P0C24 — Auxiliary Transmission Fluid Pump Control Module Circuit Low #

Note: The exact wording of this DTC may vary depending on the vehicle manufacturer.

• P0C24: Auxiliary Transmission Fluid Pump Control Module Circuit Low (Generic/SAE)
• P0C24: Auxiliary Transmission Fluid Pump Control Circuit Low (Toyota/Lexus)
• P0C24: Secondary Transmission Pump Module Circuit Low (Ford)
• P0C24: Aux Trans Fluid Pump Control Module Low (Hyundai/Kia)

Summary of DTC P0C24 #

DTC P0C24 signals that the Auxiliary Transmission Fluid Pump Control Module is reporting a low voltage or current in its control circuit. This auxiliary pump is an electric unit that helps maintain hydraulic pressure in the transmission, especially in hybrid or start-stop vehicles when the main engine-driven pump is off. The Powertrain Control Module (PCM) or Transmission Control Module (TCM) monitors this circuit for correct operation. When the circuit voltage or current drops below the threshold set by the OEM, the code is triggered. Left unchecked, this issue can affect gear shifting and overall transmission reliability.

Frequent Symptoms for Code P0C24 #

When P0C24 is active, drivers may notice several warning signs. These symptoms can range from minor inconveniences to more serious drivability issues, depending on how reliant the transmission system is on the auxiliary pump.

• Transmission warning light or check engine light illuminated
• Harsh or delayed gear shifts
• Transmission stuck in limp mode (reduced power/protection mode)
• Unusual noises from the transmission area, especially at low speeds or idle
• Inoperative start-stop function (in hybrid or stop/start cars)
• Erratic or unpredictable gear changes

Likely Causes for Code P0C24 #

The most common reasons for a P0C24 code relate to electrical or control faults within the auxiliary pump circuit. These causes, listed from most to least frequent, should guide your diagnostic approach.

1. Faulty auxiliary transmission fluid pump (internal electrical failure or short)
2. Damaged wiring or poor connections in the pump control circuit
3. Failed relay or fuse supplying the auxiliary pump
4. Faulty control module (PCM/TCM or dedicated pump control unit)
5. Corroded, loose, or contaminated connectors at the pump or module
6. Low system voltage or weak battery causing circuit underperformance

Step-by-Step Diagnosis for P0C24 #

A systematic approach is vital for correctly diagnosing the P0C24 code. Follow these steps to pinpoint the root cause, using appropriate tools such as a scan tool, multimeter, and wiring diagrams.

1. Verify the code and check for other related DTCs using a professional scan tool.
2. Inspect the auxiliary pump’s wiring and connectors for obvious damage, corrosion, or looseness.
3. Test the pump’s power and ground circuits using a multimeter — look for proper voltage and continuity.
4. Check all related fuses and relays in the auxiliary pump circuit.
5. Command the pump ON and OFF using scan tool bi-directional controls (if available) to verify operation.
6. Measure circuit voltage and current draw at the pump during operation; compare to OEM specs.
7. Inspect for battery or charging system issues that could cause low voltage conditions.
8. If all wiring and power tests pass, consider internal pump failure or module issue — consult manufacturer flowcharts.

Possible Repairs for Code P0C24 #

Once the cause is identified, repairs should directly address the issue found during diagnosis. Here are the most common solutions:

• Replace the auxiliary transmission fluid pump if it fails electrical or operational tests.
• Repair or replace damaged wiring/connectors in the pump control circuit.
• Replace a blown fuse or faulty relay feeding the pump circuit.
• Clean or secure corroded connectors at the pump or module.
• Replace the control module if it’s determined to be faulty (PCM/TCM or pump controller).
• Address battery or charging system problems causing low voltage.

Can You Drive With Code P0C24? #

It’s generally not recommended to drive for extended periods with P0C24 active. While the car may remain drivable in limp or reduced power mode, transmission performance can be severely affected. Lack of proper fluid pressure may cause erratic shifting, slipping, or even transmission damage over time. If you must drive, do so cautiously and only as far as necessary for diagnosis or repair.

Vehicles Most Commonly Affected by P0C24 #

P0C24 is most frequently encountered in hybrid models or vehicles with start-stop technology, since these rely on electric auxiliary pumps to maintain hydraulic pressure. However, some conventional automatics with advanced transmission technology may also use auxiliary pumps.

• Toyota Prius, Camry Hybrid, RAV4 Hybrid
• Lexus ES/RX/GS Hybrid series
• Ford Fusion Hybrid, C-MAX Hybrid, Escape Hybrid
• Hyundai Sonata Hybrid, Ioniq
• Kia Niro, Optima Hybrid
• Other select Nissan, Honda, GM, and European hybrid models

Common Mistakes & Best Practices with P0C24 #

Misdiagnosis or skipping steps can lead to unnecessary part replacement. Avoid these pitfalls by following proven practices.

• Assuming the pump is bad without testing — always verify wiring, power, and grounds first.
• Overlooking corroded or loose connectors — these are frequent culprits, especially in wet or salty climates.
• Neglecting battery and charging system checks — low voltage can mimic control circuit faults.
• Not checking for related codes — other DTCs may point to underlying causes.
• Using the wrong wiring diagram — always match diagrams to the exact year, make, and model.

Quick FAQ on P0C24 #

Here are quick answers to the top questions about this code:

• Q: Is P0C24 a transmission failure?
  A: Not directly, but it signals a problem in the system that maintains transmission pressure. Ignoring it can lead to serious transmission issues.
• Q: Can I clear the code and keep driving?
  A: Clearing the code without fixing the root cause may make the warning light go out temporarily, but the problem will return—and could get worse if not addressed.
• Q: Does P0C24 mean I need a new transmission?
  A: Not usually. Most cases involve electrical faults or a failed pump, not complete transmission failure.