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DTC codes / P2Cxx · Hybrid propulsion / P2C24

P2C24Exhaust Heat Exchanger Exhaust Bypass Valve A Position Sensor Circuit Low

P2C24 indicates that the powertrain control module has detected a low voltage signal from the exhaust bypass valve position sensor on the exhaust heat exchanger. This sensor monitors the valve that routes exhaust gas either through or around the heat exchanger, and a low signal means the circuit is grounded, shorted, or the sensor is failing.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms.
  • Reduced fuel economy due to the system defaulting to a less efficient operating mode.
  • Inability to enter or maintain engine warm-up mode, leading to longer warm-up times.
  • Possible rough running or hesitation during cold starts if the bypass valve remains in the wrong position.
  • In some vehicles, a message indicating that the exhaust heat recovery system is unavailable.
  • No perceptible change in driveability in many cases, as the fault may only affect emissions and efficiency.

Common causes, most likely first

  1. A short to ground in the signal wire between the position sensor and the PCM.
  2. A faulty exhaust bypass valve position sensor, often due to internal wear or contamination.
  3. Corroded, loose, or damaged electrical connector at the sensor or PCM.
  4. A defective bypass valve actuator that fails to move the valve, causing the sensor to read out of range.
  5. Mechanical binding or obstruction of the bypass valve, preventing it from reaching the expected position.
  6. A failed PCM driver circuit for the sensor reference or signal return, though this is less common.
  7. Exhaust leaks or extreme heat damage affecting the sensor wiring or sensor itself.

How to diagnose and fix it

  1. Connect a scan tool and verify P2C24 is active, then check for any related codes in the exhaust heat exchanger system.
  2. Inspect the sensor wiring and connector for signs of chafing, corrosion, or loose pins, and repair as needed.
  3. Measure the sensor signal voltage with a multimeter while monitoring the scan tool data to confirm a low reading.
  4. Disconnect the sensor and check the reference voltage and ground circuits to rule out wiring or PCM issues.
  5. Test the bypass valve actuator for proper movement and compare the sensor reading through its full range.
  6. Replace the exhaust bypass valve position sensor if the circuit tests good but the signal remains low.
  7. Clear codes and perform a road test to confirm the repair and ensure the monitor runs to completion.

Exhaust Bypass Sensor Diagnostics Beyond the Code

  • A low signal code often results from a short to ground in the sensor wiring rather than a failed sensor, so always check the harness near hot exhaust components first.
  • The bypass valve may be stuck due to carbon buildup, causing the sensor to read low even when the electrical circuit is intact.
  • Some vehicles use the same sensor for both heat exchanger bypass and other exhaust flow functions, so a misdiagnosis can lead to replacing the wrong component.
  • The PCM may set this code only after a specific drive cycle, so a simple key-on test might not reveal the fault.
  • Extreme heat cycling can cause the sensor's internal resistance to change, producing a low signal without any visible wiring damage.

Can I keep driving with P2C24?

You can generally continue driving with this code, but avoid prolonged idling and heavy loads until it is repaired, as the system may not regulate exhaust temperature properly. If the check engine light begins flashing or you notice performance issues, stop driving and seek service.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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