disconnect the harness connector at the appropriate actuator.
2. Scan tool disconnected, test for less than 20 ohms between the low reference circuit terminal C and ground. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ASC control module.
3. Ignition ON, command the appropriate actuator with a scan tool while using the DMM Min/Max function to capture voltage. Test for greater than 9 volts between the 10-volt reference circuit terminal D and ground. If less than the specified range, test the 10-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ASC control module.
4. Command the appropriate actuator with a scan tool while using the DMM Min/Max function to capture voltage. Test for greater than 9 volts between the signal circuit terminal E and ground. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ASC control module.
5. Connect a test lamp between the control circuit terminal A and the control circuit terminal B.
6. Command the ASE Board to Extend and Retract with a scan tool. The test lamp should turn ON when commanding the Extend and Retract states. If the test lamp remains OFF during either of the commands, test for a short to ground or an open/high resistance on either control circuit. If the circuits test normal, replace the ASC control module.
7. If all circuits test normal, replace the ASC motor.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Assist Step Motor Replacement (Power BRS)»(/cadillac/escalade/gmt900-2006-2014/remont/frames-subframes-crossmembers/#frame-and-underbody)
2. «Control Module References»(/cadillac/escalade/gmt900-2006-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for ASC control module replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The assist step control module (ASC) controls the assist step actuators to extend or retract the assist steps. Each actuator consists of an electric motor and a potentiometer. The module supplies a low reference and 10-volt reference source voltage to the potentiometer. The ASC module monitors the voltage drop across the potentiometer on the position signal circuit. When the actuator shaft rotates, the voltage on the position signal circuit changes. The ASC module supplies the actuator motor with a 12-volt control circuit and a ground control circuit. The ASC module controls the direction of the actuator by changing the polarity of the control circuits.

Schematic Reference

Step/Running Board Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Running Board Description

Electrical Information Reference

1. «Circuit Testing»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

1. Observe the scan tool ASC Disable Switch parameter while activating and deactivating the power assist steps. The reading should change between Active and Inactive. If the parameter does not change between the specified values, refer to ASC Disable Switch Circuit Test in «Circuit/System Testing»(/cadillac/escalade/gmt900-2006-2014/remont/frames-subframes-crossmembers/#frame-and-underbody) .
2. Power assist steps enabled, OPEN and CLOSE each vehicle door, the assist steps should extend when the door is OPENED, and retract when the door is CLOSED. If the function does not perform as specified, refer to ASC Actuator Circuit Test in «Circuit/System Testing»(/cadillac/escalade/gmt900-2006-2014/remont/frames-subframes-crossmembers/#frame-and-underbody) .

ASC Disable Switch Circuit Test

1. Ignition OFF, disconnect the harness connector at the IP multifunction switch.
2. Test for less than 10 ohms between the listed ground circuit terminal and ground. X88/Z88 Terminal 3 Z75 terminal 1 If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool ASC Disable Switch parameter is Inactive. If not the specified value, test the signal circuit terminal 9 for a short to ground. If the circuit tests normal, replace the ASC module.
4. Install a 3A fused jumper wire between the signal circuit terminal 9 and ground. Verify the scan tool ASC Disable Switch parameter is Active. If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ASC module.
5. If all circuits test normal, test or replace the IP multifunction switch.

ASC Actuator Circuit Test

1. Ignition OFF, disconnect the harness connector at the appropriate actuator.
2. Scan tool disconnected, test for less than 20 ohms between the low reference circuit terminal C and ground. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ASC module.
3. Ignition ON, command the appropriate actuator with a scan tool while using the DMM Min/Max function to capture voltage. Test for greater than 9 volts between the 10-volt reference circuit terminal D and ground. If less than the specified range, test the 10-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ASC module.
4. Command the appropriate actuator with a scan tool while using the DMM Min/Max function to capture voltage. Test for greater than 9 volts between the signal circuit terminal E and ground. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ASC module.
5. Using a scan tool, command the appropriate actuator both directions while using the DMM Min/Max function to capture voltage. Test for greater than 2 volts between the control circuit terminal A and ground. If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ASC module.
6. Using a scan tool, command the appropriate actuator both directions while using the DMM Min/Max function to capture voltage. Test for greater than 2 volts between the control circuit terminal B and ground. If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ASC module.
7. If all circuits test normal, replace the ASC actuator.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Assist Step Motor Replacement (Power BRS)»(/cadillac/escalade/gmt900-2006-2014/remont/frames-subframes-crossmembers/#frame-and-underbody)
2. «Control Module References»(/cadillac/escalade/gmt900-2006-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for ASC module replacement, setup, and programming

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Removal Procedure

1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#general-information__lifting-and-jacking-the-vehicle) .
2. Remove the mounting bolts for the oil pan skid plate.
3. Remove the oil pan skid plate.
4. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#general-information__lifting-and-jacking-the-vehicle) .
5. Remove the mounting bolts for the oil pan skid plate.
6. Remove the oil pan skid plate.

Installation Procedure

1. Position the oil skid plate on the frame.
2. Install the oil skid plate mounting bolts and tighten to 28 N.m (21 lb ft).

1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#general-information__lifting-and-jacking-the-vehicle) .
2. Remove the mounting bolts for the oil pan skid plate.
3. Remove the oil pan skid plate.

1. Position the oil pan skid plate on the frame.
2. Install the oil skid plate mounting bolts and tighten to 28 N.m (21 lb ft).
3. Lower the vehicle.

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1. Remove the master cylinder. Perform the following steps: Remove the nuts retaining the master cylinder to the brake booster. Remove the master cylinder from the brake booster. Secure the cylinder away from the booster.
2. Raise the vehicle on the hoist. Refer to «Lifting and Jacking the Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#general-information__lifting-and-jacking-the-vehicle) .
3. Remove the park brake equalizer intermediate cable. Perform the following steps: Remove the nut from the park brake equalizer intermediate cable. Remove the intermediate cable from the equalizer. Depress the retaining tabs that secure the park brake cable to the frame. Pull slightly on the cable from the mounting area in order to provide slack for body movement without binding the cable.
4. Remove the body mount bolts.
5. Properly support the body in the area that the mounts will be replaced.
6. Lower the chassis accordingly in order to remove the cushions (1) as necessary.

1. Install the cushions (1) as necessary and raise the chassis accordingly.
2. Perform the following procedure before installing the bolts. Remove all traces of the original adhesive patch. Clean the threads of the bolt with denatured alcohol or equivalent and allow to dry. Apply threadlocker GM P/N 12345493 (Canadian P/N 10953488).
3. Install the body mount bolts and tighten to 60 N.m (44 lb ft) plus 200 degrees.
4. Install the park brake equalizer intermediate cable. Perform the following steps: Pull rearward on the park brake cable to the original position. Secure the cable retaining tabs to the frame. Install the intermediate cable end to the equalizer. Install the nut to the threaded end of the intermediate cable and tighten to 4 N.m (31 lb in).
5. Lower the vehicle.
6. Install the master cylinder. Perform the following steps: Mount the master cylinder to the brake booster. Install the master cylinder mounting nuts and tighten to 36 N.m (27 lb ft).

1. Remove the master cylinder. Perform the following steps: Remove the nuts retaining the master cylinder to the brake booster. Remove the master cylinder from the brake booster. Secure the cylinder away from the booster.
2. Raise the vehicle on the hoist. Refer to «Lifting and Jacking the Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#general-information__lifting-and-jacking-the-vehicle) .
3. Remove the park brake equalizer intermediate cable. Perform the following steps: Remove the nut from the park brake equalizer intermediate cable. Remove the intermediate cable from the equalizer. Depress the retaining tabs that secure the park brake cable to the frame. Pull slightly on the cable from the mounting area in order to provide slack for body movement without binding the cable.
4. Remove the body mount bolts.
5. Properly support the body in the area that the mounts will be replaced.
6. Lower the chassis accordingly in order to remove the cushions (1), as necessary.

1. Install the cushions (1) as necessary and raise the chassis accordingly.
2. Perform the following procedure before installing the bolts. Remove all traces of the original adhesive patch. Clean the threads of the bolt with denatured alcohol or equivalent and allow to dry. Apply threadlocker GM P/N 12345493 (Canadian P/N 10953488).
3. Install the body mount bolts and tighten to 60 N.m (44 lb ft) plus 200 degrees.
4. Install the park brake equalizer intermediate cable. Perform the following steps: Pull rearward on the park brake cable to the original position. Secure the cable retaining tabs to the frame. Install the intermediate cable end to the equalizer. Install the nut to the threaded end of the intermediate cable and tighten to 4 N.m (31 lb in).
5. Lower the vehicle.
6. Install the master cylinder. Perform the following steps: Mount the master cylinder to the brake booster. Install the master cylinder mounting nuts and tighten to 36 N.m (27 lb ft).

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Front Wheelhouse Liner Replacement - Left Side

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1. Disconnect the trailer wiring harness.
2. Remove the hitch platform bolts from the frame rails and the rear bumper.
3. Remove the hitch platform from the vehicle.

1. Position the hitch platform to the vehicle.
2. Install the platform hitch bolts to the frame rails and the rear bumper. Tighten the trailer hitch-to-frame bolts to 113 N.m (83 lb ft). Tighten the trailer hitch-to-bumper bolts to 100 N.m (74 lb ft).
3. Connect the trailer wiring harness.

Assist Step Controller System Components

The assist step controller system consists of the following components

1. Assist step controller disable switch
2. Passenger side assist step motor
3. Driver side assist step motor
4. Passenger side power assist step
5. Driver side power assist step
6. Assist step controller (ASC)

Operation

A power extend operation will occur with the opening of either the front or rear doors on the assist step on that side of the vehicle. A power retract operation will occur with the closing of both doors on the assist step on that side of the vehicle. A door open/close status switch input is received by the assist step controller through the GMLAN serial data line. The park brake switch and vehicle speed inputs are is also received by the assist step controller through the GMLAN serial data line. The assist steps will be disabled when the disable switch is pushed once. The assist steps will be enabled with a second push of the disable switch.

Each assist step has a bi-directional motor and a hall-effect sensor to detect the position of the assist step. The hall-effect sensors are included with the motor assembly. The polarity on each motor is switched to reverse the direction of assist step travel.

Object Detection

Each assist step will reverse direction of travel when an object is detected in the travel path. If an assist step is moving in the retract direction, the assist step will move to the full extend position if an object is detected. If a door on the same side as the extended assist step is opened and then closed, the assist step will move to the retract position. The assist steps will stop and hold if after two failed retracting attempts an object is detected when retracting and the vehicle is in the drive position with vehicle speed above 5 mph.

Learn Procedure

When the assist step controller is replaced, or loses battery power, the assist step controller must learn the position of both assist steps. At least one door must be opened and closed on each side of the vehicle for both assist steps to go to a learn procedure. Each assist step will extend and then retract after a door is opened and closed on that assist steps side of the vehicle. Each assist step will learn its own position with the learn procedure

Assist Step Controller Disable Switch

The disable switch input is normally pulled to B+ through a resistor in the assist step controller. The disable switch sends a ground signal to the assist step controller with a switch closure. The assist steps will move to a retract position once all doors are closed and remain retracted until the disable switch is opened and a door on the same side as the retracted assist step is opened. An assist step that is extended when the disable switch is active will retract when the vehicle speed reaches 5 mph or the vehicle is shifted from the park position to the drive position.

Shipping Mode Unlock Procedure

The vehicles with the power running boards are shipped from the assembly plant in a shipping mode. The boards are locked in a retracted position during shipping. To unlock the boards for normal operation, perform the following steps

1. Open both drivers side doors
2. Set the park brake
3. Toggle the disable switch three times within 20 seconds after turning the ignition switch to the "On" position

See also:
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Component Connector End Views
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Control Module References
• Diagnostic Repair Verification
• Fastener Caution
• Lifting and Jacking the Vehicle
• Tire and Wheel Removal and Installation
• DTC B051A, B051B, B051C, or B051D