13 No Change In MAP From Start to Run - (P 1297)

13 NO CHANGE IN MAP FROM START TO RUN - (P 1297)





The Manifold Absolute Pressure (MAP) sensor is mounted directly to the plastic intake manifold, between the runners for cylinders 1 and 2. It serves as a Powertrain Control Module (PCM) input at pin 29, receiving 5 volts from the PCM at pin 43, with sensor ground at pin 51. When the key is turned on, the MAP sensor pulls the voltage down. The amount of voltage drop is based on the barometric pressure of the day (key-on baro. reading). This value is then stored in the PCM's memory, where it can be used to perform several calculations, including the pulse-width calculation. When the engine is started, the manifold pressure should drop, causing the MAP sensor's voltage to be pulled even lower. As the load on the engine increases, the pressure in the manifold increases, causing the voltage drop at the MAP sensor to decrease. At wide open throttle (WOT), the pressure in the manifold should be at barometric pressure again. During WOT, the PCM is programmed to update its barometric pressure reading stored from the initial key-on reading, and it updates again, every time WOT is indicated.

ENABLING CONDITIONS
This test is enabled by meeting the following conditions:
- The PCM must not be in the start mode
- The PCM can not be in the limp-in mode from another MAP sensor fault
- RPM is within 64 RPM of the target idle
- Vehicle cannot be moving

If the PCM receives information from the MAP sensor that the barometric pressure is greater than 27.56 in. of mercury, then the PCM must register at least a 3.86 in. of mercury change from the recorded barometric pressure reading, while the engine is running at idle. If the barometric pressure reading is less than 27.56 in. of mercury, the PCM must register at least a 0.12 in. of mercury change from the recorded barometric pressure reading, while the engine is running at idle. (Virtually any change at all will allow the test to pass.) If this does not occur, the PCM assumes that the sensor is no longer able to recognize the actual pressure in the manifold, and enters the limp-in mode. While in limp-in, the PCM uses the throttle position sensor and engine RPM to estimate MAP values.

A single test failure lasting at least two seconds causes the MIL to illuminate and the DTC to be stored in the PCM's memory.

MAP sensor malfunction could be possibly caused by problems with any of the following components:

- MAP sensor
- MAP sensor wiring and related connectors
- O-rings around the MAP sensor (damaged or missing)
- Manifold around MAP sensor (damaged)