P04E2: Crankcase Ventilation Hose Connection Sensor Circuit Low

What does P04E2 mean?

The crankcase ventilation (PCV) system routes blow-by gas from the crankcase into the intake; CARB requires a disconnection between crankcase and intake to be detected. GM's 2.0-litre LSY has a pressure sensor in the PCV hose: with the hose connected it must see a pressure drop that grows with air flow, plus pressure pulses from the pistons. Ford reports the same sensor type as crankcase pressure sensor A (P051A ff). P04E2 means the sensor signal is too low: GM's LSY sets it at 4.3 % of 5 V or less (about 0.22 V) in 1280 of 1600 samples, MIL after two trips. With this ratiometric sensor an open signal line also reads low, as does a missing 5 V reference. The disconnection check P04DB is then suspended.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Disconnection check P04DB does not run
• Usually no change in driving

Common causes

• High Signal line open or shorted to ground
• Medium 5 V reference open or shorted (often shared with other sensors)
• Medium Connector not latched or corroded
• Medium Sensor faulty

Likelihood is a general estimate across vehicles; your make and model may differ.