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

Were things better when they were simpler? Probably not.  

Last month, Andrew Markel purchased a 1982 Chrysler New Yorker for $1,500.

1982 Chrysler New Yorker

Last month, I purchased a 1982 Chrysler New Yorker for $1,500. The car was previously owned by a technician who was moving to Arizona. It had 67,000 original miles. It would be my “beater with a heater” for this winter.

Under the hood is a 318 V8 with a Lean Burn feedback carburetor with a rudimentary engine control module attached to the air cleaner. The system could adjust the spark advance, change metering in the carburetor and even open a solenoid to vent the evaporative emissions from the fuel tank.

Branford Public Schools Award $60M Transportation Contract to Zum

Within five years, Zum will transition Branford to a 100% electric school bus fleet, the first in Connecticut.

Tesla Model 3 TPMS Service

Resetting and programming TPMS sensors for a Tesla is a lot like any other vehicle, and the challenge is still the same: keeping the light off.

Can You Jumpstart an EV?

First thing’s first: Find the LV battery, which could be anywhere in the vehicle.

ADAS Module Programming

Reflashing and reprogramming is a necessary service for repairing vehicles.

Other Posts

Mullen Road Tests Solid-State Polymer Battery Pack

The results met or exceeded all requirements targeted for the first drive cycles for energy usage and driving range.

Understanding What Antifreeze/Coolant Actually Does

Today, each manufacturer has its own formula for best results in their vehicles. This video is part of the Group Training Academy.

How The Vehicle Cooling System Functions

Here’s what to know to clarify cooling questions you’re asked at the service counter. This video is part of The Group Training Academy.

Oil Filter Housing Weak Points & Standard® Solutions

Engineers at Standard® have created a completely assembled Oil Filter Housing Kit.