GM Enhanced (OBD II) Diagnostics
5 – 16 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
5
✓If an Error Message displays, make sure the OBD II connector is
securely attached, and the ignition key is on. Cycle the ignition key
to off for 10 seconds, then on. This may be required to reset the
computer. If required, select yes to try again. If the problem still
exists, refer to Error Messages on page 8-2.
Diagnostic Codes Menu
All items marked with “-” are covered either in section 3 or 4.
These items are not covered in this section.
❒Diagnostic Codes Menu
❒Read Codes
–Pending Codes
❒Erase Codes
– View Freeze Data
–Review Data
–Print Data
–Code Lookup
–Tool Setup
Read Codes
✓The Read Codes function retrieves DTCs from the vehicle’s
computer module(s). This function can be performed with the
KOEO or KOER. These codes cause the computer to illuminate
the malfunction indicator lamp (MIL) when an emission-related or
driveability fault occurs. The MIL is also known as the service
engine soon or check engine lamp.
✓The GM Enhanced reads DTC’s from the engine or powertrain
module (ENG), transmission module (TRANS), or transfer case
module (XFER).
✓Not all GM vehicles support DTC status. Some only use the Global
OBDII Read Codes command. For a description of these screens,
refer to the Global OBD II Diagnostics section of the manual.
•History Codes — Intermittent codes placed in the vehicle’s memory
when the trouble originally occurred, and will remain there even if
the trouble has been corrected. If no trouble after 50 engine
warm-up cycles, the DTC will be erased.
•Current Codes — Codes transmitted through the PCMs data
stream when a trouble condition is active and cannot be erased. The
problem must be repaired to remove the DTC.
•Intermittent Codes — Indicates the current code has been set at
least once but possibly not enough to cause a history code to be
stored.
IMPORTANT