Crankcase ventilation hose connection sensor internally shorted to ground; Damaged or corroded electrical connector at the sensor; Chafed or broken signal wire shorting to chassis ground; Hose connection sensor improperly installed or loose after recent service; Engine control module internal fault on the sensor input circuit (rare)

DTC codes / P04xx · Auxiliary emission controls / P04E2

P04E2Crankcase Ventilation Hose Connection Sensor Circuit Low

Q: What does code P04E2 mean?

Crankcase Ventilation Hose Connection Sensor Circuit Low. P04E2 indicates that the engine control module has detected a low-voltage condition on the circuit for the crankcase ventilation hose connection sensor, which is a component used to verify that the crankcase ventilation hose is properly attached. The sensor circuit is expected to carry a specific voltage, and a low reading means the signal wire is likely shorted to ground, the sensor has failed, or the connector is damaged.

P04E2 indicates that the engine control module has detected a low-voltage condition on the circuit for the crankcase ventilation hose connection sensor, which is a component used to verify that the crankcase ventilation hose is properly attached. The sensor circuit is expected to carry a specific voltage, and a low reading means the signal wire is likely shorted to ground, the sensor has failed, or the connector is damaged.

SystemPowertrain

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Rough idle or slight hesitation if the hose is actually disconnected and causing a vacuum leak
Increased oil consumption or oil seepage from seals due to crankcase pressure issues
A faint hissing or whistling noise from the engine bay if the hose is loose or cracked
Possible lean fuel trim codes or misfire codes stored alongside P04E2

Common causes, most likely first

Crankcase ventilation hose connection sensor internally shorted to ground
Damaged or corroded electrical connector at the sensor
Chafed or broken signal wire shorting to chassis ground
Hose connection sensor improperly installed or loose after recent service
Engine control module internal fault on the sensor input circuit (rare)

How to diagnose and fix it

Inspect the crankcase ventilation hose and sensor connector for physical damage, corrosion, or looseness
Disconnect the sensor and check for a short to ground on the signal wire using a digital multimeter
Verify reference voltage and ground at the sensor connector with the key on and engine off
Test the sensor resistance or output signal according to the manufacturer's specification
Repair any damaged wiring or replace the connector terminals as needed
Replace the crankcase ventilation hose connection sensor if it fails electrical testing
Clear the diagnostic trouble codes and verify the repair with a test drive and live data review

Don't overlook the hose itself

A disconnected or cracked crankcase ventilation hose can set P04E2 even when the sensor and wiring are perfectly functional, so always inspect the hose routing and fitment first.
Technicians often replace the sensor without checking for a shorted signal wire, which leads to a repeat code and wasted parts.
The sensor circuit is sensitive to water intrusion at the connector, especially on vehicles that see road spray or frequent engine washing.
P04E2 can be stored intermittently by a loose connector that only loses contact during engine vibration, so wiggle-test the harness while monitoring live data.
This code does not always mean the sensor has failed; a low reference voltage from a shared circuit can trigger it, so check for other codes on the same five-volt reference.

Can I keep driving with P04E2?

The vehicle is generally safe to drive with P04E2 because it does not affect engine operation directly, but you should avoid ignoring it for long periods since a disconnected hose can cause oil leaks or unmetered air entering the engine. Have the circuit inspected at your next service appointment.

Tools that help

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