U0064 – Propulsion CAN, General fault information, No sub-type information

U0064 means a control module has detected a fault on the propulsion CAN network. In plain English, modules that manage engine, transmission, hybrid, or drive torque information are not communicating normally, so the vehicle may show multiple warning lights, lose certain functions, or act unpredictably. According to SAE J2012-DA wording, this code only identifies a general propulsion network problem, not a failed part. That vagueness is intentional. The real fault may involve wiring, connectors, power or ground loss at a module, or a module that disrupts network traffic. Proper testing must identify which network segment or module caused the fault.

U0064 Quick Answer

U0064 points to a general communication fault on the propulsion CAN bus. Start by checking which modules communicate, then verify network wiring, connector condition, and module power and ground before replacing anything.

What Does U0064 Mean?

U0064 is defined as Propulsion CAN, General fault information, No sub-type information. That means one module detected a problem on the network used by propulsion-related controllers. In practice, the vehicle may lose data sharing between the ECM, TCM, hybrid control module, inverter control, or other torque-related modules. The code does not tell you which module failed. It tells you the network path or one participant on that network needs diagnosis.

Technically, the module monitors whether expected CAN communication remains valid on the propulsion bus. It watches message timing, bus availability, and message integrity. If the module sees an abnormal network condition, but cannot classify it as a more specific high, low, open, or performance subtype, it can set U0064. That matters because the code reflects a suspected trouble area. It does not prove a bad ECM, TCM, or other controller.

Theory of Operation

Under normal conditions, propulsion-related modules share fast data over the CAN network. They exchange torque requests, throttle position, engine speed, transmission status, traction reduction commands, and other operating information many times per second. Each module relies on stable bus voltage behavior, correct message timing, and clean power and ground feeds. When that network stays healthy, the modules coordinate drivability, emissions, shifting, and sometimes hybrid propulsion without delay.

U0064 sets when that normal message exchange breaks down in a general way. A shorted CAN circuit, high resistance in a splice, water intrusion in a connector, or a module that drops off the bus can all cause it. So can weak module power or ground. On some vehicles, one failing propulsion controller can hold the bus busy or corrupt traffic for every other module. That is why network scan results, module presence, and power and ground checks come before any module replacement.

Symptoms

U0064 symptoms vary by platform, but the pattern usually points to a propulsion network communication problem rather than a single failed sensor.

• Scan tool communication issues: One or more propulsion-related modules may not appear on the module list, or communication may drop out during a full vehicle scan.
• Multiple warning lights: The malfunction indicator lamp, transmission warning, traction control light, hybrid warning, or reduced power message may appear together.
• No-start or delayed start: The engine may crank but not start if the ECM cannot exchange required authorization or torque data.
• Reduced power operation: The vehicle may enter limp mode because modules cannot trust torque and drivetrain messages.
• Harsh shifting or fixed gear operation: The transmission may default to backup strategy when network data from the engine or drivetrain goes missing.
• Intermittent drivability complaints: The driver may report sudden loss of throttle response, erratic power delivery, or brief stalling events.
• Additional network or module codes: You may also find other U-codes, lost communication faults, or module-specific performance codes stored as current or history faults.

Common Causes

• Loss of power or ground to a propulsion-network module: A module that loses stable voltage or ground can drop off the Propulsion CAN and trigger a general network fault without identifying a specific failed part.
• Open circuit in a Propulsion CAN wire: A break in CAN high or CAN low interrupts message flow between powertrain-related modules and sets U0064 when expected communication no longer matches network activity.
• Short to ground, short to voltage, or short between CAN circuits: A wiring short distorts bus bias voltage and message integrity, which can disrupt the entire propulsion communication segment.
• Corroded, loose, or spread terminal connections: Terminal tension loss or corrosion adds resistance and creates intermittent communication dropouts, especially during vibration, heat soak, or high current events.
• Harness damage near engine or transmission components: Heat, oil saturation, bracket chafing, or previous repair damage can expose the network pair and cause intermittent or hard Propulsion CAN faults.
• One module pulling the bus down: An internally faulted control module can load the network and prevent other modules from transmitting valid messages even though the code itself does not confirm which module caused it.
• Poor splice pack or gateway connection: Many propulsion-network circuits join through shared splices or gateway points, and high resistance there can affect multiple modules at once.
• Low system voltage during crank or charging faults: Weak battery voltage or unstable charging can force modules offline and create communication errors that appear as a network problem rather than a direct battery complaint.

Diagnosis Steps

You need a capable scan tool with full network scan, wiring diagrams, a quality DVOM, and access to connectors for the affected bus. A lab scope helps with intermittent faults, but basic network checks still start with freeze frame, module presence, fuse feeds, and voltage-drop testing under load. For U0064, note vehicle speed, ignition state, and all related DTCs before touching the harness.

1. Confirm U0064 with a full-system scan. Record whether the code shows as pending, confirmed, current, or history. Save freeze frame data, especially ignition state, vehicle speed, battery voltage, and any companion network or low-voltage DTCs. Freeze frame shows conditions when the code set. A scan tool snapshot helps later if the fault appears only during a road test.
2. Run the network scan and note which modules communicate and which do not. On a communication code, this step comes before meter work. Also inspect power distribution basics right away. Check related fuses, relay feeds, and shared module supplies for the propulsion network before measuring at any module connector.
3. Verify battery condition and charging performance if the scan data or customer complaint suggests low voltage. Then test power and ground to any missing or suspect module under load, not with a simple unloaded voltage check. Measure ground voltage drop with the circuit operating. Keep ground drop below 0.1 volt. High resistance often hides during continuity checks.
4. Inspect connectors and the harness along the Propulsion CAN path. Focus on areas near the ECM, TCM, hybrid control hardware if equipped, battery junctions, transmission case routing, and known rub points. Look for backed-out terminals, moisture, green corrosion, pinch damage, aftermarket splices, and twisted-pair untwisting from prior repairs.
5. With ignition off and the battery disconnected, measure resistance between CAN+ and CAN- at an accessible module connector or DLC if that path applies on the vehicle. A healthy high-speed CAN bus usually reads about 60 ohms. If you see about 120 ohms or OL, suspect an open circuit or a missing terminating path. If the reading is very low, suspect a shorted bus or a module loading the network.
6. Reconnect the battery and turn ignition on. Measure CAN+ and CAN- bias voltage to ground on the affected network while powered. On a healthy idle bus, both lines usually sit near 2.5 volts to ground. Ignition-off readings do not count because the bus bias is not valid when the network is asleep.
7. If resistance or bias voltage looks wrong, isolate the faulted branch. Disconnect accessible modules on the propulsion network one at a time, following the wiring diagram and safe service information. Watch for the 60-ohm reading or normal bias voltage to return. That pattern often identifies a shorted module or a branch with damaged wiring.
8. If resistance and bias voltage look normal, move to dynamic checks. Wiggle the harness at engine movement points, fuse blocks, and connector transitions while monitoring module communication on the scan tool. If available, use a scope to compare bus activity during the wiggle test. Intermittent U0064 faults often show up here.
9. Review companion DTCs closely. A specific lost-communication code, power supply code, ignition feed code, or module internal fault often points to the network participant creating the general U0064 complaint. Do not replace the first module that drops offline until you verify its power, ground, and CAN path.
10. After repairs, clear codes and repeat the network scan. Confirm all expected propulsion modules report normally. Then road test the vehicle under the same conditions found in freeze frame. Recheck for pending and confirmed codes. A hard communication fault usually returns quickly on key-on, while an intermittent fault may need vibration, heat, or load to show itself.

Professional tip: On U0064, the module setting the code often reports only that the propulsion network behaved abnormally. It may not be the failed node. If one control unit will not communicate, prove its fuse feed, loaded ground, and CAN integrity first. That step prevents expensive, incorrect module replacement and comebacks.

Possible Fixes

• Repair power or ground feed faults to the affected module: Restore proper fuse feed, relay output, or ground path after voltage-drop testing confirms excess resistance or intermittent supply loss.
• Repair open or shorted CAN wiring: Fix damaged twisted-pair sections, remove poor splices, and restore proper routing and shielding where harness damage disrupted bus communication.
• Clean, tighten, or repin corroded connectors: Correct terminal drag issues, corrosion, or backed-out pins when connector inspection and wiggle testing identify unstable network contact.
• Repair shared splice or junction faults: Rebuild compromised splice packs, gateway connections, or junction blocks when multiple propulsion modules lose communication through a common point.
• Correct battery or charging system problems: Replace a failing battery or repair charging faults if low system voltage causes modules to reset or drop off the Propulsion CAN.
• Replace and program a confirmed failed module: Only replace a control module after you verify correct power, ground, network integrity, and branch isolation prove the module itself loads or corrupts the bus.

Can I Still Drive With U0064?

You might be able to drive with U0064, but you should not assume the vehicle is safe or fully functional. This code points to a fault on the propulsion CAN network, which supports powertrain communication between critical modules. Some vehicles only store the U0064 code and keep driving normally. Others enter reduced-power mode, limit shifting, disable start-stop, or set multiple warning messages. If the engine stalls, the transmission shifts harshly, or the vehicle loses throttle response, stop driving and diagnose it first. Treat U0064 as a network fault that can change from nuisance to drivability problem without warning, especially when heat, vibration, or moisture affect the wiring or connector involved.

How Serious Is This Code?

U0064 ranges from moderate to severe, depending on which propulsion network messages drop out and how often the fault occurs. At the mild end, it acts like an inconvenience. You may only see warning lights, stored communication codes, or an occasional no-response module on a scan tool. At the serious end, the vehicle can lose coordinated control between the ECM, transmission control module, hybrid control module, or other propulsion-related controllers. That can trigger limp mode, no-start, erratic shifting, or unstable drivability. Ignoring the code can turn a small wiring issue into repeated network failures, hard faults, and misdiagnosed module replacement. Diagnose it promptly, especially if the problem appears during acceleration, gear changes, or hot soak conditions.

Common Misdiagnoses

Technicians often replace a module too early when U0064 appears with several other U-codes. That wastes money because a network fault usually starts with lost communication quality, not a proven failed controller. Another common mistake is checking CAN resistance with the battery disconnected, then stopping there. A static resistance check will not expose a loaded power feed, weak ground, water intrusion, or an intermittent splice problem. Shops also miss the difference between a module that is offline and a module that is present but reporting network errors. The correct path starts with a full network scan, module presence check, and loaded power and ground testing before any controller replacement or programming decision.

Most Likely Fix

The most common U0064 repair direction is restoring network integrity at a propulsion-related connector, splice, power feed, or ground that fails under load. Corrosion at a CAN junction, backed-out terminals, or harness damage near heat and vibration points often causes this code. Another frequent repair path involves correcting a module power or ground issue that makes one controller drop off the bus and disrupt propulsion communication. After repair, confirm the fix with a complete network scan, road test, and the exact enable conditions that let the affected module run its communication checks. Those conditions vary by platform, so service information matters.

Repair Costs

Network and communication fault repairs vary by root cause — wiring/connectors are often the source, but module-level repairs or replacements can be significantly more expensive.

Last updated: April 11, 2026