Fault code P0068 is called “MAP/MAF โ Throttle Position (TPS) Correlation” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P0068
Fault code P0068 is generic and refers to an engine management problem. Means that there is a discrepancy in the air volume reading between the vehicle sensors and the intake manifold.
The PCM relies on three sensors to determine airflow volume in order to calculate fuel delivery tactics and select injection timing. These sensors include the mass air flow sensor (MAF), throttle position sensor (TPS), and manifold pressure sensor (MAP).
The mass air flow sensor (MAF) is located between the air cleaner and the throttle body. Its job is to signal the amount of air passing through the throttle body. To do this, a thin wire of resistance, the thickness of a hair, is stretched at the inlet to the sensor.
The throttle position sensor (TPS) is located on the opposite side in the throttle body. When closed, the throttle valve prevents air from entering the engine. The air required for idling is bypassed, through the idle control valve.
The manifold absolute pressure sensor (MAP) plays a dual role in this process. It determines the pressure in the manifold, corrected for air density due to temperature, humidity, and location above sea level.
It is also connected to the intake manifold via a hose. When the throttle suddenly opens, the pressure in the manifold drops sharply and rises again as the air flow increases.
The engine control computer needs all three of these sensors to accurately determine when the injectors are open. And also the amount of ignition advance needed to maintain the 14.5/1 fuel ratio.
If for any reason one of these sensors causes a discrepancy between the readings of the others. The computer will not be able to make proper adjustments and will generate fault code P0068.
Symptoms of vehicle malfunctions
The main signal that an error P0068 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- The “Check engine” control lamp on the control panel will illuminate (the code will be stored as a fault).
- Other related fault codes may also be present (e.g. sensor faults).
- Floating revolutions, as well as attempts to stall at idle.
- The engine cannot be accelerated and throttle response is unresponsive.
- Decrease of the engine power.
- Increased fuel consumption.
The fault P0068 is considered to be quite serious, as its occurrence may cause problems with the operation of the car engine. To avoid serious engine damage, if this code is found, it is recommended to eliminate it as soon as possible.
Factors that can cause this error code
The error code P0068 can mean that one or more of the following problems have occurred:
- Faulty MAP, MAF or TPS sensor.
- Poor quality or corroded electrical connectors.
- Vacuum leaks due to cracks, tears, or other damage to vacuum lines and hoses.
- Clogged intake line behind throttle body.
- Clogged air filter.
- Obstruction of air flow.
- Faulty electronic throttle body.
- Sometimes the cause is a defective PCM module.
How to fix or reset OBD-2 code P0068
Some suggested steps for troubleshooting and fix the error code P0068:
- Read all stored data and error codes with an OBD-II scan tool.
- Clear the error codes from the computer memory.
- Test-drive the vehicle to see if fault P0068 appears again.
- Visually inspect the wires and connectors to the MAP, MAF, and TPS sensors.
- Test the sensors themselves.
- Inspect vacuum lines and hoses for cracks, tears, or other damage.
- Check the air filter as well as the air passages for normal air flow.
- If the error persists, check the PCM module.
Diagnose and repair of problems
Use the scan tool to retrieve and record all trouble codes, then clear them and test drive the vehicle. After the test drive, reconnect the scan tool and check if code P0068 has returned.
Codes that don’t return are usually called intermittent codes and are often harder to diagnose.
Any diagnosis begins with a visual inspection of the relevant components, connectors and electrical circuits. Items that are corroded, damaged, or simply disconnected should be repaired before continuing with the diagnosis.
Make sure that the vehicle battery is fully charged and that cable connections are corrosion-free and secure. Low battery voltage will distort the real-time test data and make proper diagnostics nearly impossible.
Checking the MAP sensor
The manifold absolute pressure sensor (MAP), is used by the PCM to determine the degree of vacuum pressure in the intake manifold when the engine is running. TPS position, engine RPM level, and MAF sensor input voltage signal. Used in conjunction with the MAP sensor input signal to calculate the engine control strategy.
This sensor is typically screwed in or inserted directly into the intake manifold and sealed to prevent vacuum leakage. The MAP sensor uses a variable resistance to change the input signal voltage reading for the PCM.
Refer to the service manual for sensor and circuit resistance information. After that, check the resistance and replace faulty components if necessary.
MAF sensor check
The mass air flow sensor (MAF) is usually a vane-type sensor with an open heater element. Battery voltage is used to maintain the high temperature of the element.
As airflow increases, the temperature of the heated element drops, which is recognized by the PCM as an increase in airflow in the intake manifold. The PCM uses this input data to develop a fuel delivery strategy.
Since the MAF sensor reflects different intake air intake intensities. Use a multimeter to check real-time voltage readings at manual throttle control.
Measure the sensor resistance values and compare them to the manufacturer’s specifications. If necessary, replace sensor or repair open circuits and connectors.
TPS testing
Modern throttle position sensors (TPS) are of the non-contact type. They can include Hall effect, magnetoresistive, and inductive sensors.
Typically, a 5 volt reference signal (from the PCM) and battery ground are applied to the TPS. The signal circuit allows a voltage signal from the TPS to be applied to the PCM.
The TPS is designed to allow the voltage input signal to change at the PCM. The PCM typically receives a voltage signal in the range of 0.5 to 5.0 volts when the throttle is opened.
Check for a reference voltage signal and a ground signal. If these signals match the manufacturer’s specifications, check the voltage input signal to the PCM during manual throttle control.
Observe real-time voltage data and pay special attention to failures and other inconsistencies. Consult the manufacturer’s service manual for application-specific voltage and resistance values.
After completing the repair, use the scan tool to remove code P0068, and then test drive the vehicle to verify that the repair was successful.
On which vehicles does this problem occur most frequently
Fault code P0068 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Audi (A4,ย A6, Q5)
- Buick (Verano)
- Chevrolet (Cobalt, Suburban, TrailBlazer)
- Chrysler (300M)
- Ford (Fiesta)
- Hyundai (Accent)
- Jeep (Commander)
- Kia
- Mercedes-Benz
- Opel (Astra, Corsa)
- Skoda (Fabia, Yeti)
- Vauxhall
- Volkswagen (Beetle, Touareg)
Fault code P0068 can sometimes be found with other errors. The most common are the following: P0010, P0016, P0017, P0036, P0069, P0074, P0101, P0106, P0121, P0335, P0344, P0513, P1101, P228C, P2431, U0100.
