SCAN TOOL WORKSHEET ALL ECM EQUIPPED VEHICLES

VEHICLES AFFECTED: 1985 All Vehicles

The SCAN TOOL WORKSHEET was designed to help organize the data available when diagnosing an E.C.M. equipped vehicle. The form, GMP514, is available at no charge from Dyment Limited and comes in a pad of 50 sheets.

The column, 'Key On, Engine Off' should be completed first. The 'Tape Counter' row is only used to log tape footage numbers when the Diagnostic Data Recorder is also being used. Any abnormal conditions detected should be repaired before proceeding to the next column.

Note that NAP or VAC readings will vary dlightly due to atmospheric pressure changes. (weather changes or geographical location).

The 'Idle, Closed Loop' column should be completed after the engine has been run long enough to heat the oxygen sensor to operating temperature. On Canadian emission equipped vehicles, the Oxygen Sensor voltage will remain at approximately 460 MV. and Loop Status will be 'Open'.

The two remaining columns are provided for 30 MPH or 60 MPH data if the nature of the customer's concern dictates a road test. Local speed limits may require the 60 MPH test to be done at 50 MPH. It is important for purposes of repeatibility that road load values be recorded. Road load is defined as driving on level road in the highest gear practical with only enough throttle to maintain vehicle speed. These operating conditions are critical as only small changes of throttle opening or engine load will cause major changes in the data.

Following are some important points to remember when using a scan tool for diagnosis:

Always confirm the customer's concern without the scan tool installed as it may alter ignition timing and fuel control to the point of eliminating or inducing a driveability problem.

Ensure the correct engine/emission system has been selected.

Engine System

3.0, 3.8, 3.8T bu PFI 1.8T P18 PFI 1.8, 2.5 PO EFI 2.0 CH EFI 2.8, 5.0, 5.7 CH PFI 2.8 Fiero P28 PFI

To help you become familiar with the scan tool readings, attached are some sample sheets completed from known good vehicles. These sheets are intended only as an aid in understanding scan readings and are not to be considered as vehicle specifications for repair decisions.

You are strongly urged to complete scan sheets when road testing known good cars (P.D.I., rattle/squeak repair, wheel balance repair, etc.) to become more familiar with the M.P.S.I. Multi-Scanner J-35255 made essential in 1985. This personal library will help you quickly identify out of line conditions when diagnosing a customer's vehicle.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.