P0C21 Code - Auxiliary Transmission Fluid Pump Phase U-V-W Circuit Low
Quick Answer
The P0C21 diagnostic trouble code (DTC) indicates a problem with the Auxiliary Transmission Fluid Pump Phase U-V-W Circuit being detected as low. Common causes include Faulty auxiliary transmission fluid pump: The pump may be malfunctioning, causing low voltage in the U-V-W circuit, Wiring issues: Damaged or corroded wiring connections can disrupt the flow of electricity to the auxiliary pump, PCM malfunction: A problem with the powertrain control module can lead to incorrect voltage readings in the U-V-W circuit. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- P0C21 indicates Auxiliary Transmission Fluid Pump Phase U-V-W Circuit Low.
- Common causes
- Common causes include Faulty auxiliary transmission fluid pump: The pump may be malfunctioning, causing low voltage in the U-V-W circuit, Wiring issues: Damaged or corroded wiring connections can disrupt the flow of electricity to the auxiliary pump, PCM malfunction: A problem with the powertrain control module can lead to incorrect voltage readings in the U-V-W circuit.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
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Code P0C21 Description
The P0C21 diagnostic trouble code (DTC) indicates a problem with the Auxiliary Transmission Fluid Pump Phase U-V-W Circuit being detected as low. This code is typically found in hybrid vehicles with electrically driven auxiliary transmission fluid pumps. The auxiliary pump is responsible for maintaining proper fluid pressure in the transmission system, ensuring smooth gear shifts and optimal performance.
Common Causes of P0C21
- Faulty auxiliary transmission fluid pump: The pump may be malfunctioning, causing low voltage in the U-V-W circuit.
- Wiring issues: Damaged or corroded wiring connections can disrupt the flow of electricity to the auxiliary pump.
- PCM malfunction: A problem with the powertrain control module can lead to incorrect voltage readings in the U-V-W circuit.
- Low transmission fluid levels: Insufficient fluid in the transmission system can affect the performance of the auxiliary pump.
Symptoms of P0C21
- Erratic shifting: The vehicle may experience rough or delayed gear shifts.
- Transmission slippage: The transmission may slip out of gear or struggle to engage properly.
- Decreased fuel efficiency: The vehicle may consume more fuel than usual due to inefficient transmission operation.
- Illuminated warning light: The check engine light may come on to indicate a problem with the transmission system.
How to Fix P0C21
- Diagnose the issue: Use a diagnostic scanner to retrieve the DTC and pinpoint the exact cause of the problem.
- Inspect the auxiliary pump: Check the condition of the auxiliary transmission fluid pump and its connections for any signs of damage.
- Test the wiring: Verify the integrity of the wiring harness and connectors in the U-V-W circuit to ensure proper electrical flow.
- Replace faulty components: Replace the auxiliary pump, wiring harness, or PCM as needed to address the low voltage issue.
- Clear the DTC: After completing the repairs, clear the DTC from the PCM memory to reset the system and monitor for any recurring issues.
Cost to Fix P0C21
The cost of repairing a P0C21 code can vary depending on the specific cause of the issue and the labor rates in your area. On average, you can expect to pay between $200 and $500 for parts and labor. Keep in mind that diagnostic time and labor rates at auto repair shops can fluctuate, so it's recommended to obtain quotes from multiple sources to ensure a fair price. Remember that prompt attention to this issue can prevent more extensive and costly transmission repairs down the line.
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