You need to disconnect the EST wire tan and black wire-see below info
July, 13, 2010 AT 3:53 PM
V6 IGNITION TIMING 1. Set parking brake, block drive wheels and place transmission in Neutral or Park. Warm engine to normal operating temperature. Turn A/C off (if equipped). Ensure Malfunction Indicator Light (MIL) is off. 2. Disconnect Tan/Black Electronic Spark Timing (EST) by-pass connector wire. DO NOT disconnect 4-wire connector at distributor. 3. On models where engine computer is located underhood, on right fenderwell, by-pass connector which is a single Tan/Black wire, breaks out of wiring harness near engine computer harness connectors. 4. On models where engine computer is located in passenger compartment under right side of instrument panel, by-pass connector which is a single Tan/Black wire and breaks out of wiring harness where heater box and carpet meet on passenger side floor. Pull back carpet to expose single Tan/Black wire and connector on outside of control module harness. 5. On all models, connect timing light to No. 1 spark plug wire. Check timing and adjust if necessary. See V6 IGNITION TIMING table. Reconnect EST by-pass connector, and clear ECM trouble code. NOTE: The location of the EST by-pass connector has been updated per General Motors Service Manual Update number 41-65-41, dated January 4, 1995.
Timing is 0 degrees at idle, both auto and manual trans. Soory Razz! But this IS clearer!