Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 1997 GMC Yukon, 1997 GMC Suburban, 1997 GMC Pickup, 1997 GMC Cab & Chassis, and 1997 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
DTC could be caused by an IAC valve which is stopped and cannot respond to VCM, a throttle stop screw which has been tampered with, or a damaged throttle or linkage.
A slow, unstable or fast idle could be caused by a non-IAC valve system problem that cannot be overcome by IAC valve. See the TESTS W/O CODES article. Out of range control IAC scan tool counts will be greater than 60 if idle is too low and zero if idle is too high. Check for fuel system too lean and rich. Check throttle body bore for foreign material. IAC reset is done with scan tool miscellaneous functions mode.