ECM CODE 20 OPEN FUEL PUMP CIRCUIT
MODELS AFFECTED: 1986 ELDORADO AND SEVILLE
Some 1986 Eldorados and Sevilles which experience an ECM Code E020 may be misdiagnosed when using the diagnostic procedure on pages 8D1-26-29 in the 1986 Eldorado and Seville Final Edition Service Information Manual. Since the oil pressure switch is used as a "BACK UP" it must be disconnected before you begin to diagnose an ECM Code E020.
The fuel pump receives power from two alternate sources; the fuel pump relay and the oil pressure switch. The fuel pump relay is energized by the ECM for two seconds at key "ON" to provide fuel pressure for starting. After the two second fuel pump run, the ECM will not power the relay again until distributor reference pulses are received indicating that the engine is turning (crank or run). The oil pressure switch is provided as a "BACK UP". Normal operating oil pressure will close the oil pressure switch contacts and supply power to the fuel pump.
When diagnosing an ECM Code E020, be certain to disconnect the oil pressure switch. Also, add "Disconnect Oil Pressure Switch" as noted in Figure 1 to the first step of the E020 chart on page 8DI-27 of the 1986 Eldorado and Seville Final Edition Service information Manual.
o Turn ignition "OFF" for 10 seconds. o Disconnect oil pressure switch. o Turn ignition "ON" for 5 seconds o Attempt starting engine
Figure 1 - ECM Code E020 Chart Page 8D1-27
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.
