CODE E30/E030 AFTER COLD START REPLACE ISC MOTOR

CODE E30/EO30 AFTER A COLD START - REPLACE ISC MOTOR

VEHICLES AFFECTED: 1988 C/E/K 4.5 (VIN CODE 5) ----------------- Some 1988 DeVilles, Fleetwoods, Eldorados, or Sevilles may experience a "Service Soon" light/message which comes on after a cold start due to a code E30. Code E30 will bring the "Service Soon" light/message on for the entire key cycle. Code E30 after a cold start can be caused by a low gain (slow moving) ISC motor. A low gain motor will not move as far as expected for a given ISC pulse from the ECM. This causes the actual rpm to be different than the rpm the ECM expects to see. A low gain motor will most likely set a code E30 after a cold start when the ISC motor is most active. Also, a code E30 due to a low gain ISC motor will NOT result in a driveability condition (idle surge, rough idle, etc.).

To confirm that a low gain ISC motor is the cause of code E30, perform the following test:

NOTE: This test should be performed with the engine cold. Also, test in the morning to ensure the coldest possible outside temperature.

1. Key on, engine off, turn the climate control off.

2. Start engine. Do not open throttle switch (foot off gas pedal).

3. Leave transmission in park.

4. Allow engine to idle for at least 45 seconds.

5. If the "Service Soon" light/message comes on and a code E30 is set, replace the ISC motor, P/N 17111170.

NOTE: When replacing an ISC motor for this condition, make sure the Julian Date code is greater than 147, refer to Figure 1. The date code is on a sticker on the ISC motor.

CODE E30/E030 AFTER A COLD START - REPLACE ISC MOTOR

6. If the "Service Soon" light/message does not appear, or if a code E30 is set but is accompanied by an engine driveability condition (idle surge, rough idle, etc.), refer to the DFI system check in Section 6E-A of the appropriate 1988 Service Information Manual.

NOTE: The diagnostic chart for ECM code E030, Idle Speed Control Problem, on page 8D1-47 of the 1988 Eldorado/Seville Service information Manual, directs you in several places to "Go to E007, ISC Cycling". This should read "Go to E006, ISC Cycling". Additionally, the diagnostic chart for ECM code E055, TPS Misadjusted, on page 8D1-77, directs you to "Select ECM Output E007". This should read "Select ECM Output E006". Revised diagnostic charts are attached. Please note these changes in your copy of the Service Information Manual.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.