E027

TEST CONDITIONS
Always tested.

FAILURE CONDITIONS
1. Throttle switch was never closed during the last ignition cycle in which the engine was running and the brake was depressed;
2. Throttle switch has not closed in the current key cycle.

ACTION TAKEN
1. ECM turns on "Engine Control System Fault" telltale;
2. ECM commands BCM to display "Service Soon" message on Driver Information Center (DIC);
3. EGR is disabled;
4. ECM assumes the throttle switch is closed if brake is applied and TPS 18 degrees;
5. ECM assumes the throttle switch is open if brake is not applied;
6. ECM assumes the throttle switch is open if TPS is greater than 18 degrees.

DESCRIPTION
The throttle switch is part of the ISC motor assembly. The ECM provides a 5 volt reference on CKT 427 to Pin B of the ISC weather pack connector. When the contacts the ISC plunger, the throttle switch closes, connecting Pin B to ground at Pin A. When the throttle switch is closed, throttle switch input voltage is low (ground). Code EO27 is designed to detect a throttle switch that is always open; throttle switch never closes.

Notes on Fault Tree
1. Checking for throttle switch status light to cycle. If light does not cycle, follow ECM input EI72 trouble tree.

Notes on Intermittents
Check for throttle shaft and throttle blades binding, throttle spring weak or distorted, cruise or TV cable binding throttle linkage, TPS for proper installation.

Intermittent Code EO27 can be induced by resting foot on the accelerator during a key "ON" key "OFF" for 10 seconds, key "ON" cycle.