Action Taken
WARNING: This page is about a different car, the 1990 Cadillac Fleetwood and 1990 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
- ECM turns on SERVICE SOON light. ECM assumes throttle switch is closed if TPS is less than 18 degrees and brake switch is open (braking).
- ECM assumes that throttle switch is open if TPS is greater than 18 degrees or brake switch is closed (not braking).
NOTE:
When Code E27 is stored hard, throttle switch status light (OFF) will display the "failsoft" or substituted throttle switch status. To display actual throttle switch status, enter diagnostics and clear codes.
The throttle switch is part of ISC motor assembly. Terminal "B" of ISC motor 4-way weatherpack connector is throttle switch input to ECM. The ECM provides a 5-volt signal to terminal "B" of ISC. When throttle lever contacts ISC plunger, throttle switch closes, shorting 5-volt signal at terminal "B" to terminal "A", which is a ground (closed throttle equals throttle switch input voltage low).
NOTE:
Test numbers refer to test numbers on diagnostic chart.
Test Number 1) If throttle switch test E.7.2 does not pass, use chart E.7.2 to diagnose.
Test Number 2) If throttle switch E.7.2 cycles, Code E27 should not remain as a hard code.