GM Service Manual Online
For 1990-2009 cars only

Internal Mode Switch (IMS)

IMS Circuits/Parameter

Selector Position

Park

Reverse

Neutral

Drive

Manual

Direction Switch Operating Conditions: Ignition ON, range selector in appropriate gear

Direction IMS D1

HIGH

HIGH

LOW

LOW

LOW

Direction IMS D2

LOW

LOW

HIGH

HIGH

HIGH

Direction IMS R1

HIGH

LOW

LOW

HIGH

HIGH

Direction IMS R2

LOW

HIGH

HIGH

LOW

LOW

Direction IMS Start

LOW

HIGH

LOW

HIGH

HIGH

Range Switch Operating Conditions: Ignition ON, range selector in appropriate gear

IMS A

LOW

LOW

HI

HI

HI

IMS B

HI

LOW

LOW

LOW

HI

IMS C

HI

HI

HI

LOW

LOW

IMS P

LOW

HI

LOW

HI

LOW

Always HIGH status: Open/short to voltage condition

Always LOW status: Short to ground condition

Every status HIGH for either switch indicates an open ground circuit or connector for that portion of the IMS.