U0074 on 2015-2018 GMC Yukon: Control Module Communication Bus 'B' Off Fixes

What's Unique About the 2015-2018 Gmc YUKON

On this generation of GMC Yukon and its sister platforms (Tahoe, Suburban, Escalade), the U0074 code is frequently linked to a loss of communication between the Engine Control Module (ECM) and the Fuel Pump Control Module (FPCM). GM has issued technical service bulletins (TSBs) that instruct technicians to prioritize diagnosing this communication code before addressing any resulting fuel pressure codes, as the network failure is the root cause. In some cases, this communication breakdown can even lead to the replacement of the ECM itself.

Diagnostic Flowchart

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

Symptoms You May Notice

• Check Engine Light (Malfunction Indicator Lamp) is on.
• Service StabiliTrak warning message.
• Service Power Steering warning message.
• ABS light is on.
• Fuel gauge may read empty even with fuel in the tank.
• Engine may run rough, stall, or not start.
• Actual fuel pressure may read significantly higher than desired fuel pressure on a scan tool.
• Loss of power windows, door locks, or interior lights in some cases.

Most Likely Causes

1. Faulty Fuel Pump Control Module (FPCM) 🔴 High Probability The FPCM is a well-documented failure point on this platform. Its location on the frame rail exposes it to moisture and vibration. TSBs point to communication loss with this specific module as a primary cause for U0074 when seen with fuel pressure codes. Recalls for faulty FPCMs have been issued for similar GM vehicles.
   How to confirm: A technician will use a scan tool to see if the FPCM is offline. They will then check for power, ground, and communication signals at the FPCM connector, which is located on the driver's side frame rail, often near the rear of the driver's side passenger door. Wiggling the harness at the FPCM connector while monitoring voltage can reveal loose or spread terminals.
   Typical fix: Replacement of the Fuel Pump Control Module. The new module may require programming, although some aftermarket units are sold as 'pre-programmed'.
   Est. part cost: $80-$200
2. Wiring Harness Damage or Corrosion 🟡 Medium Probability Wiring harnesses, especially those routed along the frame or under the driver's seat, are susceptible to damage from moisture, road salt, and vibration, leading to shorts or open circuits in the CAN bus wires. The harness and connector for the FPCM are particularly vulnerable. A break has been noted to occur in the harness where it makes a turn under the truck frame, directly under the driver's side fuse panel.
   How to confirm: Visually inspect known problem areas of the harness for chafing, breaks, or corroded connectors. A multimeter is used to check for continuity and shorts to ground on the CAN bus circuits. Pay close attention to the large X411 connector if applicable to your vehicle's specific bus topology, as it's a known failure point on other GM platforms for U0074.
   Typical fix: Repairing the damaged section of the wiring harness and protecting it from future damage. This may involve soldering wires, replacing connector terminals, and using heat-shrink tubing and dielectric grease.
   Est. part cost: $10-$50
3. Poor Ground Connection ⚪ Low Probability Ground points on the frame or engine block can corrode over time, creating high resistance that disrupts module communication. Forum users have identified the frame grounds located behind both front wheels as being in a 'terrible location' prone to corrosion from tire splash.
   How to confirm: Locate the main ground points for the affected modules (e.g., ECM, BCM, FPCM) and inspect them for corrosion or looseness. Key locations include the firewall ground strap, frame grounds behind front wheels, and an interior BCM ground near the A-pillar. Perform a voltage drop test on the ground circuit.
   Typical fix: Remove the ground connection, clean the contact surfaces on the terminal and the frame/engine block until they are bare metal, and re-secure the connection tightly. Apply dielectric grease or a protective coating to prevent future corrosion.
   Est. part cost: $1-$10
4. Faulty Engine Control Module (ECM) ⚪ Low Probability In some documented cases, after all wiring and other modules have been checked, the internal circuitry of the ECM that controls communication with the FPCM fails.
   How to confirm: This is typically a diagnosis of last resort. If the FPCM is good, and the wiring between the ECM and FPCM has perfect continuity and is not shorted, the ECM is the likely culprit. This requires ruling out all other possibilities first.
   Typical fix: Replacement of the Engine Control Module, which requires programming to the vehicle's VIN.
   Est. part cost: $400-$800

Rare But Worth Checking

• Faulty Electronic Brake Control Module (EBCM): TSB #PIT5076E mentions that U0074 can be set in relation to the EBCM. The EBCM often contains a terminating resistor for the CAN bus, and a failure within the module can take down the entire network. This is a more common cause on other GM platforms like the Cadillac SRX.
• Improperly Installed Aftermarket Accessories: Aftermarket alarms, remote starters, or audio systems that are improperly spliced into the vehicle's wiring can interfere with or damage the CAN bus network, causing communication codes like U0074.

Diagnosis Steps

1. Scan for all DTCs in all modules. Note all communication codes (U-codes) and any other codes present.
2. Prioritize diagnosis of U0074 before any other codes, as per GM TSB PIP5427B.
3. Check battery voltage and main ground connections. Ensure voltage is stable and above 12.4 volts. Inspect grounds on the firewall and frame behind the front wheels.
4. Using a scan tool, attempt to communicate with all modules on the network (ECM, EBCM, FPCM, PSCM, etc.). Identify which modules are not responding.
5. Locate the Fuel Pump Control Module (FPCM) on the driver's side frame rail. Visually inspect the module and its connector for corrosion or damage.
6. Inspect the wiring harness and connectors between the non-communicating modules, paying close attention to the harness along the frame rail and under the driver's side of the vehicle.
7. Check for power and ground at the connector of the non-communicating module (often the FPCM). Wiggle the connector and harness to check for intermittent connections.
8. If wiring, power, and ground are good, test the CAN bus. Disconnect the battery and measure the resistance between the two CAN wires (pins 6 and 14) at the OBD-II port. It should be approximately 60 ohms. A reading of 120 ohms indicates a break in the circuit or a missing terminating resistor.
9. If resistance is incorrect, begin unplugging modules on the affected bus (FPCM, EBCM) one by one to isolate the faulty module or wiring section.
10. If all wiring and other modules check out, suspect a faulty primary control module like the ECM.

Parts You'll Likely Need

• Fuel Pump Power Control Module (FPCM) (OEM #13554821) — This is a very common failure point on 2015-2018 GM trucks and SUVs that directly causes code U0074. This part number supersedes older versions including 13544950, 13544060, 13537053, 13534714, and 13545846.
  Trusted brands: ACDelco (Genuine GM), Dorman
  OEM price range: $120-$200
  Aftermarket price range: $80-$150
• Engine Control Module (ECM) — In cases where the FPCM and wiring are confirmed to be good, the ECM itself can be the source of the communication failure.
  Trusted brands: ACDelco
  OEM price range: $500-$800
  Aftermarket price range: $300-$500

Related Codes That Often Appear With This One

• P2635 — This code for 'Fuel Pump Flow Performance' is often triggered as a direct result of the U0074 communication failure between the ECM and the FPCM.
• U18A2 — This is another communication code. TSB #PIP5427B states that if both U0074 and U18A2 are present, the diagnostics for U0074 should be performed first.
• P018B — This code relates to the fuel pressure sensor. It can be set when the FPCM defaults to maximum pressure due to the loss of communication, causing the actual pressure to be much higher than what the ECM desires.

Technical Service Bulletins (TSBs) & Recalls

• PIP5427B: Advises technicians to diagnose communication DTCs like U0074 before addressing fuel pressure DTCs like P2635, as the communication loss is the root cause. Confirms this applies to Yukon, Tahoe, Suburban, Escalade, Silverado, and Sierra.
• PIT5076E: Suggests diagnosing the 'Chassis bus' if U0074 is present with other specific chassis-related codes, pointing towards the EBCM or PSCM networks.

Platform-Specific Known Issues

• A known issue, documented in TSB #PIP5427B, involves a loss of communication between the Engine Control Module and the Fuel Pump Control Module, which can cause U0074 along with fuel pressure codes like P2635. The bulletin explicitly states to diagnose the U-code first.
• TSB #PIT5076E points to faults on the 'Chassis bus' when U0074 is present, indicating potential issues with wiring or modules related to the brake (EBCM) or power steering (PSCM) systems.

Mechanic-Grade Diagnostic Values

• CAN Bus Resistance (High-Speed GMLAN) — expected: ~60 Ohms between Pin 6 (CAN High) and Pin 14 (CAN Low) at the OBD-II port with the battery disconnected.. Failure: A reading of ~120 Ohms indicates an open circuit or a missing terminating resistor (often in the EBCM or ECM). A reading near 0 Ohms indicates a short between the CAN High and Low wires.
• CAN Bus Voltage (Key On, Engine Off) — expected: CAN High (Pin 6) should be ~2.5V to ground, pulsing toward 3.5V. CAN Low (Pin 14) should be ~2.5V to ground, pulsing toward 1.5V.. Failure: Voltages stuck high, low, or at 0V indicate a short to power or ground on the bus.
• FPCM Serial Data Enable Voltage — expected: Approximately 12V (battery voltage) on the Dark Green/White wire (Pin 13) at the FPCM connector with the key in the RUN position.. Failure: Low or no voltage indicates a wiring issue between the ECM and FPCM, or a fault in the ECM itself. The ECM sends this signal to 'wake up' the FPCM.
• Low-Side Fuel Pressure (Scan Tool Data) — expected: Desired and actual fuel pressure should be relatively close at idle (e.g., ~45 PSI).. Failure: When U0074 is present due to FPCM communication loss, the actual fuel pressure may read significantly higher (e.g., 80-90 PSI) than the desired pressure because the FPCM defaults to maximum output.

Hidden / Shadow Codes Worth Checking

• U0074 00: The '00' is a GM symptom byte indicating a general 'bus off' state. It's the most common symptom byte for this code and confirms a total loss of communication on the bus rather than a more specific data error. (see via A professional scan tool like the GM GDS2/Tech2 or a high-end aftermarket scanner capable of reading manufacturer-specific data.)

Scan Tool Commands That Help

• GM GDS2 / Tech2: High Speed Communication / Device List — This is the first diagnostic step to see which modules on the network are actively communicating and which have dropped off. This helps isolate the source of the U0074 code by identifying the non-responsive module(s).
• GM GDS2 / Tech2: FPCM Fuel Pump ON/OFF — This bidirectional command is used to test the FPCM's ability to receive commands and activate the fuel pump. If the module is not communicating, this command will fail, confirming the communication breakdown.

Wiring & Ground Locations

• FPCM Connector — On the driver's side frame rail, typically near the rear of the driver's side passenger door.. This is the main connection point for the Fuel Pump Control Module, a primary cause of U0074. Key pins to test are Pin 13 (Dark Green/White) for the serial data enable signal from the ECM, and the CAN bus wires for communication.
• G103 / G104 — Grounds located on the cylinder heads at the rear of the engine. G103 is often on the passenger side head, G104 on the driver's side.. These are major engine grounds. A poor connection at G103 can affect the BCM, Instrument Panel Cluster, and DLC, all of which are critical for network communication.
• Frame Grounds (Front) — On the frame behind both front wheels.. These grounds are in a 'terrible location' highly susceptible to corrosion from tire splash, which can cause high resistance and lead to various electrical and communication faults.
• BCM Ground — Inside the cabin, near the A-pillar by the front left speaker. Requires removal of pillar and dash trim to access.. The Body Control Module (BCM) is a central hub for multiple data networks. A poor ground here can cause a wide range of bizarre electrical issues and communication codes.
• Terminating Resistors — The two 120-Ohm terminating resistors are typically not separate parts. One is internal to the Engine Control Module (ECM) and the other is internal to the Electronic Brake Control Module (EBCM).. A failure of either the ECM or EBCM can cause the total bus resistance to change from 60 Ohms to 120 Ohms, disrupting communication and setting a U0074 code.

Real Owner Repair Stories

• YouTube channel SteeveGMTECH (Chevrolet Suburban (sister platform to Yukon)) — Check Engine Light on with codes P2635, U0074, and P018B. Codes were hard faults and would not clear. Fuel gauge was inoperative. Scan tool showed actual fuel pressure was much higher (80-90 PSI) than desired pressure (46 PSI).
  ❌ Tried (didn't work) Initial diagnosis focused on the fuel pressure codes (P2635, P018B), which is a common misstep.
  ✅ What actually fixed it After consulting with GM technical assistance, the problem was identified as a loss of communication between the ECM and FPCM. All wiring and the FPCM were checked and found to be good. The final repair was the replacement of the Engine Control Module (ECM). After ECM replacement and programming, all codes cleared and the fuel gauge was restored.

OEM Part Supersession History

• 13534714, 13537053, 13544060, 13544950, 13545846 → 13554821 — Standard part evolution for improved reliability and to address known failure modes.