Manifold Absolute Pressure or MAP
sensors are a major component on fuel injected and later carbureted Harley motorcycles. MAP sensors are used on most modern engines to monitor manifold pressure (vacuum), sending that information back to the electronic control module (ECM). The ECM then determines the correct amount of spark advance and for fuel injection also determines the pulse and amount of fuel based on the MAP and other engine conditions. Other sensors
also play a role in engine management on fuel injected models.
When your Harley MAP sensor
fails or begins to malfunction the ECM will begin to make inaccurate changes to ignition timing and fuel management, resulting in various poor running conditions. These conditions may include:
- Poor fuel economy (MPG).
The ECM may incorrectly read low vacuum and assume the engine is under high load, resulting in providing too much fuel and overly advanced timing.
- Sluggish or lack of power.
If the ECM believes the vacuum is high or under low load it will reduce the amount of fuel and retard spark timing. This would result in poor performance when the MAP sensor fails to notify the ECM of an increase in load.
- Rough Idle.
Insufficient fuel injection (supply or pulse width) can produce a rough idle.
When starting from a stop or rolling on the throttle, you may experience a hesitation or stall if the ECM receives the wrong signal from the MAP.
- Hard starting.
An overly rich or lean mixture caused by faulty data from the MAP sensor will make starting difficult. On a fuel injected Harley if you suddenly need to add throttle to start the engine, this is a common sign of a failing MAP sensor.
- Check Engine Light or trouble code.
A check engine light will appear if the sensor fails or if certain trouble codes have been recorded based on different malfunctions. Trouble codes may not always be recorded by all intermittent failures.
It is also important to check the orange boot seal or o-ring that mates the MAP sensor to the intake manifold. A poor seal not only produces a vacuum leak but may also appear as a sensor failure.
While some sites or articles may suggest different methods of testing a MAP sensor, this can be difficult if the fault is only occurring intermittently. If other faults have been ruled out or trouble codes already indicate related faults, replacement of the MAP sensor
Note that MAP sensors found on 2008-later Touring and Sportster models do not use an analog sensor and therefore cannot reliably be bench tested with a common digital multimeter. Digital MAP sensors require an oscilloscope or specialized scan tool designed to read wave forms. Always consult a qualified technician.
Replacement is straight forward for analog MAP sensors, simply remove the screws that hold the sensor clip, then remove the MAP sensor from the intake manifold. When installing the new sensor always use the new orange seal included and make sure it is firmly seated to avoid vacuum leaks.
Replacing a digital MAP sensor is simple but may also require calibration of the ECM. Digital MAP sensors are also prone to damage by faulty wiring, static discharge, or other conditions. For this reason it is always advisable to have a qualified technician install a digital MAP sensor since most electronic sensors are not warrantied for damage once installed.
Common Trouble Codes for MAP sensor failures
P0106 - MAP Sensor Rate of Range Error (04-06 Carburetor)
P0107 - Map Sensor Failed Open/Low (04-06 Carburetor)
P0107 - Map Sensor Open/Low (EFI)
P0108 - Map Sensor Failed High (04-06 Carburetor)
P0108 - Map Sensor High (EFI)
P0108 can also indicate a failed sensor seal at the manifold.
See our list of Fuel Injection Parts and Oxygen Sensors including other ignition and fuel management system components.
Trouble codes may vary on newer models. Always refer to the factory service manual or consult a qualified service technician.