P0068 Code: MAP/MAF – Throttle Position Correlation
The airflow the engine measures doesn't match what the throttle opening says it should be.
At a glance
Severity: Moderate
- Meaning
- MAP/MAF – Throttle Position Correlation
- System
- Fuel & Air Metering · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $10–$900
- DIY difficulty
- Moderate
The engine computer constantly predicts how much air should enter the engine from throttle angle and rpm, and cross-checks that prediction against the mass airflow sensor, the manifold pressure sensor, or both. P0068 sets when the two disagree beyond a set window, for example lots of measured airflow with the throttle nearly closed, or very little airflow with the throttle wide open. The most common reason is unmetered air: a crack in the intake duct between the MAF and the throttle, a loose PCV hose, or on turbo engines a leaking charge pipe or intercooler boot. A carboned-up throttle body, a skewed MAF or a failing throttle position sensor can create the same mismatch.
Can I keep driving? You can usually drive, but the engine may idle rough, stall when coming to a stop or cut power into a reduced-power mode. Avoid heavy traffic and highway merges until it's checked, since a sudden stall or power cut is the main risk.
How to read P0068
- P Powertrain
- 0 Generic (SAE)
- 0 Fuel/air & emissions (aux.)
- 68 Specific fault
Symptoms
- Check engine light, often with a lean code or a throttle code
- Rough or hunting idle, sometimes stalling at stoplights
- Reduced engine power message or limp mode
- Hesitation when you tip in from a closed throttle
- Whistle or sucking sound from the intake at idle
- Turbo engines: whoosh or hiss under boost from a leaking charge pipe
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Air leak after the MAF: cracked intake boot, loose clamp, split PCV or brake booster hose
- Carbon buildup or wear in the electronic throttle body
- Contaminated or skewed MAF sensor, often after an oiled aftermarket air filter
- Turbo engines: leaking charge pipe, intercooler boot or blow-off valve after the MAF
- MAP sensor or its vacuum port clogged, or MAP hose cracked
- Throttle position sensor signal fault or wiring issue
- Engine computer calibration issue addressed by a software update
Diagnosis step by step
Read freeze frame and companion codes
Note rpm, load, throttle angle and MAF reading at the moment the code set. A code set at idle with high airflow points to a vacuum leak; a code set under load with low airflow points to a restriction, sensor skew or a charge-pipe leak. Lean codes alongside P0068 strongly suggest unmetered air.
Tools: OBD-II scanner
Check idle airflow against displacement
At warm idle with accessories off, MAF flow in grams per second is roughly equal to engine displacement in liters, so about 2 to 3 g/s on a 2.0-liter and 5 to 6 g/s on a 5.3-liter. A reading far below that with a normal idle means air is sneaking in after the sensor or the sensor reads low.
Tools: OBD-II scanner
Smoke-test the intake
Block the air intake ahead of the MAF and feed smoke into the intake duct. Watch the boot between MAF and throttle, the PCV connections, the brake booster hose and the manifold gasket. On turbo engines include the charge pipes and intercooler.
Tools: Smoke machine, Flashlight
Inspect and clean the throttle body
With the ignition off, remove the intake boot and look at the throttle plate edges and bore. A dark ring of carbon changes the airflow at small openings. Clean with throttle-body cleaner on a rag, never force an electronic plate open by hand with the key on, and run the idle relearn if your model requires one.
Tools: Flashlight, Screwdriver
Compare TPS and MAP readings
With the key on and engine off, both throttle position signals should move smoothly and track each other as you press the pedal. At warm idle, manifold pressure is typically 25 to 35 kPa (about 17 to 21 inHg of vacuum). A MAP that sits near barometric at idle means a blocked port or a cracked sensor hose.
Tools: OBD-II scanner, Vacuum gauge
Test the MAF under load
Do a safe wide-open-throttle pull in second or third gear. On a healthy engine, peak MAF flow in g/s comes out at roughly three quarters of the engine's rated horsepower near redline; much lower points to a dirty sensor or a restricted intake. Clean with dedicated MAF cleaner only.
Tools: OBD-II scanner
Where the parts are
- 1MAF sensor
- 2Turbocharger
- 3Throttle body
- 4Intake manifold
- 5Fuel injector
- 6EGR valve
- 7Fuel pump
- 8Thermostat
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Tighten clamp or replace cracked intake boot | Yes | $15–$120 |
| Clean throttle body and run idle relearn | Yes | $10–$150 |
| Replace MAF sensor | Yes | $120–$400 |
| Replace charge pipe or intercooler boot (turbo engines) | Yes | $120–$500 |
| Replace electronic throttle body | No | $300–$900 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Chevrolet
On GM engines with electronic throttle control, P0068 commonly shows up together with throttle codes and a Reduced Engine Power message. A dirty throttle body, a cracked intake boot or a corroded throttle connector are the usual finds before anyone should replace the engine computer.
Field data
| Chevrolet | 4 | Impala, Malibu, Tahoe |
|---|
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Will fail
With the check engine light on, the car fails OBD-II emissions testing in states that require it. Lean-running from an intake leak can also keep the fuel system monitor from completing.
Frequently asked questions
Is P0068 a turbo code?
No, it can appear on any engine with a MAF or MAP sensor and electronic throttle. On turbo engines it's grouped with boost problems because a leaking charge pipe after the MAF is a common trigger, but most cases on non-turbo cars are simple vacuum leaks or a dirty throttle body.
Can an aftermarket air filter cause P0068?
It can. Oiled cotton filters that were over-oiled leave a film on the MAF sensing element, so it under-reads airflow. The mismatch against throttle angle then trips the code. Clean the sensor and let the filter's oil settle properly next time.
Why does my car stall right after P0068 appears?
When the computer no longer trusts the airflow reading, it may switch to a backup fuel and throttle strategy that's less precise at idle. Combined with the vacuum leak that often caused the code, the idle can dip too far and stall.
Will cleaning the throttle body fix it?
Only if carbon is the problem. It's worth doing when you can see a dark ring around the plate, but if the smoke test shows a leak or the MAF reads low at idle, cleaning alone won't stop the code from returning.