U3007 — Control Module Input Power “B” #

The description of this diagnostic trouble code (DTC) may vary by OEM (Original Equipment Manufacturer). Always refer to your vehicle’s specific service information.

Known Label Variations:

• Control Module Input Power “B” (Generic/OEMs)
• Control Module Power Supply “B” Circuit (Ford, Lincoln, Mazda)
• Power Input to Control Module “B” (General Motors, Opel/Vauxhall)
• Module Voltage Supply “B” (Honda, Acura)
• ECU Input Power “B” (Toyota, Lexus)

Summary of Code U3007 #

U3007 is a network communication DTC that indicates a problem with the input power supply circuit—specifically, the “B” supply line—to one or more vehicle control modules. The “B” designation refers to a secondary power source or circuit, which may be critical for module operation, redundancy, or backup functions. When this DTC is set, the affected control module is either not receiving the correct voltage or is detecting voltage outside of normal parameters. As a result, this can cause intermittent operation, module shutdown, or erratic electrical behavior. Addressing this code promptly is important, as continued operation with unstable module power can lead to unpredictable vehicle behavior or further electrical damage.

Frequent Symptoms for Code U3007 #

The symptoms associated with U3007 can range from subtle electrical oddities to more pronounced system failures, depending on which module is affected and the nature of the power issue. Drivers might notice anything from warning lights to complete loss of certain vehicle functions. Common symptoms include:

• Multiple warning lights illuminated on the dashboard (ABS, traction control, airbag, etc.)
• Intermittent or total loss of function in affected systems (e.g., infotainment, climate control, advanced driver-assist systems)
• Failure to start or erratic engine operation
• Communication errors or network-related DTCs stored in other modules
• Battery drain or abnormal electrical consumption

Likely Causes for Code U3007 #

Because this code refers to the power supply circuit “B” for one or more control modules, its causes tend to involve electrical supply issues, either within the vehicle harness, connectors, or the module itself. The most frequent causes, in order, are:

1. Open, corroded, or loose connections at the module’s “B” power supply pin
2. Blown fuse or faulty relay in the “B” circuit
3. Damaged wiring harness (chafed, pinched, or shorted wires)
4. Internal module fault (rare but possible, especially if the module has an onboard power supply issue)
5. Low system voltage due to battery or alternator issues

Step-by-Step Diagnosis for U3007 #

Diagnosing U3007 requires patience and a methodical approach to pinpoint the exact source of the power interruption or anomaly. Here’s a professional step-by-step guide:

• Verify the code and note any other DTCs, especially those related to power or communication.
• Consult the OEM wiring diagram to identify the module and its “B” power supply path.
• Inspect the related fuse(s) and relay(s); replace if blown or faulty.
• Visually inspect the wiring harness for signs of damage, corrosion, or loose connections.
• Check for proper voltage at the module’s “B” power supply pin using a multimeter (key ON and during cranking if relevant).
• Wiggle test the connectors and harness while monitoring voltage and module operation.
• If power and ground are confirmed good but the DTC persists, suspect an internal control module fault and consider OEM-recommended module testing procedures.

Possible Repairs for U3007 #

Once the source of the issue is identified, repairs will be focused on restoring stable power to the affected control module. Based on the causes above, typical repairs include:

• Cleaning, tightening, or replacing electrical connectors at the module or in the power feed circuit
• Replacing blown fuses or faulty relays
• Repairing or replacing damaged wiring in the affected circuit
• Replacing the control module if diagnosed as internally faulty (after all power supply issues are eliminated)
• Repairing or replacing battery/alternator if system voltage is low

Is It Safe to Drive with Code U3007? #

Driving with U3007 is generally not recommended until the issue is corrected. Because this code involves the power supply to one or more control modules, continued driving can lead to unpredictable loss of critical vehicle functions—such as braking assist, stability control, or even engine operation. While the vehicle may appear to function normally at times, the risk of sudden module shutdown or erratic behavior is significant. For safety and reliability, address the root cause before further use.

Vehicles Most Commonly Affected by U3007 #

While U3007 is a generic network DTC, it is most frequently encountered on vehicles from manufacturers that use advanced networked control systems where separate power feeds are common. The following brands and models have reported this code more often:

• Ford (Focus, Escape, F-Series, Transit, Explorer)
• General Motors (Chevrolet Silverado, GMC Sierra, Buick Encore, Cadillac CTS)
• Mazda (Mazda3, CX-5, CX-9)
• Honda/Acura (Accord, Civic, CR-V, MDX, RDX)
• Toyota/Lexus (Camry, RAV4, Corolla, ES350)
• Opel/Vauxhall (Astra, Insignia, Corsa)

Common Mistakes & Best Practices with U3007 #

Misdiagnosing U3007 can lead to unnecessary parts replacement and extended downtime. Avoid these pitfalls and follow these best practices:

• Do not replace the control module before thoroughly checking the power supply and ground circuits.
• Always check for related fuses and relays—sometimes a simple blown fuse is the root cause.
• Consult the OEM wiring diagram; “B” power supply varies by vehicle and module.
• Check for corrosion or water intrusion, especially in vehicles exposed to harsh environments.
• Clear the code and retest after each repair step to confirm resolution.

U3007 Express FAQ #

A few quick answers to the most common questions about this DTC:

Q: Does U3007 always mean the control module needs replacing?
A: No. Most U3007 cases are due to external power supply issues—fuses, wiring, connectors. Only replace the module if all power and ground checks pass and the fault is still present.

Q: Can a weak battery trigger U3007?
A: Yes. Low system voltage can cause modules to lose their power supply reference, setting this code. Always check battery health as part of your diagnosis.

Q: Is U3007 related to CAN bus or network problems?
A: Indirectly. This code indicates a power issue, but if a module loses power, it can drop off the network, leading to additional communication DTCs. Resolve the power issue first.