Cruise Control - Information Update

Bulletin No. T 83-64
File In Group 9
Number 16
Date April '83

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 60~ 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 Controller. 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.