U0074 on 2013-2015 Chevrolet Malibu: Chassis Bus Communication Failure Causes and Fixes

What's Unique About the 2013-2015 Chevrolet MALIBU

The 2013-2015 Malibu, part of the 8th generation built on the GM Epsilon II platform, relies on multiple data networks. The U0074 code specifically points to a failure on the chassis bus, which is separate from the main high-speed bus for the engine and transmission. As noted in GM's Technical Service Bulletin #PIT5076E, this code, when seen with others, directs technicians to diagnose the chassis bus, highlighting the importance of this specific network for power steering and stability control functions. On this platform, the EBCM often acts as a gateway and can fail internally, causing the entire bus to shut down.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• "Service Power Steering" message on the dashboard
• "Service StabiliTrak" message on the dashboard
• ABS and Traction Control warning lights illuminated
🎬 Watch: A fast and easy fix for StabiliTrak and ABS lights.
• Loss of power steering assist, making the wheel hard to turn
• Instrument cluster gauges may drop to zero or behave erratically
• Transmission may not shift properly or get stuck in one gear.

Most Likely Causes

1. Failed Control Module (especially EBCM) 🔴 High Probability An internal failure within the Electronic Brake Control Module (EBCM) is a very common cause on this platform. It can fail in several ways: by shorting the network, ceasing communication, or through an intermittent internal failure of the 12-volt power supply it provides to other sensors on the bus. The Power Steering Control Module (PSCM) can also fail and cause the same code.
   How to confirm: This is typically a process of elimination. If the battery and wiring are good, a technician will use a scan tool to see which modules are offline. Tapping on the EBCM while monitoring sensor voltage with an oscilloscope can reveal an internal fault if the voltage drops out. Disconnecting modules one by one to see if communication is restored is a common diagnostic step.
   Typical fix: Replace the faulty control module. The new module will require programming to the vehicle's VIN.
   Est. part cost: $250-$800
2. Wiring Harness Damage or Corrosion 🟡 Medium Probability Wiring harnesses can rub against chassis components, bolts, or brackets over time, wearing through the insulation and causing a short circuit on the CAN bus wires. Connectors, especially those exposed to moisture, can also corrode, disrupting communication. On some GM platforms, chafing near the battery tray or transmission connectors are known weak points.
   How to confirm: Perform a thorough visual inspection of the wiring harnesses leading to the Electronic Brake Control Module (EBCM) and Power Steering Control Module (PSCM). Check for chafing, breaks, or corroded connector pins. A multimeter can be used to check for ~60 ohms of resistance between the CAN High and CAN Low pins at the DLC; a reading of 120 ohms or an open/short circuit indicates a wiring or module issue.
   Typical fix: Repair the damaged section of the wire and protect it from future chafing. Clean or replace corroded connectors and apply dielectric grease.
   Est. part cost: $10-$50
3. Weak or Failing 12V Battery ⚪ Low Probability Low system voltage can cause unpredictable electronic glitches, including communication network errors, as modules may not have enough power to operate correctly. While less common, it's the easiest and cheapest item to check first.
   How to confirm: Test the battery with a digital battery tester. A healthy battery should have at least 12.4 volts at rest and maintain voltage under load. 🎬 See how to properly test your battery for electronic glitches.
   Typical fix: Replace the vehicle's 12V battery.
   Est. part cost: $150-$250

Rare But Worth Checking

• Improperly Installed Aftermarket Accessories: If a remote starter, alarm, or stereo system was recently installed, it may have been incorrectly tapped into the CAN bus wiring, causing interference that triggers the U0074 code.
• Spread or Loose Connector Pins: Previous diagnostic attempts or vibrations can cause the female pins in a connector (often the EBCM connector) to spread, creating a poor connection. A 'drag test' with a male terminal is used to check for this. This issue was identified as the root cause on a platform-mate Buick after a previous shop's probing created the problem.

Diagnosis Steps

1. Check and verify the battery and charging system are operating correctly. Ensure battery voltage is above 12.4V.
2. Connect a professional scan tool to confirm which modules are not communicating on the network.
3. Prioritize diagnosis of the U0074 code before any other codes, as per GM guidance.
4. Perform a detailed visual inspection of the wiring harnesses and connectors for the Power Steering Control Module (PSCM) and Electronic Brake Control Module (EBCM). Look for any signs of chafing, damage, or corrosion.
5. Disconnect the battery. Measure the resistance between the CAN High and CAN Low pins at the Data Link Connector (DLC). A healthy bus should read approximately 60 ohms.
6. If the resistance is 120 ohms, it indicates an open circuit or a missing terminating resistor (often inside the EBCM or another module). If it's near 0 ohms, there is a short between the CAN wires.
7. If wiring checks out, the fault likely lies with a module. Isolate modules by disconnecting them one at a time to see if communication on the network is restored. The EBCM and PSCM are the primary suspects.
8. For intermittent issues, an oscilloscope may be needed to monitor the 12-volt supply from the EBCM to bus sensors. Tapping on the EBCM may reveal an internal fault if the voltage drops.
9. If a faulty module is identified, replace it and have it programmed by a qualified technician.

Parts You'll Likely Need

• Electronic Brake Control Module (EBCM) (OEM #23355954, 84074957, 84074960, 84256789 (superseded by 84256781)) — An internal failure in the EBCM can bring down the entire chassis communication bus, causing this code. This is a very common point of failure on the Epsilon II platform.
  Trusted brands: ACDelco (GM Original Equipment)
  OEM price range: $400-$700
  Aftermarket price range: $250-$500
• Power Steering Control Module (PSCM) — Like the EBCM, the PSCM is a key module on the chassis bus. If it fails, it can cause a total network shutdown. On the Malibu, this module is often integrated with the power steering rack or steering column assembly.
  Trusted brands: ACDelco
  OEM price range: $500-$900
  Aftermarket price range: $300-$600

Related Codes That Often Appear With This One

• U0125 — Lost Communication With Yaw Rate Sensor Module (part of the StabiliTrak system). This sensor is on the chassis bus.
• U0126 — Lost Communication With Steering Angle Sensor Module (part of the StabiliTrak/power steering system). This sensor is on the chassis bus.
• C0186, C0196, C0287 — These are chassis-related codes often seen alongside U0074, as mentioned in TSB #PIT5076E, pointing to a fault on the chassis bus.
• U0101 — Lost Communication With TCM. This can occur if the wiring fault is near the transmission or if a major network failure affects multiple buses.

Technical Service Bulletins (TSBs) & Recalls

• PIT5076E: Notes that if U0074 is set along with other specific codes, the technician should diagnose the Chassis bus. This TSB applies to the Malibu and its platform mates.

Platform-Specific Known Issues

• GM Technical Service Bulletin #PIT5076E directly lists U0074 as a code that points to a fault on the chassis bus, specifically involving the electronic brake or power steering control modules.
• Real-world diagnostics on a platform-mate (2010 Buick LaCrosse) with U0074 confirmed the root cause was an intermittent 12-volt power supply for bus sensors, which originated inside the EBCM. Tapping on the module would cause the failure.
• The Epsilon II platform, which this Malibu is built on, has a known pattern of EBCM failures leading to this code, affecting sister vehicles like the Buick Regal and Cadillac XTS.

Mechanic-Grade Diagnostic Values

• Chassis/High-Speed CAN Bus Resistance — expected: ~60 Ohms. Failure: A reading of ~120 Ohms indicates an open circuit or a module/terminating resistor is offline. A reading near 0 Ohms indicates the CAN High and Low wires are shorted together.
• CAN Bus High (CAN_H) Voltage — expected: 2.5 V to 3.5 V. Failure: Readings outside this range indicate a short to power, short to ground, or other wiring fault.
• CAN Bus Low (CAN_L) Voltage — expected: 1.5 V to 2.5 V. Failure: Readings outside this range indicate a short to power, short to ground, or other wiring fault.
• Module Ground Circuit Resistance — expected: Less than 5 Ohms. Failure: Resistance higher than 5 Ohms indicates a poor ground connection which can cause communication errors.

Hidden / Shadow Codes Worth Checking

• Symptom Code 71: A manufacturer-specific symptom code that may be stored in the Electronic Brake Control Module (EBCM) or Power Steering Control Module (PSCM) when a U0074 is present. (see via A professional GM-specific scan tool like the GDS2 (Global Diagnostic System 2) is typically required to view these sub-codes.)

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Module Programming — After replacing a control module like the EBCM, the new module must be programmed to the vehicle's VIN and configuration. Failure to program the module will result in it not functioning.
• GDS2 (GM Global Diagnostic System 2): Global Capacitive Discharge — On models with eAssist (2013-2014), if an extremely low voltage event (below 9V) occurs, modules can enter a 'logic lock' state. This function, performed after disconnecting the 12V battery, is required to reset them.

Wiring & Ground Locations

• DLC Pins 6 & 14 — Data Link Connector (OBD-II port) under the driver's side dashboard.. On the 2013-2015 Malibu, the EBCM and PSCM communicate on the High-Speed GMLAN bus. Resistance should be measured between Pin 6 (CAN High) and Pin 14 (CAN Low).
• G110 — Left front of the engine compartment.. This is a major engine bay ground point. A loose or corroded connection here can cause a variety of electrical faults, including module communication errors. A GM TSB also warns of improperly hardened ground bolts that fail to maintain clamp load.
• G203 — Located at the driver's side kick panel.. This is a key interior ground point for multiple modules. A poor connection here can disrupt communication networks.
• EBCM Connector — Located on the ABS pump assembly, near the brake master cylinder in the engine bay.. This is the primary connection point for the EBCM. It is susceptible to corrosion, and the female pins can become spread from vibration or improper probing, leading to intermittent communication loss.

Real Owner Repair Stories

• Pine Hollow Auto Diagnostics (YouTube) (2010 Buick LaCrosse (GM Epsilon II platform-mate)) — ABS CAN Bus Malfunction, code U0074.
  ❌ Tried (didn't work) A previous shop had already attempted repairs costing over $1000 without success.
  ✅ What actually fixed it The technician found that the female terminal pins for the CAN bus wires in the EBCM connector were spread open, causing a poor connection. This was likely caused by improper probing during a previous diagnostic attempt. The technician carefully re-tensioned the pins to restore a tight connection, which resolved the fault without replacing any parts.
• Reddit user on r/cruze (2014 Chevrolet Cruze (Related GM platform)) — "Service Power Steering" and "Service StabiliTrak" messages, U0101 code, limp mode, and scanner could no longer communicate.
  ❌ Tried (didn't work) Replacing the negative battery cable., Cleaning multiple ECM and battery cable harness connectors.
  ✅ What actually fixed it After multiple failed attempts, the owner discovered the bolts on the main underhood fuse box were loose. Tightening these bolts restored all functionality and cleared the codes. This indicates a poor main power or ground connection through the fuse box was causing the network failure.

OEM Part Supersession History

• 23355954, 84074957, 84074960, 84256789 → 84256781 — Standard part revision and consolidation by the manufacturer.
  Heads up: The new part number (84256781) is the correct service replacement for all the previous numbers and requires programming to the vehicle after installation.

Model Year Variations Within This Range

• 2013-2014: Models equipped with the 2.4L eAssist (mild hybrid) system have a Battery Energy Control Module and are sensitive to very low voltage events. A voltage drop below 9V can cause a 'logic lock' condition that disables the charging system and may set other communication codes, requiring a specific GDS2 reset procedure.
• 2015: The 2.5L base engine received start-stop technology, and the 2.4L eAssist option was discontinued for the 2015 model year.