P0B06 — Auxiliary Transmission Fluid Pump Motor Phase W Current #

The description of this Diagnostic Trouble Code (DTC) may vary depending on your vehicle’s manufacturer. Always refer to your OEM (Original Equipment Manufacturer) service information for the most accurate definition.

Known variations of the code description:

• P0B06 – “Auxiliary Transmission Fluid Pump Motor Phase W Current” (Generic/OEM)
• P0B06 – “Auxiliary ATF Pump Phase W Circuit” (Toyota/Lexus)
• P0B06 – “Hybrid Transmission Pump Phase W Current Abnormality” (Honda/Acura)
• P0B06 – “Auxiliary Motor Phase W Current Out of Range” (GM/Chevrolet)

Summary of DTC P0B06 #

P0B06 is a generic powertrain code that indicates a problem detected in the current measurement of the Phase W circuit of the auxiliary transmission fluid pump motor. This pump is typically found in hybrid or electrified automatic transmissions, where it maintains fluid pressure when the main engine is off or during start-stop operation. The code is set when the transmission control module (TCM) detects a current reading in the Phase W portion of the three-phase auxiliary pump motor that falls outside of expected limits. This can affect transmission lubrication and shifting, especially at low speeds or during electric-only operation.

Driving with this code could potentially lead to transmission performance concerns and, over time, cause damage if not addressed. Prompt diagnosis and repair are advised to avoid costly repairs down the road.

Common Symptoms for DTC P0B06 #

Most drivers may not notice immediate severe symptoms when this code is triggered, but subtle changes can develop. The auxiliary transmission fluid pump’s role is crucial for proper lubrication and hydraulic pressure, especially in hybrid vehicles. Here are some common symptoms you might encounter:

• Warning lights: Check Engine or Hybrid System warning lamp illuminated
• Transmission performance issues: Delayed or harsh shifting, especially at low speeds
• Reduced hybrid/electric drive capability: Loss of EV mode or reduced electric assist
• Unusual noises: Whining or buzzing from the transmission area
• In some cases: Transmission overheating warning or limp-home mode activation

Likely Causes of DTC P0B06 (In Order of Frequency) #

Several issues can trigger the P0B06 code. The TCM is monitoring electrical current in the “W” phase (one leg of a 3-phase motor) and expects it to match a set pattern. When it doesn’t, the cause is usually electrical or mechanical in nature. Here are the most common culprits, listed by likelihood:

1. Faulty auxiliary transmission fluid pump motor (internal short/open in Phase W winding)
2. Damaged wiring or poor connection in the Phase W circuit (corrosion, chafing, loose pins)
3. Faulty transmission control module (TCM) (rare, but possible)
4. Blown fuse or relay for the auxiliary pump circuit
5. Contaminated transmission fluid causing pump resistance (less common)

Step-by-Step Diagnostic Procedure for P0B06 #

To accurately diagnose the P0B06 trouble code, methodical and safe steps should be followed. Always start with the basics before replacing expensive components. Here’s a proven approach:

• 1. Confirm the code: Use a scan tool to verify P0B06 is present and record any related freeze-frame data.
• 2. Visual inspection: Inspect the auxiliary pump’s wiring harness and connectors for visible damage, corrosion, or loose connections, especially in the Phase W circuit.
• 3. Check fuses and relays: Locate the auxiliary pump’s power supply and verify all fuses and relays are intact and functioning.
• 4. Measure resistance: With the power off, use a multimeter to check the resistance of the Phase W winding at the pump motor. Compare values to OEM specs.
• 5. Check for shorts/opens: Test for continuity and shorts to ground in the Phase W circuit using wiring diagrams.
• 6. Command the pump ON (if possible): With a scan tool, attempt to activate the auxiliary pump and monitor current draw and operation.
• 7. Test the transmission control module (TCM): If all wiring and pump tests pass, consider TCM diagnosis/replacement as a last resort.

Possible Repairs for DTC P0B06 #

Repair options depend on the underlying cause discovered during diagnosis. It’s vital to fix the root problem, not just clear the code. Here are common repairs linked to the most frequent causes:

• Repair or replace damaged wiring/connectors in the Phase W circuit
• Replace faulty auxiliary transmission fluid pump motor (if windings are shorted/open)
• Replace blown fuse or faulty relay for the pump circuit
• Flush or replace contaminated transmission fluid (if fluid is the culprit)
• Replace the transmission control module (TCM) (only after all other options tested)

Is It Safe to Drive with Code P0B06? #

Driving with P0B06 is generally not recommended, especially for extended periods. While the vehicle may operate normally at first, the auxiliary transmission fluid pump is essential for proper lubrication and hydraulic pressure, particularly during hybrid operation or low engine speeds. Ignoring this issue can lead to transmission overheating, erratic shifting, or even long-term damage to internal components. If the code appears, have your vehicle inspected and repaired as soon as possible.

Vehicles Most Commonly Affected by P0B06 #

This code is most often seen in modern hybrid and some plug-in hybrid models, as well as newer vehicles with advanced automatic transmissions that use auxiliary electric fluid pumps. While almost any vehicle with this technology can set this code, these makes and models are frequently affected:

• Toyota Prius, Camry Hybrid, RAV4 Hybrid
• Lexus ES/GS/LS Hybrid models
• Honda Accord Hybrid, Clarity, Insight
• Chevrolet Volt, Malibu Hybrid
• Ford Fusion Hybrid, Escape Hybrid
• Hyundai Ioniq/Kona Hybrid
• Kia Niro Hybrid

Common Mistakes & Best Practices for P0B06 #

Misdiagnosing P0B06 can lead to unnecessary part replacements or recurring issues. Here’s how to avoid common pitfalls and ensure a lasting repair:

• Don’t replace the pump motor without checking the wiring first. Many issues are caused by damaged connectors or corroded terminals.
• Always use OEM wiring diagrams for accurate circuit identification.
• Don’t ignore fuse/relay checks—a blown fuse can mimic a failed motor.
• Resist the urge to clear the code without addressing the cause. It will likely return quickly and may mask a developing problem.
• After repairs, always verify with a scan tool that the code is gone and the system operates as expected.

Express FAQ for DTC P0B06 #

Curious about this code? Here are quick answers to the most common questions:

• Q: Can I fix P0B06 myself?
  A: If you’re comfortable with basic electrical testing and have access to wiring diagrams, you may be able to inspect connectors and fuses. More involved repairs—like motor or TCM replacement—are best left to a professional.
• Q: Will clearing the code turn off my warning light?
  A: Temporarily, yes. But unless the root cause is fixed, the code and warning light will return—sometimes immediately.
• Q: Is this code covered under warranty?
  A: Many hybrid and transmission components have extended warranties, especially for emissions-related parts. Check with your dealer or OEM for details.