P0068

What it means

P0068 means the engine control unit has found that the air flow or manifold pressure reading (MAP/MAF) does not agree with the throttle position it expects. The ECU compares the measured air load with the throttle angle and, when the two do not correlate over a set period, it logs the fault. It points to a sensor, air leak or throttle problem rather than naming one failed part.

Symptoms

• Malfunction indicator lamp on
• Poor or hesitant acceleration
• Rough or unstable idle
• Engine stalling or hunting at idle
• Reduced power or limp mode
• Poor fuel economy

Possible causes

• Unmetered air leak after the air flow meter, such as a split intake hose, loose clip or leaking intake manifold gasketlikely
• Dirty or faulty mass air flow sensor giving an inaccurate readinglikely
• Faulty or contaminated manifold absolute pressure sensor, or a blocked or cracked vacuum line to itpossible
• Dirty throttle body or throttle plate, or a faulty throttle position sensor or throttle actuatorpossible
• Damaged wiring, poor connector contact or corrosion in the sensor or throttle circuitspossible
• Restricted air filter or blocked intake, or an exhaust restriction affecting manifold pressurerare
• Faulty ECU or outdated software calibration (model dependent)rare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting load, throttle angle, engine speed and temperature when the fault set.
2. Inspect the air filter, intake pipework, clips and breather hoses for splits, loose joints or disconnections.
3. Check the wiring and connectors for the MAF, MAP and throttle position sensors for damage, corrosion, chafing and poor pin tension.
4. Look at live data at idle and with the throttle held steady: compare MAF, MAP and throttle angle against the expected values for the engine and check they change smoothly.
5. Check the throttle body for carbon build-up and confirm the throttle moves smoothly through its full range without sticking.
6. Check for intake leaks with a smoke test and inspect vacuum lines to the MAP sensor.
7. Check sensor supply voltage and signal circuits with a multimeter, following the manufacturer's wiring data for that model.
8. Check for other codes and for any available software updates or technical bulletins for the specific model.

How to fix

• Repair or replace leaking intake hoses, clips or manifold gaskets.
• Clean the MAF sensor with a suitable cleaner, or replace it if readings are still implausible.
• Replace a faulty MAP sensor or repair its vacuum line.
• Clean the throttle body and carry out the throttle adaptation or relearn if the manufacturer requires it, or replace a faulty throttle body or sensor.
• Repair damaged wiring or connectors, then clear the codes and road test to confirm the fault does not return.

Can I keep driving?

Nearby codes

• P0067GenericAir Assisted Injector Control Circuit High
• P0069GenericManifold Absolute Pressure - Barometric Pressure Correlation