U3007 on 2021 Jeep Wrangler: Causes and Fixes for Control Module Power Issues

What's Unique About the 2021-2021 Jeep WRANGLER

The 2021 Jeep Wrangler (JL generation) uses a complex dual-battery system to manage its electrical load and the Engine Stop-Start (ESS) feature. A main battery provides starting power, while a smaller auxiliary battery powers the vehicle's electronics when the engine is off at a stop. These batteries are connected in parallel most of the time. This auxiliary battery is a frequent point of failure and a primary cause for low voltage conditions that trigger code U3007 and other related electrical faults. When the auxiliary battery fails, it creates a parasitic drain on the main battery, often leading to a no-start situation and a cascade of error codes.

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 or MIL) is on.
• "Service Engine Stop/Start (ESS) System" message on the dashboard.
• Remote start fails to work.
• Unusual and seemingly random error messages, such as "Water in Fuel", "Service Shifter", or "Service Airbag System".
• Vehicle may not start and require a jump.
• Electrical accessories like the radio, auxiliary switches, or power steering may be unavailable or act erratically.
• Horn chirp when locking the vehicle sounds weak.
• Instrument cluster may display nonsensical readings or warnings, like the odometer reading "999999".

Most Likely Causes

1. Failing Auxiliary Battery 🔴 High Probability → Shop Vehicle Battery The factory-installed auxiliary batteries in JL Wranglers are known to have a relatively short service life, often failing within 2-4 years. Their failure is the most common trigger for a cascade of low-voltage DTCs, including U3007.
   How to confirm: Test the auxiliary battery's voltage at rest after isolating it from the main battery; a reading below 12.4V indicates it is failing. A professional load test is the most definitive method. Often, the first sign is the ESS system becoming unavailable with a "battery charging" message.
   Typical fix: Replace the auxiliary battery. 🎬 See this easy shortcut for replacing the auxiliary battery. It is strongly recommended to replace the main battery at the same time, as a failing auxiliary battery will damage the main one by constantly draining it.
   Est. part cost: $100-$180
2. Failing Main Battery 🟡 Medium Probability → Shop Vehicle Battery A failing main battery can cause a general low-voltage condition throughout the vehicle, triggering power input codes for various modules. The dual-battery system's health is interconnected; a bad main battery can be caused by a bad auxiliary battery, or it can fail on its own.
   How to confirm: Perform a load test on the main battery after disconnecting it from the auxiliary. Voltage should be approximately 12.6V at rest and should read above 14V when the engine is running, indicating a healthy alternator.
   Typical fix: Replace the main battery. This is often done in conjunction with replacing the auxiliary battery as a set.
   Est. part cost: $200-$400
3. Loose or Corroded Battery Terminals/Grounds ⚪ Low Probability → Shop Vehicle Battery
   How to confirm: Visually inspect all battery terminals, main power cables, and chassis ground straps for tightness and any signs of corrosion. Pay close attention to the smaller wires on the negative terminal array near the fuse box.
   Typical fix: Clean the terminals and cable ends with a wire brush and ensure all connections are secure.
   Est. part cost: $1-$10

Rare But Worth Checking

• Blown Fuse: A fuse protecting the specific module's 'B' power circuit could be blown. This is often a symptom of another problem, like a short circuit, but is a simple check. Some owners attempting to bypass a bad auxiliary battery by pulling fuse F42 may experience other issues if not done correctly.
• Wiring Harness Fault: A wire in the harness that provides power to the affected module could be broken, chafed, or shorted to ground. This requires diagnostic time with a multimeter and wiring diagrams to trace. This is an uncommon cause for this specific code on this platform.
• Faulty Control Module: The module itself could have an internal fault. This is the least likely cause and should only be considered after all power and ground circuits have been confirmed to be good. The 4xe models, in particular, have multiple control modules (IDCM, BPCM, EVCU) that can be affected by low voltage conditions.

Diagnosis Steps

1. Read all Diagnostic Trouble Codes (DTCs) from all vehicle modules using an OBD-II scanner.
2. Check the static voltage of both the main and auxiliary batteries. A healthy, fully charged battery should read around 12.6 volts. Readings of 12.2V or lower after sitting are a strong warning sign.
3. Start the engine and check the charging system voltage via the dashboard display or a multimeter. It should be between 13.7 and 14.7 volts (often around 14.1-14.4V).
4. If voltage is low, disconnect the batteries from each other. This typically involves removing the negative terminal connections at the main fuse box. Then, perform a professional load test on both the main and auxiliary batteries individually. This is the most critical step.
5. Inspect all battery terminals and main ground connections for corrosion and tightness.
6. If batteries and connections are good, consult a wiring diagram for the specific module logging the U3007 code to test the 'B' power input circuit for voltage and continuity.
7. Check the fuse related to the affected circuit in the Power Distribution Center (fuse box).

Parts You'll Likely Need

• Auxiliary Battery (OEM #56029759AB, 68647042AA) — This is the most frequent failure point on 2021 Wranglers that leads to code U3007 and a host of other electrical issues.
  Trusted brands: Mopar, Duralast (e.g., AUX14), Odyssey, Duracell (e.g., Group 401)
  OEM price range: $150-$200
  Aftermarket price range: $100-$150
• Main Battery (AGM Type) — Often fails along with, or as a result of, a failing auxiliary battery. It is best practice to replace both at the same time 🎬 Watch: Step-by-step guide to replacing both batteries on your Wrangler. to prevent the old battery from damaging the new one.
  Trusted brands: Mopar, Optima, Duralast, Odyssey
  OEM price range: $250-$350
  Aftermarket price range: $200-$300

Related Codes That Often Appear With This One

• C2100-00 — This code for 'Battery Voltage Low' is a direct indicator of the low voltage condition causing U3007.
• U3006-00 — This code for 'Control Module Input Power 'A' Circuit/Open' often appears with U3007, indicating a widespread power loss to a module.
• C05A4-00 — 'Wheel Speed Sensors Supply Circuit Low' is another code triggered by the system-wide low voltage from a failing battery.
• B2199-16 — 'Battery Voltage-Circuit Voltage Below Threshold' is another common companion code pointing directly to a battery issue.

Technical Service Bulletins (TSBs) & Recalls

• 08-106-21 Rev. A: Addresses MIL illumination due to low battery charge, specifically listing U3007, C2100-00, U3006-00, and B2199-16 as potential codes. The fix involves testing and possibly replacing the 12V battery for vehicles built before a specific date in March 2021.

Platform-Specific Known Issues

• Real Owner Experience: On the JLWranglerForums, a user described their 2021 Wrangler failing to restart at a red light. After a jump start, it later failed to cold start, and upon a second jump, lost power steering and displayed numerous warnings before losing all electrical power. They replaced the main battery with no success, then learned about the auxiliary battery. After replacing the auxiliary, the engine had a rough idle and displayed a "pull over the vehicle will shut off shortly" message, which it did. This highlights the cascading failures that can occur and the importance of addressing both batteries.
• TSB 08-106-21 Rev. A: Jeep issued Technical Service Bulletin (TSB) 08-106-21 Rev. A, which directly addresses code U3007 along with other low-voltage DTCs. The procedure involves testing and potentially replacing the 12V battery on vehicles built on or before March 22, 2021. This was also released as a Rapid Response Transmittal (RRT) 21-077, indicating a higher priority for service centers.

Mechanic-Grade Diagnostic Values

• Intelligent Battery Sensor (IBS) Quiescent Current — expected: [-500mA, 50mA]. Failure: Current draw outside this range prevents the vehicle from entering a 'sleep' state, which is required for the IBS to calibrate the battery's State of Charge (SOC).

Hidden / Shadow Codes Worth Checking

• Code 'Flood': A low voltage event from a failing dual-battery system often does not set just one code, but a 'flood' of communication (U-series) codes across many unrelated modules (e.g., ABS, shifter, radio, airbag). The diagnostic pattern itself—a long list of communication faults—is the key indicator of a systemic power supply issue, rather than a single hidden code. (see via A capable OBD-II scanner that can read codes from all vehicle modules, not just the PCM.)

Scan Tool Commands That Help

• Procedural (No scan tool required): Intelligent Battery Sensor (IBS) Reset and Relearn — This procedure is mandatory after replacing either the main or auxiliary battery, or after a complete power disconnect. The IBS measures the battery's state of charge, and failure to reset it will lead to improper charging and a cascade of electrical warnings. The reset forces the sensor into a relearn process. The relearn process requires 5 normal, operator-initiated starts with at least eight hours of 'off' time between each start to complete.

Wiring & Ground Locations

• CAN Bus Star Connector — Located behind the glove box, mounted to a rail. The glove box must be opened and dropped down to access it.. This is a central hub where many of the vehicle's control module communication lines connect. A poor connection or internal fault (due to cracked solder joints) in this connector can cause a loss of communication between modules, generating a flood of U-codes, including U3007, and mimicking the symptoms of a battery failure.
• G901A / G902A — Main battery ground points in the engine bay.. These are the primary ground connections for the entire vehicle electrical system. Corrosion or looseness here can cause widespread voltage issues and trigger power input codes like U3007.
• G906A / G906B — Dash harness ground points, located in the driver and passenger footwell areas.. These grounds are critical for the numerous control modules located within the dashboard and cabin. A fault at these points can affect specific modules and trigger targeted power codes.

Real Owner Repair Stories

• JLWranglerForums user (Jeep Wrangler JL) — A host of intermittent electrical issues including loss of power steering, limp mode, and multiple warning lights.
  ❌ Tried (didn't work) Initial diagnosis pointed towards battery or alternator issues.
  ✅ What actually fixed it The issue was traced to the CAN bus star connector behind the glove box. Wiggling the second or third connector on the block would temporarily resolve all symptoms. The final fix was to replace the star connector block itself.

"I Checked Everything" — The Actual Cause

• In cases where both batteries test healthy and all main ground connections are clean and tight, the root cause can be a faulty CAN bus star connector located behind the glove box. This central communication hub can develop internal faults, such as cracked solder joints, leading to intermittent communication loss between modules. This will not be found with a smoke test or standard power/ground checks, but can sometimes be identified by wiggling the connectors while the vehicle is malfunctioning to see if symptoms change.

When the Usual Fixes Don't Work

• While the overwhelming majority of U3007 cases on this platform are caused by the dual-battery system, there are documented instances where the batteries are not at fault. A notable alternative cause is a failure of the CAN bus star connector, a central wiring hub located behind the glove box. One owner reported experiencing a cascade of electrical failures, including loss of power steering and multiple warning lights. After confirming the batteries were good, the problem was traced to a loose or faulty connection within this star connector. Simply wiggling the connectors temporarily resolved the issue, with a full replacement of the connector block being the permanent fix. This highlights a critical diagnostic path for when the common battery fix does not work.

OEM Part Supersession History

• 68321746AA → 68230877AA (13-way connector) — The original 20-way star connector (68321746AA) is often substituted with the 13-way version (68230877AA) in newer models or as a replacement part due to availability.
  Heads up: The connectors are physically different (20-pin vs 13-pin), but the individual module plugs can be transferred over. Functionally, they serve the same purpose as a communication junction.

Model Year Variations Within This Range

• 2021 and later: The configuration of the two main negative cables attached to the Intelligent Battery Sensor (IBS) was reversed. On 2021+ models, the top cable is the larger main battery ground, while the lower cable with a stud is the auxiliary battery ground. This is the opposite of prior years and is critical to know when isolating the batteries for testing or charging.