ECM Code EO27: Open Throttle Switch Circuit: Action:

ECM turns on SERVICE ENGINE SOON light and assumes closed throttle if brakes are applied or TPS position is less than or equal to 18 degrees. ECM also assumes open throttle when brakes are off or TPS position is more than 18 degrees.

The throttle switch is part of ISC motor assembly. Terminal "B" of ISC motor 4-pin connector is the throttle switch input to the ECM. The ECM provides a 4.5-6.0 voltage signal to terminal "B" of ISC. When throttle lever contacts ISC plunger, throttle switch closes, shorting voltage signal at terminal "B" to terminal "A", which is a ground (closed throttle equals throttle switch input voltage low). Code EO27 detects a throttle switch that is always open.

NOTE: Test number refers to test number on diagnostic chart.

Test Number 1) ISC 4-way connector is located at a jumper connector near the alternator.