Chevy Silverado Tech Tip: ABS Light Comes on at 40-50 mph

Chevy Silverado Tech Tip: ABS Light Comes on at 40-50 mph

At speeds over 40-50 mph, the ABS and brake indicators come on, and the fuel and volt gauges sometimes drop low at the same time. The technician had already verified the condition and checked for codes before calling Identifix. He found code C0237 (rear wheel speed signal erratic) stored as a history code, but it had not reappeared for him.

Vehicle: 1999 Silverado.

Customer Complaint: At speeds over 40-50 mph, the ABS and brake indicators come on, and the fuel and volt gauges sometimes drop low at the same time.

The technician had already verified the condition and checked for codes before calling Identifix. He found code C0237 (rear wheel speed signal erratic) stored as a history code, but it had not reappeared for him. Next he road-tested with a scanner, watching the vehicle speed input through the powertrain control module (PCM) and electronic brake control module (EBCM) data. When the ABS and brake light came back on, data was lost on the scanner for both the PCM and ABS. Something was crashing the class 2 data line — but what?

On this truck, the instrument panel cluster (IPC), body control module (BCM), EBCM, PCM and automatic transfer case control module (ATC) are all on the class 2 data line at pin 2 of the data link connector. The tech went to the splice pack (SP205) to determine which module was initially causing the problem. The splice pack joins all of the data circuits at one point, and is located on the lower left side of the dash behind the headlamp switch. The splice pack, a connector end with a jumper bar seated into it, is located on a short harness and often is taped to another harness. When the EBCM class 2 data wires were disconnected from the data line, the symptom was gone. Now we knew the EBCM circuit was causing the problem, so that left either a problem with the power/ground or the EBCM.

The tech checked the connector at the EBCM for corrosion and terminal condition — it was OK. Next he removed and cleaned the ground for the EBCM at the frame (see GM bulletin #04-05-25-002A). Using a headlamp to load the circuit, he load-tested the power and ground to the EBCM. The power and ground tested OK, but there was still a problem. A new EBCM fixed this one.

Written by IDENTIFIX GM Specialist Bill Siegmann. Bill is certified ASE Master and L1 with 20 years of diagnostic and repair experience.

For additional tech tips, visit www.identifix.com.

You May Also Like

Decrypting Brake Pad Edge Codes

Learning the cryptic codes on the brake pad or shoe will tell you a lot of information.

Just about every brake pad or shoe you install has a cryptic code printed on the side of the friction material or on the backing plate. As a technician, being able to read this code called the “Edge Code” is just as important as the Dewy Decimal system is to a librarian.

Auto Pros on the Road: Curt’s Service

Detroit-area full-service facility completed an “all-green” expansion for comfort and safety of techs and clients.

Bartec USA To Host TIA’s ATS Class at Their Facility

Classes will be held from April 25-28.

J.D. Power Study: EV Market Growth Fuels Owner Satisfaction

Overall satisfaction with the BEV purchase experience is shifting to more traditional factors, like quality and styling.

Gen 1 Wheel Bearings

Removing and installing these bearings requires the correct tools and patience.

Other Posts

Lexus and Toyota Camera Calibration (VIDEO)

Joe Keene discusses how to calibrate the camera on a 2021 Lexus UX where the camera was removed and reinstalled.

TechShop Reveal: Streamlight Stinger Color-Rite Flashlight

TechShop Reveal provides a 360 product video highlighting the industry’s latest innovations.

Utilizing NVH Tools

Technology has been improving on NVH tools over the years.

AAPEX 2022: Get to Know Performance Ride Technology

PRT displayed a new product line and its extensive portfolio of heavy-duty applications at AAPEX 2022.