E027

ECM Code E027:

DFI ISC Circuit:

DESCRIPTION:

The throttle switch is part of the ISC motor assembly. Pin B of the ISC motor 4-way weatherpack connector is the throttle switch input to the ECM. The ECM provides a 4.5 to 6.0 volt signal to pin B of the ISC. When the throttle lever contacts the ISC plunger, the throttle switch closes, shorting the 4.5 to 6.0 volt signal at pin B to pin A which is a ground. Closed throttle = throttle switch input voltage low. Code E027 is designed to detect a throttle switch that is always open.

TEST CONDITIONS:

Always tested.

FAILURE CONDITIONS:

1. Throttle switch was never closed during the last key cycle.
2. Brake switch was applied during the last key cycle.
3. Throttle switch has not closed in the current key cycle.

ACTION TAKEN:

1. ECM turns on "SERVICE ENGINE SOON" telltale.
2. ECM commands BCM to display "SERVICE SOON" message on CCDIC.
3. ECM assumes throttle switch is close if TPS is less than 12° and the brake switch is closed (not braking).

NOTES ON FAULT TREE:

1. Code E027 due to throttle switch input open or the ISC throttle switch inoperative should result in EI72 not cycling - EI72 will be "HI" at all times.

NOTE ON INTERMITTENTS.

Check for throttle shaft and throttle blades binding, throttle spring weak or distorted, cruise or TV cable binding the throttle linkage, TPS for proper installation. Intermittent code E027 can be induced by resting foot on the accelerator during a key "ON" key "OFF" for 10 seconds, key "ON" cycle.