Safari Van M V6-262 4.3L VIN Z TBI (1990)
Camshaft Gear/Sprocket: All Technical Service Bulletins
Engine Cam/Crankshaft Gear - Misorientation
ENGINE CAM GEAR MISORIENTATION
1989 M-VAN & 1990 G-VAN, M-VAN, C/K TRUCK AND S/T TRUCK WITH 4.3L (RPO LB4) V-6 ENGINE
General Motors has determined that certain 1989 M-Vans and 1990 G-Van, M-Van, C/K & S/T trucks equipped with 4.3L V-6 engines (RPO LB4) may
have been built with the engine cam gear misoriented to the crankshaft gear This mis-indexed cam can result in a lack of performance or backfire.
Additionally, the emissions performance of these vehicles may be affected. To correct this condition, an electronic scanning procedure to identify
affected engines will be performed. Once identified, dealers will reorient the camshaft.
Involved are certain 1989 M-Vans and 1990 GVan, C/K & S/T trucks equipped with 4.3L V-6 engines (RPO LB4) and built within the following VIN
The specific vehicles involved in this campaign have been identified by Vehicle Identification Number Computer Listings. These listings are furnished to
all involved dealers with the campaign bulletin.
DEALER CAMPAIGN RESPONSIBILITY
Dealers are to service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership, from this time
forward. Whenever a vehicle subject to this campaign is taken into your new or used vehicle inventory, or it is in your dealership for service in the future,
you should take the steps necessary to ensure the campaign correction has been made before reselling or releasing the vehicle. Owners of vehicles
recently sold from your new vehicle inventory are to be contacted by the dealer and arrangements made to make the required correction according to
instructions contained in this bulletin. If no owner's name and address were available to GMC Truck Division at the time of campaign initiation, the
dealer will determine the owner's name and address from the dealership sales records. Please provide this information directly on the second copy of the
listing next to the applicable VIN so that our records may be updated and the appropriate notification mailed to the owner. This second copy should then
be submitted to the address listed below in the previously supplied yellow campaign envelopes.
Owners will be notified of this campaign on their vehicles by GMC Truck Division (see copy of Owner Letter included with this bulletin). A listing of
owner names and addresses has been furnished to the involved dealers to enable dealers to follow up with owners involved in this campaign. This listing
may contain owner names and addresses obtained from State Motor Vehicle Registration Records. The use of such motor vehicle registration data for
any other purpose is a violation of law in several states. Accordingly, you are urged to limit the use of this listing to this campaign.
Connect SCAN tool or CAMS machine to vehicle. Make sure scan tool is in ROAD TEST mode. If using a TECH 1 scan tool, it should be set up
to display BLOCK LEARN (BLM) values and CLOSED/OPEN LOOP status simultaneously. This can be done by scrolling through the
preprogrammed pairs of parameters with YES or NO key until a pair is found with BLOCK LEARN. Fix BLOCK LEARN by pressing "FO" if
BLOCK LEARN is top parameter, "F1" if it is bottom parameter. Then continue scrolling other half of the display with either YES or NO key
until CLOSED/OPEN LOOP status parameter is displayed. To "unfix" top parameter, press "F1." Press "FO" to unfix" lower parameter
If using a CAMS machine, select Dynamic Display Option. This will display both BLOCK LEARN (BLM) and OPEN/CLOSED LOOP status.