Limp In Mode

If the information from the Manifold Absolute Pressure Sensor, Throttle Position Sensor and Coolant Temperature Sensor fails certain on board diagnostic tests, the logic module goes into a "limp-in" mode, turns on the power loss lamp and substitutes a modified signal in place of the failed one, in order to keep vehicle driveable. The power Loss Lamp, located on the instrument panel, acts as a warning device to inform the operator that a malfunction in the system has occurred and immediate service is required.
If the MAP sensor signal is too low (less than .3 volts) or too high (greater than 4.9 volts) or not changing, fault codes 13 and/or 14 are recorded in memory and the "power loss" lamp is turned "ON". At this time the throttle position and engine speed signals are used by the logic module to generate a modified MAP sensor signal in place of the failed one. While in this "limp-in" mode the AIS (automatic idle speed motor) is driven to its minimum position.
If the Throttle Position Sensor signal is too low (less than .16 volts) or too high (greater than 4.7 volts) fault code 24 is recorded in memory and the "power loss" lamp is turned "ON". At this time the MAP sensor signal is used by the logic module to generate a modified throttle signal in place of the failed one.
If the coolant Temperature Sensor signal is too low (below -60 degrees F) or too high (above 270 degrees F) or changes too fast to be real, fault code 22 is recorded in memory and the "power loss" lamp is turned "ON". At this time the logic module will set in a fixed value in place of the coolant temperature signal.
If these three sensor signals return to within specifications, while the engine is running the power loss lamp will stay "ON", and the system will stay in the "limp-in" mode until the engine is turned off.