P0C27 — Auxiliary Transmission Fluid Pump Motor Current Low #

Note: The label for DTC P0C27 may vary depending on the vehicle manufacturer (OEM). Always refer to your service manual for the exact description relevant to your make and model.

• P0C27: Auxiliary Transmission Fluid Pump Motor Current Low (Generic / Toyota / Lexus / Ford / GM)
• P0C27: Low Current Detected in Auxiliary Transmission Oil Pump Motor Circuit (Nissan)
• P0C27: Auxiliary ATF Pump Motor Low Current (Hyundai / Kia)

Summary of DTC P0C27 #

The P0C27 diagnostic trouble code (DTC) indicates that the Engine Control Module (ECM) or Transmission Control Module (TCM) has detected an abnormally low electrical current being drawn by the auxiliary transmission fluid pump motor. This auxiliary pump supports fluid flow in the automatic transmission, especially in hybrid or start-stop systems where the main pump might be inactive. When current is lower than expected, it can point to a wiring issue, a failing pump motor, or an ECM/TCM malfunction. If this code appears, transmission performance and cooling may be compromised, potentially leading to further drivability issues if not addressed.

Frequent Symptoms for Code P0C27 #

Drivers may notice a range of symptoms when the P0C27 code is present. Some vehicles may show only a warning light, while others can experience more severe drivability problems. Common symptoms include:

• Illuminated “Check Engine” or “Transmission” warning light
• Erratic or harsh gear shifts
• Delayed engagement when shifting from Park to Drive or Reverse
• Reduced fuel efficiency, especially in hybrids or start-stop vehicles
• Transmission entering limp or fail-safe mode
• Overheating transmission, particularly during stop-and-go traffic

Probable Causes for P0C27 (Ranked by Frequency) #

Several potential issues can trigger the P0C27 code, but some are more common than others. Understanding these helps prioritize diagnosis and repair:

1. Faulty auxiliary transmission fluid pump motor — The most frequent cause, especially in high-mileage vehicles or those with extended stop/start operation.
2. Damaged or corroded wiring/connectors — Broken, shorted, or corroded circuits to the pump can reduce current draw.
3. Blown fuse or faulty relay — A failed fuse or relay in the auxiliary pump circuit can cause insufficient power delivery.
4. PCM/TCM malfunction — Rare, but possible if control logic or internal drivers fail.
5. Low transmission fluid level or contamination — Uncommon, but can cause the pump to work improperly or overheat.

Step-by-Step Diagnostic for Code P0C27 #

A systematic diagnostic approach ensures you don’t overlook simple issues. Always follow OEM-specific procedures, but here’s a general outline:

• 1. Verify the code: Use a scan tool to confirm P0C27 is present and check for related DTCs.
• 2. Inspect wiring and connectors: Look for broken, frayed, or corroded wires and loose connectors at the pump and control module.
• 3. Check fuse and relay: Locate and test the fuse and relay associated with the auxiliary pump circuit.
• 4. Test the pump motor: Using a multimeter, measure the resistance and current draw of the pump motor. Compare values to OEM specs.
• 5. Inspect the fluid: Check transmission fluid level and quality. Refill or replace as needed.
• 6. Assess PCM/TCM: If all else checks out, consult OEM flowcharts for control module testing or reprogramming.

Possible Repairs for P0C27 #

Once the root cause is identified, repairs can be targeted and efficient. Address the most likely issues first to restore normal transmission operation:

• Replace auxiliary transmission fluid pump motor if it fails resistance or current draw tests.
• Repair or replace damaged wiring/connectors in the pump circuit.
• Replace blown fuse or faulty relay supplying power to the pump.
• Top up or flush transmission fluid if level is low or fluid is contaminated.
• Update or reprogram PCM/TCM per OEM bulletins, or replace if confirmed faulty.

Is It Safe to Drive with Code P0C27? #

Driving is not recommended with code P0C27 active. The auxiliary transmission fluid pump plays a critical role in maintaining proper lubrication and cooling, especially in hybrids and vehicles with start-stop technology. Continued driving may lead to harsh shifting, overheating, or failure to engage gears—potentially causing severe transmission damage. Prompt diagnosis and repair are advised to prevent costly repairs and ensure vehicle safety.

Vehicles Most Commonly Affected by P0C27 #

While the P0C27 code can appear in a variety of makes and models, it is most commonly reported in vehicles using hybrid or stop/start systems, including:

• Toyota and Lexus hybrids (Prius, Camry Hybrid, RXh, etc.)
• Ford hybrids (Fusion Hybrid, C-Max, Escape Hybrid)
• General Motors hybrids (Chevrolet Volt, Malibu Hybrid)
• Nissan Altima Hybrid
• Hyundai/Kia hybrids (Sonata Hybrid, Ioniq, Niro)

Common Mistakes & Best Practices for P0C27 #

Even experienced technicians can miss simple issues or misinterpret test results when diagnosing P0C27. To avoid wasted time and misdiagnosis, keep these points in mind:

• Neglecting to check connectors for corrosion or loose pins
• Overlooking related codes that might point to upstream issues
• Assuming the pump is faulty without testing power and ground first
• Not consulting OEM service information for specific test procedures
• Failing to confirm repairs by clearing codes and performing road tests

Express FAQ: P0C27 #

Q: Can a weak 12V battery cause the P0C27 code?
A: Yes, especially in hybrids, a weak or failing 12V battery can reduce voltage to the pump circuit, triggering low current codes like P0C27. Always check battery health as part of your diagnosis.

Q: Does replacing the auxiliary pump require transmission removal?
A: Not usually. In most cases, the auxiliary pump is mounted externally or accessible from underneath the vehicle, but always refer to OEM repair instructions for your specific model.