ENGINE CONTROLS 1F–17
DAEWOO M-150 BL2
DIAGNOSTIC INFORMATION AND PROCEDURES
SYSTEM DIAGNOSIS
DIAGNOSTIC AIDS
If an intermittent problem is evident, follow the guide-
lines below.
Preliminary Checks
Before using this section you should have already per-
formed the “Euro On-Board Diagnostic (EOBD) System
Check.”
Perform a thorough visual inspection. This inspection
can often lead to correcting a problem without further
checks and can save valuable time. Inspect for the fol-
lowing conditions:
Engine Control Module (ECM) grounds for being
clean, tight, and in their proper location.
Vacuum hoses for splits, kinks, collapsing and proper
connections as shown on the Vehicle Emission Con-
trol Information label. Inspect thoroughly for any type
of leak or restriction.
Air leaks at the throttle body mounting area and the
intake manifold sealing surfaces.
Ignition wires for cracks, hardness, proper routing,
and carbon tracking.
Wiring for proper connections.
Wiring for pinches or cuts.
Diagnostic Trouble Code Tables
Do not use the Diagnostic Trouble Code (DTC) tables to
try and correct an intermittent fault. The fault must be
present to locate the problem.
Incorrect use of the DTC tables may result in the unnec-
essary replacement of parts.
Faulty Electrical Connections or Wiring
Most intermittent problems are caused by faulty electri-
cal connections or wiring. Perform a careful inspection
of suspect circuits for the following:
Poor mating of the connector halves.
Terminals not fully seated in the connector body.
Improperly formed or damaged terminals. All connec-
tor terminals in a problem circuit should be carefullyinspected, reformed, or replaced to insure contact
tension.
Poor terminal-to-wire connection. This requires re-
moving the terminal from the connector body.
Road Test
If a visual inspection does not find the cause of the prob-
lem, the vehicle can be driven with a voltmeter or a scan
tool connected to a suspected circuit. An abnormal volt-
age or scan tool reading will indicate that the problem is
in that circuit.
If there are no wiring or connector problems found and a
DTC was stored for a circuit having a sensor, except for
DTC P0171 and DTC P0172, replace the sensor.
Intermittent Malfunction Indicator Lamp
(MIL)
An intermittent Malfunction Indicator Lamp(MIL) with no
DTC present may be caused by the following:
Improper installation of electrical options such as
lights, two way radios, sound, or security systems.
MIL driver wire intermittently shorted to ground.
Fuel System
Some intermittent driveability problems can be attrib-
uted to poor fuel quality. If a vehicle is occasionally run-
ning rough, stalling, or otherwise performing badly, ask
the customer about the following fuel buying habits:
Do they always buy from the same source? If so, fuel
quality problems can usually be discounted.
Do they buy their fuel from whichever fuel station that
is advertising the lowest price? If so, check the fuel
tank for signs of debris, water, or other contamina-
tion.
IDLE LEARN PROCEDURE
Whenever the battery cables, the Engine Control Mod-
ule (ECM), or the fuse is disconnected or replaced, the
following idle learn procedure must be performed:
1. Turn the ignition ON for 10 seconds.
2. Turn the ignition OFF for 10 seconds.
ENGINE CONTROLS 1F–281
DAEWOO M-150 BL2
INTERMITTENT
Definition: The problem may or may not illuminate the
Malfunction Indicator Lamp (MIL) or store a Diagnostic
Trouble Code (DTC).
Important: Do not use the Diagnostic Trouble Code
(DTC) tables for intermittent problems. A fault must bepresent in order to locate the problem. If a fault is inter-
mittent, use of Diagnostic Trouble Code tables may re-
sult in the replacement of good parts.
StepActionValue(s)YesNo
1
Were the Important Preliminary Checks performed?
–
Go to Step 2
Go to
“Important
Preliminary
Checks”
2
1. Perform a careful inspection of any suspect
circuits.
2. Inspect for poor mating of the connector halves,
or terminals not fully seated into the connector
body.
3. Inspect for improperly formed or damaged
terminals.
4. Inspect for poor terminal-to-wire connections.
This requires removing the terminal from the
connector body to inspect it.
Are any problems present?
–
Go to Step 3Go to Step 4
3Repair the electrical connections as needed.
Is the repair complete?–System OK–
4
Road test the vehicle with a voltmeter connected to
a suspected circuit or a scan tool connected to the
Data Link Connector (DLC).
Did the voltmeter or the scan tool indicate an
abnormal voltage or scan reading?
–
Go to Step 5Go to Step 6
5
Replace the sensor in the affected circuit, if a
Diagnostic Trouble Code (DTC) was stored for this
circuit (except for the DTCs P0171 and P0172).
Is the repair complete?
–
System OK
–
6Does an intermittent Malfunction Indicator Lamp
(MIL) or DTC occur?–Go to Step 7Go to Step 8
7
1. Check for a faulty relay, Engine Control Module
(ECM) driven solenoid, or switch.
2. Check for improper installation of electrical
devices, such as lights, two-way radios, electric
motors, etc.
3. Inspect the ignition control wires for proper
routing (away from ignition wires, ignition system
components, and the generator).
4. Check for a short-to-ground in the MIL circuit or
the DLC “test” terminal.
5. Inspect the ECM ground connections.
6. Correct or repair the affected circuits as needed.
Is the repair complete?
–
System OK
–
8
1. Check for a loss of DTC memory.
2. Disconnect the throttle position (TP) sensor.
3. Run the engine at idle until the MIL comes on.
4. Turn the ignition OFF.
Is DTC P0122 stored in memory?
–
Go to Step 10Go to Step 9
