U3015 — Control Module Input Power B Circuit High

What are the symptoms of U3015?

Drivers most often notice: multiple warning lights on at once, no-start or intermittent starting in some cases, random, hard-to-reproduce electrical glitches, intermittent loss of functions (gauges, windows, steering assist).

How much does it cost to fix U3015?

Remove interfering aftermarket device — $0–$150; Replace the faulty control module — $300–$1,500; Repair CAN wiring or connectors — $100–$400. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Is it safe to drive with U3015?

Depends on what is affected. A single dead convenience module is fine to drive with; loss of communication with engine, braking or steering modules is not. If multiple critical systems drop out, do not drive.

What does OBD2 code U3015 mean?

OBD2 code U3015 flags a problem with the vehicle network (CAN bus) communication (U3015 - control module input power b circuit high). Short, gentle driving to a shop is usually possible. Common culprits: damaged CAN bus wiring or short to power/ground, poor grounds or low battery voltage, water ingress in harness junctions.

Will U3015 clear itself?

Sometimes U3015 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What does U3015 mean?

U3015 (U3015 - Control Module Input Power B Circuit High) is stored when self-diagnostics detect abnormal readings or behaviour of the vehicle network (CAN bus) communication. It belongs to the vehicle category.

“Circuit high” means the control module sees a voltage on the U3015 - control module input power b circuit that is above the expected range — typically close to battery voltage. Physically this points to a short to a power feed, a broken ground return, or a failed component pulling the signal line high.

This code does not appear from a single bad reading: the module must see the fault condition repeat under defined operating conditions before it turns on the warning light. The freeze frame captured with U3015 — engine load, rpm, temperature, speed — tells you exactly when the problem occurs, so reproduce those conditions when testing.

Common symptoms of U3015

• multiple warning lights on at once
• no-start or intermittent starting in some cases
• random, hard-to-reproduce electrical glitches
• intermittent loss of functions (gauges, windows, steering assist)
• modules intermittently not communicating with the scanner

What causes U3015?

• open ground return of the U3015 - control module input power b
• failed U3015 - control module input power b pulling the signal high
• signal wire shorted to battery positive
• aftermarket equipment interfering with the bus
• poor grounds or low battery voltage
• damaged CAN bus wiring or short to power/ground
• water ingress in harness junctions

How to diagnose U3015

1. Connect an OBD2 scanner, confirm U3015 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
2. Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many U0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
3. Visually inspect the wiring harness and connectors related to the vehicle network (CAN bus) communication for damage, corrosion, chafing or poor contact.
4. With the U3015 - control module input power b disconnected, measure signal voltage at the harness connector: a high reading with the component unplugged indicates a short to power in the harness; if it drops to normal, the component itself is faulty.
5. Measure resistance between CAN-High and CAN-Low at the OBD port with power off — about 60 Ω is healthy.
6. Scan all modules: the one that does not respond is either the culprit or downstream of the break.
7. Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm U3015 does not return.

How to fix U3015

Start with the cheapest and most common causes before replacing expensive parts:

• Remove interfering aftermarket device — $0–$150
• Replace the faulty control module — $300–$1,500
• Repair CAN wiring or connectors — $100–$400

How much does it cost to fix U3015?

Repair cost depends on which component actually failed. Typical scenarios for U3015 (parts and labor, USD, independent shop rates):

• Remove interfering aftermarket device: $0–$150
• Replace the faulty control module: $300–$1,500
• Repair CAN wiring or connectors: $100–$400

Overall, fixing U3015 usually costs between $0 and $1,500. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can you drive with U3015?

Depends on what is affected. A single dead convenience module is fine to drive with; loss of communication with engine, braking or steering modules is not. If multiple critical systems drop out, do not drive.

Related OBD2 codes

• U3000: Control Module
• U3001: Control Module Improper Shutdown
• U3002: Vehicle Identification Number
• U3003: Battery Voltage
• U3004: Accessory Power Relay
• U3005: Retained Accessory Power