What it means
Same as P24B8 with the signal voltage above the plausible range. The evaporative system captures fuel vapor from the tank and purges it into intake; leaks or stuck purge valves leak hydrocarbons and cause emissions failures.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The leak detection pump pressure sensor reports pressure in the EVAP system so the control module can check for leaks. P24BB sets when its signal is higher than the range the module considers plausible, which can prevent a reliable leak test.
Common causes
Most likely first.
- Signal shorted to supply
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light on
- Possible smell of fuel near tank or engine bay
- Failed emissions inspection
- Loose-cap warning may appear
How to diagnose it
- Save freeze-frame data and compare the pressure sensor reading with other EVAP data to see whether it is implausibly high or fixed.
- With the vehicle off, inspect the pressure sensor connector and harness for corrosion, damaged insulation, pinched wires, or contact with a power source.
- Check the connector pins for corrosion, looseness, or poor contact that could raise resistance in the signal path.
- Use the wiring diagram to test the sensor signal, supply, and ground circuits for a short to supply, following the manufacturer's procedure.
- If the wiring checks pass, test the pressure sensor against the manufacturer's specification and replace it only if it fails.
Common fixes
- Repair a signal wire shorted to a power feed.
- Clean or repair corroded or loose connector terminals.
- Replace damaged wiring or secure a harness pinched against a power source.
- Replace the EVAP pressure sensor if it fails testing.
Can I keep driving?
Usually the vehicle remains driveable, but the EVAP leak test may not work and the vehicle may fail an emissions inspection. Avoid ignoring a fuel smell; have the vehicle checked promptly if the smell is strong or persistent.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.