ABS/TCS - Brake/ABS/TCS Lamps ON/Multiple DTC's Set
TECHNICALBulletin No.: 08-05-25-006A
Date: March 25, 2009
Subject:
Hybrid Two-Mode Red Brake Telltale Illuminates Under High Braking Demand or Heavy Regenerative Braking, ABS Traction Control And/Or StabiliTrak Lights On With DTCs C056D 00, C12F3, C12F4 and C12F6 (Check Brake Pedal Travel and Bleed Brake System)
Models:
2009 Cadillac Escalade Hybrid
2008-2009 Chevrolet Silverado Hybrid, Tahoe Hybrid
2008-2009 GMC Sierra Hybrid, Yukon Hybrid
with Two-Mode Hybrid System (RPO HP2)
with Active Apply, Disc/Disc, With VSES, With Regen, 7,700 lb Brake System (RPO J92)
Supercede:
This bulletin is being revised to add the 2009 Chevrolet Silverado and GMC Sierra Hybrid Truck Models. Please discard Corporate Bulletin Number 08-05-25-006 (Section 05 - Brakes).
Condition
Some customers may comment that a red brake telltale illuminates in stop and go traffic under high braking demand or heavy regenerative braking and the ABS lamp is illuminated followed by a" Service Stability Message" displayed in the Driver Information Center.
During diagnosis, the technician may find any or all of the following Electronic Brake Control Module (EBCM) and Electrical Control Module (ECM) diagnostic codes set:
- C056D 00 : ECU Hardware Performance
- C12F3 : ECU Hardware Performance (ABS Left Isolation Solenoid Valve Performance)
- C12F4 : ECU Hardware Performance (ABS Right Rear Isolation Solenoid Valve Performance)
- C12F6 : ECU Hardware Performance (ABS Proportioning Valve Solenoid Performance)
Cause
This condition may be caused by an incomplete brake bleeding procedure, allowing the control module to learn invalid actuator offsets.
Correction
Warning
The high pressure accumulator (HPA) and the chambers of the brake modulator assembly to which it attaches, store brake fluid at extremely high pressures. Fluid pressure must be relieved before attempting to bleed the brake system. Ensure that the recommended procedures are followed to relieve system pressure, to avoid brake fluid spray. Failure to properly follow procedures to depressurize the system may result in personal injury or damage to the vehicle. Refer to Brake Fluid Irritant Warning and Brake Fluid Effects on Paint and Electrical Components Caution in SI.
Note
Install a midtronics battery charger or equivalent on the vehicle to maintain the battery voltage.
Note
The brake corners must be cool to obtain the most accurate measurement.
Check the brake pedal travel and perform the automated brake bleed procedure with the Tech 2(R) following the procedure below.
1. Place the transmission in the PARK position.
Note
The ignition must be in the OFF position, without pausing at ACCESSORY, and without applying the brake pedal to ensure the brake modulator and high pressure accumulator (HPA) pressure relief occurs. This process will take approximately 1-3 minutes.
2. Turn the ignition key to the "OFF" position, without pausing at ACCESSORY, and without applying the brake pedal. Remove the ignition key.
3. Wait approximately 1 to 3 minutes until the brake modulator and HPA pressure relief is complete.
4. Without the brake pedal applied, turn the ignition key to the "ON" position, with the engine OFF.
5. Using the Tech 2(R) scan tool, check the brake pedal travel using the steps below:
1. Select Diagnostics.
2. Build the appropriate vehicle information.
3. Select Chassis.
4. Select if the vehicle is equipped with Magnetic Ride Control Suspension Package (RPO Z95).
5. Select Electronic Brake Control Module (EBCM).
6. Select Data Display.
7. Under the Data List, scroll down the list and select "BMC Primary Piston Ref. Position" and "Master Cylinder Pressure Sensor" items as shown:
Note
First highlight the line and press the "Enter" soft key on the Tech 2(R) to get the "*" as shown for each item.
- BMC Primary Piston Ref. Position
- Master Cylinder Pressure Sensor
- Then "Accept" the two selected items as shown on the top of the Tech 2(R) scan tool.
6. While observing the Master Cylinder Pressure Sensor on the scan tool data display, using moderate speed and moderate effort, depress the brake pedal to a force of 5,000 kPa (725 psi).
7. Record the distance displayed on the scan tool that the BMC Primary Piston has travelled at the applied brake pedal force of 5,000 kPa (725 psi).
8. Release the brake pedal.
9. Wait 15 seconds, then repeat steps 6-8 to obtain a second measurement.
10. Compute the average of the first and second measurements recorded during the brake applies.
Specification
Maximum brake master cylinder (BMC) primary piston travel, (measured with the ignition ON, engine OFF, brake modulator and HPA depressurized, and the brakes cool), at a brake pedal apply force of 5,000 kPa (725 psi) : 18 mm (0.71 in).
Warning
It is recommended that you use the J-29532-A pressure bleeder or a diaphragm type (ball bleeder) which is capable of delivering 200 kPa (30 psi) for the bleed procedure. Follow and read all the directions on the Tech 2(R) for completing the Automated Bleed procedure and do every step during the bleed procedure. If you miss a step, you must start over. The EBCM Relearn will occur during the automated brake bleed procedure, so make sure you maintain battery voltage during the entire procedure. Failure to provide a constant 200 kPa (30 psi) may cause air to be trapped in the brake system and may cause brake performance problems or DTCs to occur. Tool J-29532-A has been tested extensively on this application and has proven to provide the necessary pressure and volume of brake fluid. Vacuum bleeding and other brake bleeding tools are NOT acceptable for this procedure.
- If the brake pedal travel is greater than 18 mm (0.71 in), perform the following steps:
1. Inspect the brake system for leaks and visual damage. Repair or replace the components as necessary.
2. Perform the automated brake bleed procedure. Refer to Antilock Brake System Automated Bleed Procedure-Hybrid (HP2) in SI.
- If the brake pedal feels spongy and/or the brake pedal travel is still excessive after performing the automated brake bleed procedure and no external brake fluid leaks or damage were found, inspect the hydraulic brake system for internal leaks, etc. Refer to Hydraulic Brake System Diagnosis (Two-mode Hybrid) in SI.
11. Clear all the codes from the modules.
12. Start the vehicle and allow the brake system to pressurize.
13. Drive the vehicle up to 32 km/h (20 mph) and perform several heavy brake stops.
14. Verify that the condition has been corrected.
Warranty Information
For vehicles repaired under warranty, use the table.
Disclaimer