INTERMIT BCM CODES B446/B449/B450 (INSTALL BCM SERV. PROM)

SUBJECT: INTERMITTENT BCM CODES (INSTALL NEW BCM SERVICE EPROM's) B446 - LOW A/C REFRIGERANT B449 - A/C HIGH SIDE OVERHEATED, A/C OFF B450 - ENGINE OVERHEAT, A/C OFF

MODELS AFFECTED: 1993 ALLANTES

This bulletin supersedes Service bulletin T-93-7 which should be discarded. This bulletin is being revised to clarify parts replacement procedure, add a NOTE, and change the warranty statement.

Some 1993 Allantes may intermittently exhibit the following BCM diagnostic codes:

B446 - "Low A/C Refrigerant" may be intermittently displayed during mild ambient (45 degrees Fahrenheit to 65 degrees Fahrenheit) temperatures.

B449 - "A/C High Side Overheated, A/C Off" may be displayed during high ambient temperatures when vehicle is idled for several minutes.

B450 - "Engine Overheat, A/C Off" may be displayed during high ambient temperatures when vehicle is at idle or driven at very low speeds for extended periods of time.

The following service EPROM's will correct calibrations for the B449 and B450 diagnostic codes and eliminate the B446 code:

Broadcast Broadcast Old EPROM Code I.D. New EPROM Code I.D. --------- --------- ---- --------- --------- ---- P/N 16177286 (red) BAYY 7236 P/N 16185967 BCXW 4146 P/N 16177283 (gray) BAYY 7236 P/N 16185968 BCXW 4146

NOTE: To properly repair the above condition(s) both EPROM's must be replaced. The black EEPROM does EEPROM need to be replaced.

The new service EPROM's also contain adjustments to prevent the PCM snapshot mode display of POOO and corrections to the program which may prevent the display of "Very Low A/C Refrigerant, A/C Off" when diagnostic codes B447 or B448 are detected. The minimum blower motor voltage is increased from 4 V to 4.5 V to increase air flow at low blower speed.

Parts are currently available from GMSPO.

For warranty purposes use Labor Operation N4801 for .7 hour.

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.