OBD I/M System Monitors Not Supported (05-06-04-028)

Publication date: 2005-04-18
Reference number: 05-06-04-028

OBD I/M System Monitors Not Supported

TECHNICAL SERVICE BULLETIN

Reference Number(s): 05-06-04-028, Date of Issue: April 18, 2005

Affected Model(s):

1999-2000 Buick Century, LeSabre, Park Avenue, Regal, Riveria; 1999-2000 Chevrolet Camaro, Lumina, Malibu, Monte Carlo, Venture; 2000 Chevrolet Impala; 1999 Oldsmobile Cutlass, Eighty Eight; 1999-2000 Oldsmobile Alero, Intrigue, Silhouette; 1999-2000 Pontiac Bonneville, Firebird, Grand Am, Grand Prix, Montana, Trans Sport; with 3.1L, 3.4L, 3.5L or 3.8L V-6 Engine (VINs J, E, H, K, 1 - RPOs LG8, LA1, LX5, L36, L67)

SERVICE INFORMATION

A scan tool system status display will indicate whether the major OBD monitors are Complete, Not Complete or Not Supported.

OBD system monitors are grouped as those that run continuously during a trip or those that do not run continuously during a trip (non-continuous). Continuously running OBD system monitor status should always indicate that the monitor is complete.

Several U.S. states require that the above vehicles' major On-Board Diagnostic (OBD) monitors have completed prior to an OBD I/M emission inspection. Some areas may reject a vehicle from testing if certain non-continuous OBD monitors are not complete.

When scanning the system status on the vehicles identified above, it may have been noted that the scan tools or emission test equipment will incorrectly indicate the OBD system status as Not Supported for the continuously running monitors (Misfire, Fuel System, and Comprehensive Components). There is not a fault with the diagnostic system or the vehicle and repairs should not be attempted.

Further, continuous monitor system status for gasoline engines is not considered when preparing for an OBD I/M emission inspection. A vehicle with the MIL commanded on for a continuous system monitor, or for any reason, should be serviced.