P0068
UniversalManifold Absolute Pressure/Mass Air Flow - Throttle Position Correlation
Medium SeverityThe engine computer (PCM) has detected a discrepancy between the expected air intake readings from the MAP or MAF sensor and the actual throttle opening reported by the Throttle Position Sensor. This inconsistency can lead to incorrect fuel delivery and ignition timing, resulting in various driveability problems and reduced engine performance.
⚠️ Before You Begin (Safety First)
Always exercise caution when working on a vehicle. Ensure the engine is off and cool before inspecting components. Disconnect the battery's negative terminal before performing any electrical work to prevent accidental shorts or injury. Allow hot engine components to cool before touching them.
Common Symptoms
- Check Engine Light illuminated
- Rough idle or engine stumbling
- Engine stalling, especially at idle or low speeds
- Poor acceleration or hesitation
- Reduced engine power
- Decreased fuel economy
Common Causes
- Vacuum leaks in the intake system or vacuum lines
- Dirty or faulty Manifold Absolute Pressure (MAP) sensor
- Dirty or faulty Mass Air Flow (MAF) sensor
- Faulty Throttle Position Sensor (TPS)
- Wiring issues or poor electrical connections to the MAP, MAF, or TP sensors
- Restricted air intake system (e.g., clogged air filter)
- Faulty Powertrain Control Module (PCM) (less common)
Frequently reported on: General/Universal
Diagnostic Steps
- Perform a thorough visual inspection for any obvious vacuum leaks around the intake manifold, vacuum lines, and PCV valve. Listen for hissing sounds.
- Inspect the air filter for excessive dirt or obstructions and clean or replace it if necessary.
- Carefully clean the MAF sensor using a specialized MAF sensor cleaner. Do NOT use other cleaners, as they can damage the delicate sensor elements.
- Inspect the electrical wiring harnesses and connectors for the MAP, MAF, and TP sensors for any signs of damage, corrosion, or looseness.
- If you have access to an OBD-II scanner with live data capabilities, monitor the readings from the MAP, MAF, and TP sensors to identify any erratic or inconsistent behavior.
- After performing any inspections or repairs, clear the P0068 code using an OBD-II scanner and test drive the vehicle to see if the code returns.
👨🔧 When to Call a Professional
If after inspecting for common causes such as vacuum leaks, a dirty MAF sensor, or a faulty throttle position sensor, and clearing the code, the P0068 returns, or if you lack specialized diagnostic tools to accurately test sensor readings, it is best to consult a qualified mechanic. They have advanced equipment to pinpoint the exact source of the correlation issue.
Commonly Asked Questions
Can I drive my car with a P0068 code?
While you might be able to drive, it is not recommended for long distances. The P0068 code indicates an issue that can lead to poor engine performance, increased emissions, and potentially cause your engine to stall, which can be unsafe.
What is the difference between a MAP and MAF sensor and how do they relate to P0068?
The MAP sensor measures manifold pressure, while the MAF sensor measures the mass of air entering the engine. Both provide critical air intake data to the PCM. P0068 indicates that the readings from one or both of these sensors do not correlate correctly with the throttle position.
How do I check for a vacuum leak?
Common methods include listening for a hissing sound under the hood when the engine is running, spraying a small amount of unlit propane or carb cleaner around vacuum lines and intake components (engine RPM will briefly change if a leak is found), or using a professional smoke machine to detect leaks.
How do I properly clean a MAF sensor?
First, disconnect the battery. Then, carefully remove the MAF sensor from the intake system. Using only a specialized MAF sensor cleaner, spray the delicate wires and thermistors inside the sensor. Allow it to air dry completely before reinstalling it and reconnecting the battery.
Could a dirty air filter cause a P0068 code?
Yes, a severely clogged or restricted air filter can impede airflow, affecting the readings of the MAF or MAP sensor. This reduced airflow can create a discrepancy between the expected air intake and the throttle position, triggering the P0068 code.