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

Clarios Formalizes Joint Development Agreement with Altris

Altris will develop sodium ion cells for low-voltage tech while Clarios will lead in battery management systems, software, and system integration for battery design.

Clarios and Altris, a Swedish developer and prototype manufacturer of sodium-ion batteries, announced an exclusive Joint Development Agreement (JDA) for low-voltage mobility applications.

Under the new JDA, Altris will focus on developing the sodium ion cell technology for low-voltage applications, while Clarios will leverage its expertise in Battery Management Systems (BMS), software, and system integration to design the battery system. This development agreement enhances a collaboration agreement initiated earlier this year, which set in motion the creation of a detailed production plan for low-voltage vehicle batteries utilizing sodium-ion cells, the companies said.

Less is More with Cordless Work Lights

The automotive industry has reaped the benefits of LED lights more than any other industry.

Streamlight Wedge XT
Eaton to Supply ELocker Differential System to EV Manufacturer

The system leverages an electric motor to power the rear wheels and an electric motor or an optional ICE driving the front wheels.

Servicing EVs in Your Shop

Technicians need to learn how to correctly diagnose and repair electrical systems.

technician using laptop
Tool Time Podcast: Schrader TPMS

In this episode, Nadine and Eric sit down with Yanick Leduc to discuss all the TPMS solutions his company has to offer.

Other Posts

Eli Opens Reservations for its Micro-EV in the US

The new Eli ZERO represents a new category of high-tech, efficient and sustainable micro-EVs, according to Eli Electric Vehicles.

Hunter Engineering Releases New Alignment Coverage

Semi-annual specification update includes new and existing records.

#11 LED Work Lights

Light emitting diodes (LEDs) were a revolutionary development of electrical science.

LED Work Lights Feature
Eaton Receives 2024 Automotive News PACEpilot Award

Eaton was recognized for its 4-speed electrified vehicle transmission.