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GM Historic (OBD I) Diagnostics
5
A message confirming that the
Erase
Codes
command was successful dis-
plays. Press
to return to theGM
Function List.
Manual Erase Methods
Alternate Method 1:
1) Turn Ignition Key Off.
2) Locate Fuse Box and Remove ECM Fuse.
3) Wait 20 seconds.
4) Replace the Fuse.
Alternate Method 2:
1) Turn Ignition Key Off.
2) Remove Power from Scan Tool.
3) Disconnect Scan Tool from Vehicle.
4) Remove Negative (-) Battery Cable. Wait 30 seconds, then replace the
cable.
✓ The computer has a “learning” ability to compensate for minor variations
in engine operation. Whenever power is removed from the PCM, the com-
puter must “relearn” various functions. Vehicle performance may be
noticeably different until this is accomplished. This is a temporary situation
and is normal. The “learning” process takes place during warm engine
driving.
View Data
The
View Data
function allows the user to view the vehicle Parameter Identi-
fication Data (PIDs) in real time. As the PCM monitors PIDs, they are simulta-
neously transmitted to the scan tool. The PIDs are continuously updated at the
PCM’s rate.
In addition to reading codes,
View Data
is the most useful diagnostic function
for isolating the cause of a vehicle operation problem. Viewing data is also used
for observing sensor data and the ON/OFF state of switches, solenoids, and
relays.
View Data
can be performed with the ignition key On-Engine Off or Running.
Never operate the tool while driving. Have another person
assist with the operation of the tool.
Select
View Data
from the GM Func-
tion List and press
. If a Select
Group screen does not appear, skip the
Multiple Group section and continue.
Multiple Group Vehicles
Some vehicles display a Select Group
screen for viewing data. In these cases,
only one group of data can be viewed at
a time.
!
WARNING
!
WARNING