Operation CHARM: Car repair manuals for everyone.

E027

Diagnostic Chart.:




ISC Circuit:






DESCRIPTION:

The throttle switch is part of the ISC motor assembly. The PCM/ECM provides a 5.0 volt signal on CKT 427. When the throttle lever contacts the ISC plunger, the throttle switch closes. When the throttle switch is closed the input voltage is low. Code E027 is designed to detect a throttle switch that is always open.

TEST CONDITIONS:

Continuous monitoring.

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. PCM/ECM turns on "SERVICE ENGINE SOON" telltale.
2. PCM/ECM assumes throttle switch is closed if brake is applied and TPS is less than 18°.
3. PCM/ECM assumes throttle switch is open if brake is not applied and TPS is greater than 18°.

NOTES ON FAULT TREE:

1. The ISC four way connector is located at a jumper connector. This connector is located by the generator.

NOTE ON INTERMITTENTS.

Check ISC plunger mechanical operation. Check throttle body for coking, throttle spring, cruise and TV cable for binding.