Subaru U1500 & B1500 on 2012-2016 Impreza: Keyless Entry Communication Failure Explained

What's Unique About the 2012-2016 Subaru Impreza

The key challenge with this code on a 2012-2016 Impreza is correctly identifying it. Many online databases may incorrectly list U1500 for the Impreza, leading to confusion. However, Subaru's official documentation makes a clear distinction: B1500 is for the Impreza/Crosstrek/Forester, and U1500 is for the WRX/STI of the same era for this specific keyless communication fault. This guide addresses the underlying problem—a keyless communication failure—which is the root of both codes, but focuses on the B1500 code as the one owners will actually find.

Symptoms You May Notice

• Remote keyless entry (door locks) does not work, even with a new key fob battery.
• Security light may behave erratically or stay illuminated.
• In rare cases, a no-start condition if the immobilizer system is affected, which points more towards a BIU failure than the keyless module itself.
• Power lock switch on the door may also be inoperative.

Most Likely Causes

1. Faulty Keyless Entry Control Module 🔴 High Probability → Shop Keyless Entry Module Internal failure of the module is a common endpoint in the diagnostic procedure outlined by Subaru. This module is the receiver for the key fob signals.
   How to confirm: After verifying all wiring and connectors are good, the final diagnostic step in TSB 07-83-14 is to substitute a known-good keyless entry control module. The module is typically located in the rear of the vehicle, behind the quarter trim panel. 🎬 Watch: How to access and remove the keyless receiver A user on a Subaru forum confirmed that a used module from a junkyard is not VIN-locked and can work, making this a viable DIY test.
   Typical fix: Replace the keyless entry control module. The module itself is plug-and-play, but the key fobs will need to be reprogrammed to the new module. 🎬 Watch: How to program Subaru keys without a dealer
   Est. part cost: $60-$150
2. Wiring Harness or Connector Issue 🟡 Medium Probability The communication (UART) circuit runs between the BIU and the keyless module. Any damage, corrosion, or loose connection along this path will cause the fault. Connectors to either module can develop poor contact.
   How to confirm: Inspect and test the harness connectors for the BIU and keyless entry module for good contact. Perform resistance and voltage checks on the communication, power, and ground wires as detailed in the service manual or TSB 07-83-14. A resistance of 10 Ω or less is expected on the ground circuit.
   Typical fix: Repair the damaged section of the wiring harness or clean/replace the faulty connector.
   Est. part cost: $10-$100
3. Faulty Body Integrated Unit (BIU) ⚪ Low Probability → Shop Body Control Module The BIU is the master controller for this system. While less common to fail than the keyless module, an internal BIU fault can cause this code and a host of other electrical gremlins.
   How to confirm: This is typically diagnosed by exclusion. If all wiring and the keyless entry module have been proven to be good, the BIU is the remaining point of failure. Symptoms of a failing BIU often include multiple, unrelated electrical issues.
   Typical fix: Replace the Body Integrated Unit. This is a complex job as the new BIU must be programmed to the vehicle's immobilizer system and keys. A Reddit user with a 2016 Crosstrek reported a dealer quote of over $2,000 for this job because they did not have the third key registered to the car, requiring the ECU and BIU to be sent to Subaru headquarters. Mail-in 'cloning' services exist that can copy data from the old BIU to a donor unit, potentially avoiding dealer programming.
   Est. part cost: $400-$700

Diagnosis Steps

1. Confirm the code using a scan tool capable of reading Subaru body codes. Expect to find B1500 for a keyless entry communication fault.
2. Differentiate from other issues. If the main symptom is an inaccurate fuel gauge, investigate the fuel level sensor system under TSB 09-63-16 instead.
3. Per TSB 07-83-14, check for poor contact at the Body Integrated Unit (BIU) and Keyless Entry Control Module connectors. The keyless module is often in the trunk/hatch area behind the trim.
4. Inspect the wiring harness between the BIU and the keyless module for any visible damage, chafing, or corrosion.
5. Check the power supply and ground circuits for the keyless entry control module using a multimeter to ensure they meet specifications. The power supply should be 10V or more, and the ground circuit should have less than 10 Ω of resistance.
6. If wiring, power, and ground are all confirmed to be good, the fault is likely with a control module. The next step is to replace the Keyless Entry Control Module. A used module may be sourced, as it is not VIN-locked.
7. If a new Keyless Entry Control Module does not resolve the issue, the Body Integrated Unit (BIU) is the most likely remaining cause. Note that a replacement BIU requires programming by a dealer or a specialized shop with tools like the Subaru Select Monitor. Alternatively, consider a mail-in cloning service to transfer data from your old BIU to a compatible donor unit.
🎬 See how to program a Subaru Body Integrated Unit

Parts You'll Likely Need

• Keyless Entry Control Module (OEM #88035-FJ020 (Verify by VIN)) — This module is a common failure point that leads to the B1500 communication code. It acts as the receiver for the key fobs.
  Trusted brands: Subaru (OEM)
  OEM price range: $60-$150
• Body Integrated Unit (BIU) (OEM #Varies by year/trim (e.g., 82201FJxxx). Must be matched exactly.) — This is the master body computer. It is the cause if all other components and wiring check out. Replacement requires professional programming. A failure here can cause many random electrical problems.
  Trusted brands: Subaru (OEM)
  OEM price range: $400-$700

Technical Service Bulletins (TSBs) & Recalls

• 07-83-14: 'Diagnostics for DTC B1500 and U1500' - This TSB is the definitive source, clarifying that B1500 applies to the Impreza for keyless communication failure, while U1500 applies to the WRX/STI. It also provides the full diagnostic procedure.
• 09-63-16: 'DTC B1500 and/or Inaccurate Fuel Gauge' - This TSB addresses the *other* use for code B1500 on this platform, which relates to a fuel level sensor fault. This is a critical document for avoiding misdiagnosis.

Platform-Specific Known Issues

• Real-World BIU Replacement Nightmare: A 2016 Subaru Crosstrek (platform mate) owner on Reddit shared their experience with a BIU replacement. The dealer quoted $810 initially, but the cost ballooned to over $2,000 because a third, unaccounted-for key was registered to the vehicle. The dealer claimed they needed all registered keys to program the new BIU and that the only alternative was to ship the BIU, ECU, and combination meter to Subaru for a data wipe, incurring massive extra cost and time. This highlights the critical importance of having all keys present for any BIU-related programming.

Mechanic-Grade Diagnostic Values

• Keyless Entry Module Power Supply Voltage — expected: 10 Volts or more. Failure: A reading below 10V indicates a problem in the power supply circuit.
• Keyless Entry Module Ground Circuit Resistance — expected: 10 Ω or less. Failure: A reading above 10 Ω indicates a poor ground connection or an open in the ground circuit.
• UART Communication Line Continuity — expected: Continuity (low resistance) between BIU connector and Keyless Entry Module connector.. Failure: High or infinite resistance (OL) indicates an open circuit in the harness.

Scan Tool Commands That Help

• Subaru Select Monitor (SSM): Read DTC from Body Integrated Unit — This is the first step to confirm if B1500 is the active code stored in the BIU.
• Subaru Select Monitor (SSM): Clear Memory (Keyless Entry) — After a repair is performed, this function is used to clear the stored fault code before re-testing the system.
• Subaru Select Monitor (SSM): Immobilizer Registration — This function is mandatory when replacing the Body Integrated Unit (BIU) to register the new module to the vehicle's immobilizer system and keys.
• Subaru Select Monitor (SSM): Current Data Display & Save — Allows viewing of live data from the BIU, such as 'IG power supply voltage', which is useful for diagnosing power-related issues to the module without manual probing.

Wiring & Ground Locations

• Body Integrated Unit (BIU) — In the driver's side footwell, located up under the dashboard near the interior fuse panel.. This is the master module where the B1500 code is stored. Physical access is needed to test its connector (i171) or to replace it.
• Keyless Entry Control Module — Typically located in the rear of the vehicle, behind a quarter trim panel in the trunk or hatch area.. This is the slave module in the communication link. Physical access is needed to test its connectors (R221 or R80) or to replace it.
• BIU Connector i171, Pin 11 — At the Body Integrated Unit under the driver's dash.. This is the specific pin for the UART communication signal wire to the keyless entry module. It's a primary test point for checking harness continuity.
• Keyless Module Connector R221 (for models with TPMS) — At the Keyless Entry Control Module in the rear of the vehicle.. Pin 4 is for power (≥10V), Pin 5 is for ground (≤10Ω), and Pin 11 is the UART signal. These are the essential test points defined in the TSB.
• Keyless Module Connector R80 (for models without TPMS) — At the Keyless Entry Control Module in the rear of the vehicle.. Pin 7 is for ground and Pin 3 is for the UART signal. These are the test points for non-TPMS vehicles.

OEM Part Supersession History

• 88035-FJ020 → 88035-FJ021 — Standard part revision or update by the manufacturer.
  Heads up: The new part number should be a direct replacement for the old one, but always verify fitment with a VIN.

Model Year Variations Within This Range

• 2015-2016: The Impreza received a mid-generation facelift for the 2015 model year. Changes included a revised front bumper and grille, additional sound deadening, thicker window glass, a standard backup camera, and new infotainment systems. While these changes were significant for comfort and aesthetics, the diagnostic procedure for the B1500 keyless communication fault remained the same as outlined in TSB 07-83-14, which covers the 2014-2015 model years.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Excessive Engine Oil Consumption 🔴 High — Widespread on 2012-2015 models with the 2.0L FB20 engine. Caused by faulty oil control piston rings. Consumption rates could exceed 1 quart per 1,200 miles. (Ref: TSB 02-157-14R. Subaru addressed this via a class-action lawsuit settlement, extending warranties and replacing short blocks on affected vehicles that failed an oil consumption test.)
• CVT (TR580) Transmission Problems 🔴 High — Common issues include failing torque converter lock-up solenoids or valve body failure, often occurring between 80,000 and 120,000 miles. Symptoms include shuddering, stalling when stopping, or hesitation. (Ref: Subaru extended the CVT warranty to 10 years/100,000 miles for many models. TSBs like 16-90-13R address specific torque converter issues.)
• Prematurely Worn Suspension Bushings and Components 🟠 Medium — Owners report replacing front lower control arm bushings, sway bar links, and wheel bearings sooner than expected, sometimes as early as 60,000 miles (100,000 km). Symptoms include clunking or popping noises over bumps.
• Faulty Brake Light Switch 🔴 High — Widespread enough to trigger a recall. The switch malfunction could prevent brake lights from illuminating, prevent the vehicle from starting, or prevent the transmission from being shifted out of Park. (Ref: NHTSA Recall 18V772000)
• Fracturing Engine Valve Springs 🔴 High — A recall was issued for this potential failure, which could lead to engine malfunction or stalling while driving. (Ref: NHTSA Recall 16V738000)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used part is a smart, cost-effective choice for the Keyless Entry Control Module, as it is not VIN-locked. A used Body Integrated Unit (BIU) is only a viable option if you have a confirmed plan to use a mail-in cloning service to transfer your original immobilizer data to the donor unit.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For the Keyless Entry Module, ensure the donor vehicle shows no signs of water leaks in the trunk or hatch area.
• For the BIU, you must match the OEM part number from your original module EXACTLY. Part numbers vary by trim and options.
• Inspect any used module's case for physical damage and check all connector pins for corrosion, water damage, or being bent.

OEM-only on this vehicle (don't cheap out):

• Body Integrated Unit (BIU) - Due to the mandatory immobilizer programming, a new OEM part programmed by a dealer or a cloned used OEM part are the only reliable options.

Brands owners have reported issues with on this vehicle:

• No-name or unbranded electronic modules from online marketplaces. For critical components like the BIU and keyless module, stick with OEM or a tested used OEM part.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• B1500 — The primary companion code for this platform; TSB 07-83-14 identifies B1500 as the keyless entry communication fault code for the Impreza, while U1500 is used for the WRX/STI.
• B1500 (FUEL VARIANT) — Identified in TSB 09-63-16 as a code for fuel level sensor faults, which can lead to misdiagnosis of the keyless entry system.

Frequently Asked Questions