FALSE CODE 42 RE-ROUTE EST WIRING

MODELS AFFECTED: 1984 LESABRE, ELECTRA, RIVIERA EQUIPPED 5.0L ENGINES (VIN CODE Y)

A false Code 42 can be set on 1984 5.0L engines when the driver turns the engine off and returns the key back to the "on" position within five (5) seconds.

If the key is turned off (engine must stop) and back on within five (5) seconds, the ECM has not had enough time to shut off. As a result, when the key is immediately turned back on with the engine off, the ECM does not see a distributor-reference pulse and, in turn, sets Code 42.

This is a normal condition and should be conveyed to technicians servicing CCC systems and owners that might encounter Code 42 under these conditions. This will reduce customer concerns and unnecessary diagnosis time.

To verify this is a false code, first, the ECM memory should be cleared, per the procedures outlined in the 1984 Chassis Service Manual. Then,the engine started and ignition turned off. Wait ten (10) seconds, and then restart. After five (5) cycles of engine start and "key off" procedure, check for malfunction codes, per instructions in the Service Manual. If none appear, a false Code 42 was set. If a Code 42, or any other codes appeared, they should be corrected per the appropriate diagnostic chart.

A false code 42 may also be caused by the routing of the EST wiring through or around sprk plug ignition wires. The electromagnetic field around the spark plug wires could be causing the false code 42 to be set.

To correct this condition, the EST harness must be routed to the cowling side of the transmission filler tube. On Rivieras, the harness must be routed outboard of the water control valve. The EGR solenoid lead harness must also be routed behind the distributor on Electras and Rivieras.

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.