User guide

64 www.AutoEnginuity.com
GM:
Vehicle Preparation for OBD-II Drive Cycle
1. Cold Start. In order to be classified as a cold start the engine
coolant temperature must be below 122° F (50° C) and within
11° F (6° C) of the ambient air temperature at startup. Do not
leave the key on prior to the cold start or the heated oxygen sen-
sor diagnostic may not run.
2. Idle. The engine must be run for two and a half minutes with the
air conditioner on and rear defrost on.The more electrical load
you can apply the better. This will test the O2 heater, Passive
Air, Purge "No Flow", Misfire and if closed loop is achieved,
Fuel Trim.
3. Accelerate. Turn off the air conditioner and all the other loads
and apply half throttle until 55 mph (88 km/hr) is reached. Dur-
ing this time the Misfire, Fuel Trim, and Purge Flow diagnostics
will be performed.
4. Hold Steady Speed. Hold a steady speed of 55 mph (88 km/hr)
for 3 minutes. During this time the O2 response, air Intrusive,
EGR, Purge, Misfire, and Fuel Trim diagnostics will be per-
formed.
5. Decelerate. Let off the accelerator pedal. Do not shift, touch the
brake or clutch. It is important to let the vehicle coast along
gradually slowing down to 20 mph (32 km/hr). During this time
the EGR, Purge and Fuel Trim diagnostics will be performed.
6. Accelerate. Accelerate at 3/4 throttle until 55-60 mph (88-96
km/hr). This will perform the same diagnostics as in step 3.
7. Hold Steady Speed. Hold a steady speed of 55mph (88km/hr)
for five minutes. During this time, in addition to the diagnostics
performed in step 4, the catalyst monitor diagnostics will be per-
formed. If the catalyst is marginal or the battery has been dis-
connected, it may take 5 complete driving cycles to determine
the state of the catalyst.
8. Decelerate. This will perform the same diagnostics as in step 5.
Again, don't press the clutch or brakes or shift gears.