ROUGH IDLE,NO START, CODES E12,E23,E28 OR E30

MODELS AFFECTED: 1988 DE VILLES, FLEETWOODS, ELDORADOS, AND SEVILLES

Some 1988 DeVilles, Fleetwoods, Eldorados, or Sevilles may experience one or more of the following symptoms:

o Rough idle, may be intermittent when cold, hot, or under high electrical loads (i.e., A/C compressor, rear window defogger on).

o Erratic ignition secondary scope patterns (i.e., double firing lines).

o Detonation (spark knock) at idle or acceleration.

o Intermittent no start or no crank.

o ECM trouble code E12, E23, E28, or E30.

Any of the above conditions may be caused by high resistance in the vehicle ground eircuits, which can disturb the ECM ground, circuit 450. High resistance may be due to a loose or corroded connection, or an open or frayed circuit in the battery negative cable.

If the condition is intermittent, checking the resistance of the ground circuit may not be an effective diagnostic test to confirm a ground problem.

Therefore, to diagnose this condition:

1. Install a jumper wire from the generator frame to the negative post of the battery.

o If the condition is still present, refer to the appropriate section of the 1988 Cadillac Service Information Manual for diagnosis.

o If the condition is eliminated, remove the jumper and go to step 2.

2. Check for loose or corroded ECM or engine ground connections.

NOTE: All ground connections must be CLEAN as well as tight. Disassembly of the ground is required to accurately check for corrosion and/or painted surfaces. If corrosion or paint is present on either mating surface, it should be cleaned with a wire brush before being reinstalled. A starwasher should also be installed for all metal to metal electrical joints.

1988 Service Information Manual page numbers have been included to show the ground locations.

o DeVille/Fleetwood

GlOO: Engine compartment ahead . . . . . . . . . . . Page 8A-201-3, of left hand wheelhouse Figure A

G101: Right hand side of . . . . . . . . . . . . . Page 8A-201-0, engine on generator mounting bolt Figure A

G105: Right hand side of . . . . . . . . . . . . Page 8A-201-5, engine compartment on fender stud Figure A

G110: Right hand side of . . . . . . . . . . . . . . . .Page 8A-201-0, engine below rear valve cover Figure B

NOTE: The proper installation sequence is: the power steering bracket, O2 sensor/ECM ground eyelet, starwasher, and nut.

Negative Battery Cable - on stud near starter motor.

o Eldorado/Seville

GlOO: Right hand front of . . . . . . . . . . . . . Page 8A-201A-2, engine compartment in front of battery Figure A, Item 17

G101: Top right hand side of engine on generator bracket, not shown in manual

G102: Right hand end of . . . . . . . . . . . . . . . . Page 8A-201-0 rear cylinder head Figure A

G103: Lower front of engine . . . . . . . . . . . . . . .Page 8A-201-1 right of starter solenoid Figure C

ISO Ground Junction Block: Right hand side . . . . . . Page 8A-201-3 of engine compartment Figure A

3. If the condition is still present and the appropriate ground connections are clean and tight, replace the battery negative cable.

For warranty purposes use Labor Operation N0126 at .2 hour for DeVilles and Fleetwoods and .7 hour for Eldorados and Sevilles.

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.