What it means
The control module detects a low signal in the EVAP leak detection pump heater control circuit. This code concerns that heater circuit, not a lambda sensor heater.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The EVAP leak detection pump heater warms the pump or related sensing components when needed. The control module monitors the heater control line and sets P240B when its signal is lower than expected, which can happen if the line is shorted to ground. This is the EVAP pump heater circuit, not a lambda-sensor heater circuit.
Common causes
Most likely first.
- Control line shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light on
How to diagnose it
- Review freeze-frame and heater-circuit live data, if available, to confirm that the low signal occurs when the heater is commanded.
- Inspect the heater connector and harness for corrosion, chafing, or insulation worn through to ground.
- Check connector pins for corrosion or poor contact that could distort the control-line signal.
- With the circuit isolated as specified by the manufacturer, test the control line for a short to ground and check its continuity.
- If the wiring is sound, test the pump-heater load and control output against the manufacturer's specification.
Common fixes
- Clean and secure corroded or loose heater-circuit connections.
- Repair insulation where the control line is chafed or shorted to ground.
- Replace a failed pump-heater element or assembly if it does not meet specification.
- Repair a confirmed control-output fault in the relevant module.
Can I keep driving?
The code generally affects EVAP monitoring rather than engine power, so short-term driving is usually possible if the vehicle runs normally and there is no fuel odor or leak. The check-engine light may remain on and emissions checks may not complete until the circuit is repaired.
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.