POSSIBLE FALSE CRT DIAGNOSTIC CODE C339

VEHICLES AFFECTED: 1988 RIVIERA/REATTA

Some 1988 Rivieras/Reattas may display a Trouble Code C339 in the Self Diagnostic System Check. Code C339 is designed to set if data communication between the Cathode Ray Tube Controller (CRTC) and radio microcomputers is lost. For undetermined causes, a C339 code may be indicated when no functional conditions exist. If the radio does seem to operate normally, the code should be cleared and the following diagnostic steps taken:

1. With the radio on, touch the seek key on the Electronic Control Center (ECC). A radio channel change indicates good CRTC-radio communication. If no radio problems have been previously observed and all functions now appear normal, consider the C339 code to be false. No repairs are necessary.

2. If no channel change occurs, first check the connectors into the radio receiver and ensure that good metal contact is being made with each pin. Pay particular attention to the pins marked "DAT" (data) and "GRD" (ground). If all pins seem to be seated properly and the seek function remains inoperable, proceed through the Trouble Code C339 diagnostic chart on pages 8D2-90 and 91 in the 1988 Riviera/Reatta New Product 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.