U0074 on 2014-2018 Chevy Silverado 2500: Causes and Fixes for Communication Bus Failure

What's Unique About the 2014-2018 Chevrolet SILVERADO 2500

The 2014-2018 Silverado 2500 range spans two truck generations, the GMT900 (2014) and the K2XX (2015-2018). On the newer K2XX platform trucks, U0074 is frequently caused by specific, well-documented wiring harness vulnerabilities. The harness that includes the communication wires for the Fuel Pump Control Module (FPCM) is known to chafe and corrode along the driver's side frame rail. Another extremely common chafe point, detailed in TSB 23-NA-074, is where the engine harness rubs against the sharp metal edge of the battery tray support bracket. This often leads to a U0074 code accompanied by fuel system codes like P2635, but the root cause is the communication failure, not the fuel pump itself.

Diagnostic Flowchart

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

Generation note: The specified year range covers two generations. The 2014 model year is the last of the GMT900 platform. The 2015-2018 models are the K2XX platform. While the code's meaning is the same, the most common cause—a chafed wiring harness near the FPCM or battery tray—is primarily documented on the 2015-2018 K2XX platform trucks. The GMT900 trucks also experience wire chafing, but may have different vulnerable locations.

Symptoms You May Notice

• Check Engine Light is on
• Vehicle may stall or not start
• No crank, no start condition
🎬 Watch: Troubleshooting a crank no start with no FPCM communication.
• "Service StabiliTrak" message
• "Service Power Steering" message
• Loss of power steering assist
• ABS and Traction Control lights on
• Fuel gauge may read empty or be inaccurate
• Harsh shifting or transmission stuck in one gear
🎬 Watch: Fixing shifting issues caused by damaged Silverado wiring.
• Multiple warning lights on the instrument cluster

Most Likely Causes

1. Chafed/Corroded Wiring Harness 🔴 High Probability On K2XX (2015-2018) models, the main chassis harness is routed along the driver's side frame rail and is susceptible to rubbing against brackets and the frame, especially near the FPCM and spare tire area. A second, highly documented chafe point is where the engine harness passes the sharp metal edge of the battery tray support bracket, as noted in TSB 23-NA-074. Other TSBs like 21-NA-149 also point to chafing near the ECM/TCM bracket, upper control arm, and shock tower.
   How to confirm: Visually inspect the entire length of the wiring harness on the driver's side frame rail. Pay close attention to any point where the harness makes contact with the frame or brackets. Remove the battery and battery tray to thoroughly inspect the harness for rubbing against the support bracket. Look for worn plastic conduit, exposed copper wires, and green corrosion.
   Typical fix: Repair the damaged wires. This involves cutting out the bad section, splicing in new wire, and protecting the repair with solder and heat-shrink tubing. The harness should then be re-routed or wrapped with anti-abrasion tape to prevent future damage. For the battery tray issue, TSB 23-NA-074 specifies applying anti-abrasion deadener material to the sharp bracket edge.
   Est. part cost: $10-$50
2. Failed Fuel Pump Control Module (FPCM) 🟡 Medium Probability → Shop Fuel Pump The FPCM is a critical node on a dedicated powertrain communication bus with the ECM. TSB #PIP5427B points to loss of communication between the ECM and FPCM as a direct cause. The module is mounted on the frame rail above the spare tire, exposing it to weather and vibration, which can lead to internal failure that brings down the network.
   How to confirm: After verifying the wiring is intact, use a scan tool to see if the FPCM is the only module not communicating. If so, disconnect the FPCM. If communication is restored to other modules on that bus, the FPCM is faulty. A technician in a YouTube video for a similar Suburban issue confirmed that if all wiring tests good, the ECM itself could be the culprit for not being able to communicate with the FPCM.
   Typical fix: Replace the Fuel Pump Control Module. The new module must be programmed to the vehicle using GM-specific software (SPS).
   Est. part cost: $80-$200
3. Poor Ground Connection ⚪ Low Probability Frame grounds are exposed to the elements and can corrode over time, creating high resistance that disrupts module operation and communication. Key grounds to inspect include G103 on the cowl, G218 under the driver's side dash, and G402/G405 at the rear of the frame near the FPCM and spare tire.
   How to confirm: Locate the main ground points for the chassis and engine. Disassemble, clean all contact surfaces to bare metal with a wire brush, and reassemble securely. A voltage drop test from the module's ground wire to the negative battery terminal is the definitive test for a bad ground.
   Typical fix: Clean or repair the ground connection points. This may involve replacing corroded ground straps or bolts.
   Est. part cost: $0-$20

Rare But Worth Checking

• Failed Termination Resistor: The CAN bus network has a 120-ohm resistor at each end. On these trucks, one is often internal to a module (like the EBCM) and the other is an external resistor taped to the harness, frequently located above the spare tire near the FPCM. If a resistor fails or its connection corrodes, communication is disrupted. This is confirmed by measuring ~120 ohms between pins 6 and 14 at the OBD-II port instead of the correct ~60 ohms.
• Aftermarket Electronics: Improperly installed remote starters, alarms, or audio equipment spliced into CAN bus wires can disrupt the network and trigger a U0074 code. Always check for aftermarket modifications first when diagnosing communication faults.
• Failed Control Module (Other than FPCM): Any module on the bus (EBCM, Power Steering Control Module, etc.) can fail internally and short out the communication lines. A diagnostic technique is to disconnect modules one by one while monitoring the bus with a scan tool or multimeter to see if communication is restored.

Diagnosis Steps

1. Check and charge the battery. Low voltage can cause numerous communication errors.
2. Use a professional scan tool to identify which control modules are not communicating. Note all DTCs.
3. Prioritize U0074 diagnosis over any other codes, especially P2635, as per TSB #PIP5427B.
4. Perform a thorough visual inspection of the main wiring harness along the driver's side frame rail, from the engine bay to the rear axle. Look for any signs of chafing, melting, or corrosion.
5. Remove the battery and battery tray. Inspect the harness for chafing against the sharp metal support bracket below it. This is a very common failure point.
6. Inspect the connectors at the Fuel Pump Control Module (FPCM), Electronic Brake Control Module (EBCM), and Engine Control Module (ECM) for corrosion or damage.
7. With the battery disconnected, measure the resistance between Pin 6 (CAN High) and Pin 14 (CAN Low) at the OBD-II port. A healthy network should read approximately 60 ohms. A reading of 120 ohms indicates an open circuit or a missing termination resistor. A reading near zero indicates a short circuit.
8. If wiring damage is found, repair the affected wires and protect the harness from future damage using anti-abrasion tape or loom.
9. If wiring and grounds are confirmed good, suspect a faulty module. Disconnect suspect modules (like the FPCM) one at a time to see if communication on the network is restored.

Parts You'll Likely Need

• Fuel Pump Control Module (OEM #23482933) — This module is a common failure point that can bring down the powertrain communication bus. It is often replaced after wiring issues have been ruled out. This part requires programming after installation.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $95-$180
  Aftermarket price range: $80-$140

Related Codes That Often Appear With This One

• P2635 — This code for 'Fuel Pump Flow Performance' is often set because the ECM has lost communication with the FPCM due to the U0074 fault. TSB #PIP5427B confirms this relationship.
• U18A2 — This is a more specific code for 'Lost Communication with Fuel Pump Control Module'. TSB #PIP5427B states that U0074 takes diagnostic priority if both are present.
• U0121 — Indicates 'Lost Communication With Anti-Lock Brake System (ABS) Control Module'. This can occur if the fault is on the chassis bus, which connects the EBCM.
• U0131 — Indicates 'Lost Communication with Power Steering Control Module'. This is common when the chassis bus is down, leading to the 'Service Power Steering' message.

Technical Service Bulletins (TSBs) & Recalls

• PIP5427B: Advises technicians to prioritize diagnosis of U0074 over fuel system codes like P2635, as the communication loss is the root cause. It notes this can cause fuel pressure to read substantially higher than desired.
• PIT5076E: Lists U0074 as a code that points to a fault on the 'Chassis bus' and requires network diagnosis.
• 23-NA-074: Details wire chafing on the battery tray support bracket as a specific cause for U0074 and many other codes on K2XX platform vehicles.
• 21-NA-149: General bulletin about multiple engine wiring harness chafe points on various GM trucks that can cause communication codes.

Platform-Specific Known Issues

• A known issue on 2015-2018 K2XX platform trucks is the engine/chassis wiring harness rubbing against a bracket near the battery tray or along the frame rail, causing a short in the communication circuit.
• TSB #PIP5427B specifically addresses U0074 in conjunction with P2635 and U18A2, noting that a loss of communication between the ECM and FPCM is the cause and that communication DTCs must be diagnosed first.
• TSB #21-NA-149 and #23-NA-074 detail multiple specific wiring harness chafe points on K2XX trucks, including against the ECM/TCM bracket, upper control arm, shock tower bolt, and battery tray support, all of which can cause U0074.

Mechanic-Grade Diagnostic Values

• High-Speed CAN Bus Resistance at DLC (Pins 6 & 14) — expected: ~60 Ohms (with battery disconnected). Failure: A reading of ~120 Ohms indicates an open circuit or a missing termination resistor. A reading near 0 Ohms indicates a short between the CAN High and Low wires.
• CAN High Voltage to Ground (Pin 6 at DLC) — expected: ~2.6V - 2.7V (Key On, Engine Off). Failure: Significant deviation, 0V, or being stuck high can indicate a short or open on the CAN High line.
• CAN Low Voltage to Ground (Pin 14 at DLC) — expected: ~2.3V - 2.4V (Key On, Engine Off). Failure: Significant deviation, 0V, or being stuck low can indicate a short or open on the CAN Low line.
• Powertrain Expansion Bus Resistance (at connector X125) — expected: ~120 Ohms when testing toward the ECM, and ~120 Ohms when testing toward the FPCM.. Failure: An open reading (OL) or a reading significantly different from 120 Ohms in either direction indicates a wiring break or a faulty termination resistor inside either the ECM or FPCM.

Hidden / Shadow Codes Worth Checking

• C710 symptom code 71: A manufacturer-specific symptom code that can be set in the electronic brake control module or power steering control module alongside U-codes like U0074, indicating a chassis bus fault. (see via This code is visible with a dealer-level scan tool like the GM GDS2/Tech2. It is mentioned in TSB #PIT5076E.)

Wiring & Ground Locations

• External Termination Resistor — Taped to the main wiring harness, often located above the spare tire near the Fuel Pump Control Module (FPCM).. This is one of the two 120-ohm resistors required for the CAN bus to function. If it fails, or the wiring to it breaks, the total bus resistance will incorrectly read 120 ohms instead of 60, causing communication to stop.
• X125 Connector — An inline harness connector located under the hood.. This connector is positioned between the ECM and the FPCM, providing a convenient access point to test the isolated Powertrain Expansion Bus for resistance and continuity without having to access the modules directly.
• G218 Ground — Located on the driver's side A-pillar, behind the plastic kick panel, under the dashboard.. This is a primary ground point for the Body Control Module (BCM). A poor connection here can cause a wide range of communication and electrical issues.
• ECM/TCM Bracket — The metal bracket holding the Engine and Transmission Control Modules in the engine bay.. TSBs identify the sharp edges of this bracket as a common point where the engine wiring harness can chafe, causing shorts in the CAN bus wires and triggering a U0074 code.

Real Owner Repair Stories

• iATN (International Automotive Technicians Network) Case Study (2015 Chevrolet Silverado 1500 4.3L V6) — Service Engine Soon light on, codes U0074, U18A2, and P2635 stored. Scan tool showed desired fuel pressure was low while actual fuel pressure was high.
  ❌ Tried (didn't work) Initial diagnosis pointed towards the FPCM, but the technician performed deeper electrical checks first.
  ✅ What actually fixed it The technician tested the dedicated bus between the ECM and FPCM at connector X125. Resistance tests showed both modules had intact 120-ohm terminating resistors. However, a voltage test revealed the ECM was outputting zero volts on the LAN circuit. The ECM itself had failed internally. Replacing and programming the ECM resolved all codes.
• SilveradoSierra.com forum user (2015 Silverado) — U0074, P2635, radio screen blank.
  ❌ Tried (didn't work) Replacing the Fuel Pump Control Module (FPCM).
  ✅ What actually fixed it A dealership technician found and repaired a single chafed wire in the main harness where it passes over the frame rail near the FPCM.
• YouTube video by 'Global Commerce CA' (2023 Chevrolet Silverado (demonstrates similar K2XX platform issue)) — U0074, U0103 (Lost comm with Gear Shift Module), no-shift condition after interior work.
  ❌ Tried (didn't work) Scanning for codes and initial visual inspection.
  ✅ What actually fixed it The fault was traced to a poor connection in a large inline wiring harness connector located under the passenger seat. Simply disconnecting and securely reconnecting the connector restored all communication and cleared the codes.

When the Usual Fixes Don't Work

• While wiring damage and a faulty FPCM are the most common culprits, a documented case showed that even with perfect wiring between the ECM and FPCM, the U0074 code was ultimately caused by an internal failure of the Engine Control Module (ECM). The ECM was not sending the required voltage signal to start communication on the dedicated bus. This highlights the need to test the entire circuit, including the source module, before replacing the non-communicating module.

OEM Part Supersession History

• 23103795, 23172742, 23200138 → 23482933 — Part revision and consolidation by the manufacturer.
  Heads up: Early 2014 models may use a different FPCM part number; VIN verification is critical when ordering.

Model Year Variations Within This Range

• 2015-2018 (K2XX Platform): These model years are highly prone to specific, documented wiring harness chafe points that are less common on the 2014 GMT900 platform. These include the harness rubbing on the battery tray support bracket and the ECM/TCM bracket.