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Latest News MAP Sensors Testing What a technician needs to know when testing the MAP sensor on a naturally aspirated intake system. (0 – 1 Bar). As covered in detail in the previous MAP sensor article, we know that the MAP sensor converts the manifold pressure to a voltage or frequency output signal to assist the PCM in fuel and timing control but the information may also be utilised for the control of other engine systems. Multiple engine conditions may cause the required MAP sensor signal to alter which affects engine fuelling and in turn performance and emission levels. Typically Common:
The importance of thorough electrical testing. In many cases, a DTC (fault code) may suggest that the MAP sensor may be potentially faulty but further testing confirmed the condition was the result of other variants. In other cases, the MAP sensor may not set a DTC (fault code) unless severely out of range as the operating range is quite broad but the effect of a slight MAP signal variation may cause the PCM to alter engine fuel and timing control which can have an effect on engine performance and emissions. This may be evident during short- and long-term trim measurements when using a suitable scanner. Note: A technician’s thought process must be flexible when interpreting test data during diagnosis. Specific MAP sensor possible fault conditions or areas that may affect MAP signal that require attention for thorough electrical testing:
Engine backfiring, carbon build up and possible fluid build-up on some MAP sensors are typical causes of out of range or output signal plausibility failures. Thorough MAP signal testing. Typically, monitoring serial data information with a suitable scanner may be enough to guide the technician in the next stage required in the MAP sensor diagnostic or testing process. Confirmation: Further confirmation: Typical test procedure: (3 terminal MAP sensor)
Monitoring the scan tool results should indicate Atmospheric pressure. (101Kpa = 1 Bar) Note: this would indicate that the “supply voltage”, “Ground circuit” and “MAP sensor plausibility” is acceptable and is received by the PCM.
Note: the “cylinder fuel supply” control relies mainly on MAP and Coolant sensor output signals, so accuracy is essential for correct engine fuelling. Therefore, any DTC condition referring to fuelling problems / Trims would require thorough testing of the MAP sensor plausibility.
Initial Crank / Start monitoring expectations.
Engine stabilised after starting.
Wide Open Throttle test (snap acceleration) Profile requirements:
Note: The accelerator release results in a higher that idle vacuum profile resulting when throttle valve closes. The Idle stabilising profile can also be seen which can be used to monitor signs of any air leaks and any idle control system irregularities. Engine switched OFF from Idle condition. (back to static “engine manifold” atmospheric pressure). Note: a four terminal MAP sensor integrates an air intake temperature sensor that utilises the extra terminal. Typical MAP sensor test data requirements to ensure sensor plausibility.
The Premier Auto Trade Sensor range includes 139 MAP Sensors (MAP) from the world’s leading manufacturers, covering almost 9 million vehicle applications in Australia and NZ. When you supply and fit products from Premier Auto Trade you can expect a product designed and tested to the vehicle manufacturer’s specifications offering OE form, fit and function. Premier Auto Trade distributes products throughout Australia via a network of specialised resellers and leading automotive groups. |
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