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Error Code P0068 is defined as Manifold Absolute Pressure sensor (MAP)/ Mass Air Flow (MAF) Throttle Position Correlation. Meaning, the PCM (Powertrain Control Module) has detected an inconsistency in the positioning of the throttle sensor with the MAF. This, however, is a generic term for error code, which means it applies to all makes and models of vehicles since 1996 to present. However, this also means different manufacturers may have a different definition and specific information regarding this error code.
Error Code P0068 means the PCM has detected an excessive input voltage signal degree variation from the TIPS (Throttle Position Sensor) compared to the voltage input signals of MAF sensor and the MAP sensors. The PCM reads and analyzes these individual engine drivability sensor signals, then compares them both to help develop the delivery of fuel and ignition timing tactics. The PCM depends on three sensors – namely the MAF, MAP and Throttle Position sensor. The engine contains a lot of sensors, but these three are associated with the error code.
The PCM also uses this information to ensure that the fuel-to-ratio level is always constant, controllable and acceptable to limitations fuel-to-air. If the voltages detected for these three sensors (triangulated) fail to correspond with the programmed parameters, even just one of the three sensors, for a specific period of time or specific engine revolutions, the trouble code P0068 will be registered.
Aside from the activation of the Check Engine light, this error code also causes an overboost condition, which includes the symptoms:
- Drastic reduction of fuel efficiency
- Lack or reduced engine performance
- Rough idle
- Hesitation upon acceleration
The most common causes for this error code are wiring trouble in the MAP and/or MAF sensor or other mechanical issues. Other possible causes include:
- Faulty or damaged sensor
- Leak in the intake manifolds or its sections
- Dry air cleaner
- Vacuum leaks in the MAF sensor and intake manifold
- Loose or cracked hoses in the intake manifold
- Airflow obstruction
- Cooked runner at the back of the throttle body
- Corroded or poor electrical connectors
- Obstruction in the hose in between the MAP sensor and intake manifold
- Defective electronic body
How to Check
Mechanics diagnose this error code by checking on the MAP sensor, MAF sensor, Throttle Position sensor, Intake Manifold, as well as the Air Induction System. For its sensors, qualified mechanics will ensure all sensors are properly installed and tested for functionality. They will also check the engine for signs of vacuum leaks in its throttle body, intake manifold, and air induction system through the vacuum gauge or through a smoke test.
How to Fix
This simple diagnosis above could easily reveal the source of the problem of the error code P0068. However, as said earlier, qualified mechanics may need to conduct specific diagnostic steps, depending on the make and model of the vehicle. Also, mechanics will use other tools and testing equipment, such as the volt-ohmmeter, carburetor cleaner can, meter’s wire-piercing probe and an intake cleaner can.
A clogged or dry air cleaner may cause this error code. Thus, you will need to check the air cleaner element (engine off of course). Look for any signs of clamps or leaking in the pipe starting from the MAF to the Throttle body.
Then, check the vacuum lines in intake manifold for any cracks, obstructions, or looseness, as these can cause vacuum loss.
Detach every sensor and check the connector for signs of corrosion and bent pins that are pushed out.
Look for leaks manifold in the intake and clean the carburetor using the carburetor cleaner. The engine RPM will change noticeably after a short shot of the carburetor cleaner over a leak. Then, hold the can at arm’s length to keep it away from your eyes and spray all connection points to the manifold for leaks.
Get a hold of the clamp loose on the pipe that connects the MAF to the throttle body. Check the throttle body for signs of coated coke (black greasy substance). If there is coke, pinch the tube from the intake cleaner bottle between the pipe and the throttle body. Then, push the pipe and start the engine. Start spraying until you use up the can. Remove the pipe and then connect it to the throttle body again.
If the repairs above don’t seem to solve the problem, then you obviously need the help of a qualified mechanic, as they can conduct further troubleshooting and repairs using special tools and equipment, especially with the three sensors.