For 1990-2009 cars

# CRUISE CONTROL INFO. UPDATE MULTIPLE SUBJECTS

CRUISE CONTROL INFORMATION UPDATE - 1982-1983 MODELS

1. CRUISE CONTROL CAUSES UNWANTED 3-2 DOWNSHIFT - 1982-1983 DFI

A condition of an unwanted 3-2 downshift and excessive engine noise occurring during the Cruise Control resume or accelerate modes may be caused by a maladjusted Cruise Control link or chain.

If the transmission shift points are normal when not using Cruise Control, a slight amount of slack (one or two beads or holes) should be added to the Cruise Control linkage. Throttle position (parameter .0.1) should not exceed 600 at any time after resume is depressed at 35 MPH to accelerate to a previously established 55 MPH set speed.

A trade-off exists in that the vehicle may lose several miles per hour while going uphill in Cruise Control if the Cruise linkage is readjusted to avoid an unwanted 3-2 downshift.

2. CRUISE CONTROL VACUUM CONTROL VALVE - 1982-1983 MODELS

Use of an incorrect Cruise Control vacuum control valve on a 1982 V-6 or a 1982-1983 diesel equipped vehicle may result in damage to the Cruise ControUer. The GMWDD Parts Catalog, dated 1/83, Group 3.885, has incorrectly transposed the HT4100 vacuum control valve part number with that for diesel and V-6 vehicles.

The correct parts usage is as follows: Connector Diode Application Part Number Body Color In Valve? ------------ ----------- ---------- -------- 1982-1983 HT4100 1997597 Black Yes 1982-1983 Diesel 1997478 White or Blue No 1982 V-6 1997478 White or Blue No

The vacuum control valve used on HT4100 equipped vehicles contains a diode to prevent damage to the ECM. Some V-6 and diesel equipped vehicles may be wired such that if a vacuum control valve containing a diode is used, the diode will appear as a short circuit to the Cruise Controller.

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.