ENGINE CONTROLS 1F–9
DAEWOO M-150 BL2
appropriate wiring diagram. Refer to “ECM Wiring Dia-
grams” in this Section.
9591
Terminal 49GroundOpen
STRATEGY-BASED DIAGNOSTICS
Strategy-Based Diagnostics
The strategy-based diagnostic is a uniform approach to
repair all Electrical/Electronic (E/E) systems. The diag-
nostic flow can always be used to resolve an E/E system
problem and is a starting point when repairs are neces-
sary. The following steps will instruct the technician on
how to proceed with a diagnosis:
Verify the customer complaint. To verify the customer
complaint, the technician should know the normal op-
eration of the system.
Perform preliminary checks as follows:
Conduct a thorough visual inspection.
Review the service history.
Detect unusual sounds or odors.
Gather Diagnostic Trouble Code (DTC) information to
achieve an effective repair.
Check bulletins and other service information. This
includes videos, newsletters, etc.
Refer to service information (manual) system
check(s).
Refer to service diagnostics.
No Trouble Found
This condition exists when the vehicle is found to oper-
ate normally. The condition described by the customer
may be normal. Verify the customer complaint against
another vehicle that is operating normally. The condition
may be intermittent. Verify the complaint under the con-
ditions described by the customer before releasing the
vehicle.
Re-examine the complaints.
When the complaints cannot be successfully found or
isolated, a re-evaluation is necessary. The complaint
should be re-verified and could be intermittent as de-
fined in “intermittents,” or could be normal.
After isolating the cause, the repairs should be made.
Validate for proper operation and verify that the symp-
tom has been corrected. This may involve road testing
or other methods to verify that the complaint has re-
solved under following conditions:
Conditions noted by the customer.
If a DTC was diagnosed, verify the repair be duplicat-
ing conditions present when the DTC was set as
noted in Failure Records or Freeze Frame data.
Verifying Vehicle Repair
Verification of the vehicle repair will be more compre-
hensive for vehicles with Euro On-Board Diagnostic
(EOBD) system diagnostics. Following a repair, the
technician should perform the following steps:
Important: Follow the steps below when you verify re-
pairs on EOBD systems. Failure to follow these steps
could result in unnecessary repairs.
Review and record the Failure Records and the
Freeze Frame data for the DTC which has been diag-
nosed (Freeze Fame data will only be stored for an A,
B and E type diagnostic and only if the Malfunction
Indicator Lamp has been requested).
Clear the DTC(s).
Operate the vehicle within conditions noted in the
Failure Records and Freeze Frame data.
Monitor the DTC status information for the specific
DTC which has been diagnosed until the diagnostic
test associated with that DTC runs.
EOBD SERVICEABILITY ISSUES
Based on the knowledge gained from Euro On-Board
Diagnostic (OBD) experience in the 1994 and 1995
model years in United Status, this list of non-vehicle
faults that could affect the performance of the Euro On-
Board Diagnostic (EOBD) system has been compiled.
These non-vehicle faults vary from environmental condi-
tions to the quality of fuel used. With the introduction of
EOBD across the entire passenger car, illumination of
the Malfunction Indicator Lamp (MIL) due to a non-ve-
hicle fault could lead to misdiagnosis of the vehicle, in-
creased warranty expense and customer
dissatisfaction. The following list of non-vehicle faults
does not include every possible fault and may not apply
equally to all product lines.
Fuel Quality
Fuel quality is not a new issue for the automotive indus-
try, but its potential for turning on the MIL with EOBD
systems is new.
Fuel additives such as “dry gas” and “octane enhancers”
may affect the performance of the fuel. If this results in
an incomplete combustion or a partial burn, it will set
Diagnostic Trouble Code (DTC) P0300. The Reed Vapor
Pressure of the fuel can also create problems in the fuel
system, especially during the spring and fall months
when severe ambient temperature swings occur. A high
Reed Vapor Pressure could show up as a Fuel Trim
DTC due to excessive canister loading.
Using fuel with the wrong octane rating for your vehicle
may cause driveability problems. Many of the major fuel
companies advertise that using “premium” gasoline will
improve the performance of your vehicle. Most premium
