ROUGH IDLE,NO START, CODES E12,E23,E28 OR E30
ROUGH IDLE, INTERMITTENT NO START
VEHICLES AFFECTED: 1988 C/E/K W/4.5
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 circuits, 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
G100: Engine compartment ahead of left hand wheelhouse-pg 8A-201-3A
G101: Right hand side of engine on generator mounting bolt-pg 8A-201-OA
G105: Right hand side of engine compartment on fender stud-pg 8A-201-5A
G110: Right hand side of engine below rear valve cover-pg 8A-201-OB
NOTE: The proper installation sequence is: the power steering bracket, 02 sensor/ECM ground eyelet, STARWASHER, and nut.
Negative Battery Cable - on stud near starter motor.
o Eldorado/Seville
G1OO: Right hand front of engine compartment in front-pg 8A-201A-2A, of battery.............................Item #17
G101: Top right hand side of engine on generator bracket, not shown in manual
G102: Right hand end of rear cylinder head.........page 8A-201-OA
G103: Lower front of engine right of starter solenoid......pg 8A-201-lC
ISO Ground Junction Block: Right hand side of engine.....pg 8A-201-3A compartment
3. If the condition is still present and the appropriate ground connections are clean and tight, replace the battery negative cable.
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.
