P04E2 code meaning
Crankcase Ventilation Hose Connection Sensor Circuit Low
Powertrain system Generic code P04xx codes Check engine light
What P04E2 means
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.
P04E2 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P04E2
- Check engine light on
- Disconnection check P04DB does not run
- Usually no change in driving
Common causes of P04E2
- Most likelySignal line open or shorted to ground
- Possible5 V reference open or shorted (often shared with other sensors)
- PossibleConnector not latched or corroded
- PossibleSensor faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Crankcase ventilation hose sensorSensor wiringEngine control module
What each part of P04E2 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| E2 | The exact fault in that area. |
What to do next
- Note P04E2 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P04E2
What does P04E2 mean?
P04E2 means "Crankcase Ventilation Hose Connection Sensor Circuit Low". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P04E2?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P04E2 fail an emissions test?
Yes, it can. P04E2 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P04E2 to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P04E2 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.