What it means
The control module detects an implausible correlation among throttle position, manifold pressure, and/or mass airflow readings.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The control module compares throttle-position data with manifold absolute pressure and mass-airflow readings to check whether the engine's measured airflow matches throttle opening and load. P0068 sets when those readings do not correlate plausibly, which can be caused by unmetered air, a sticking throttle body, or a drifting airflow sensor.
Common causes
Most likely first.
- Large unmetered vacuum leak
- Throttle body dirty or sticking
- MAF sensor drift
Symptoms
- Check engine light on
- Power loss, hesitation under acceleration
- Rough or unstable idle
- Increased fuel consumption
- Possible difficulty starting
How to diagnose it
- Record freeze-frame data and compare live throttle position, MAP, and MAF readings at idle and during a gentle increase in engine speed.
- Inspect the intake ducting, vacuum hoses, and manifold connections for a large leak that could admit air the MAF does not measure.
- Check the throttle body for dirt or sticking and confirm the throttle-position reading changes smoothly.
- Inspect the MAF and MAP sensor connectors and wiring, then check sensor readings for plausibility using the manufacturer's specification.
- If no leak or wiring fault is found, test the throttle body, MAF, and MAP sensors using the manufacturer's diagnostic procedure.
Common fixes
- Repair a split intake hose, disconnected vacuum line, or other confirmed air leak.
- Clean the throttle body using a method suitable for the vehicle and verify that it moves freely.
- Repair a loose or damaged MAF, MAP, or throttle-position sensor connector or wire.
- Replace a MAF, MAP, or throttle body component only if testing confirms it is faulty.
Can I keep driving?
If the engine hesitates, idles erratically, or loses power, avoid busy traffic and hard acceleration because response may be unpredictable. A substantial air leak or incorrect airflow reading can make starting and running worse and increase fuel use.
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.