Daewoo NUBIRA, User Manual

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1F – 28 I ENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSIS
SYSTEM DIAGNOSIS
DIAGNOSTIC AIDS
If an intermittent problem is evident, follow the guidelines
below.
Preliminary Checks
Before using this section you should have already per-
formed the ”On–Board Diagnostic 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 following con-
ditions:
S
Powertrain control module (PCM)/engine control
module (PCM/ECM) grounds for being clean, tight,
and in their proper location.
S
Vacuum hoses for splits, kinks, collapsing and prop-
er connections as shown on the Vehicle Emission
Control Information label. Inspect thoroughly for
any type of leak or restriction.
S
Air leaks at the throttle body mounting area and the
intake manifold sealing surfaces.
S
Ignition wires for cracks, hardness, proper routing,
and carbon tracking.
S
Wiring for proper connections.
S
Wiring for pinches or cuts.
Diagnostic Trouble Code Tables
Do not use the diagnostic trouble code (DTC) tables to try
to correct an intermittent fault. The fault must be present
to locate the problem.
Incorrect use of the DTC tables may result in the unneces-
sary replacement of parts.
Faulty Electrical Connections or Wiring
Most intermittent problems are caused by faulty electrical
connections or wiring. Perform a careful inspection of sus-
pect circuits for the following:
S
Poor mating of the connector halves.
S
Terminals not fully seated in the connector body.
S
Improperly formed or damaged terminals. All con-
nector terminals in a problem circuit should be care-
fully inspected, reformed, or replaced to insure con-
tact tension.
S
Poor terminal–to–wire connection. This requires
removing 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 voltage
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 Service Reminder Indicator (SRI) Lamp
An intermittent service reminder indicator (SRI) lamp with
no DTC present may be caused by the following:
S
Electrical system interference caused by a defec-
tive relay, PCM/ECM driven solenoid, or switch.
S
Improper installation of electrical options such as
lights, two–way radios, sound systems, or security
systems.
S
Ignition control wires should be routed away from
ignition wires, ignition system components, and the
generator.
S
Ignition secondary wires shorted to ground.
S
SRI lamp driver wire or diagnostic test terminal in-
termittently shorted to ground.
S
Intermittent lose of PCM/ECM ground connections.
Fuel System
Some intermittent driveability problems can be attributed
to poor fuel quality. If a vehicle is occasionally running
rough, stalling, or otherwise performing badly, ask the cus-
tomer about the following fuel buying habits:
S
Do they always buy from the same source? If so,
fuel quality problems can usually be discounted.
S
Do they buy their fuel from whichever fuel station
that is advertising the lowest price? If so, check the
fuel tank forsigns of debris, water, orotherconta-
mination.
IDLE LEARN PROCEDURE
Whenever the battery cables, the powetrain control mod-
ule (PCM)/engine control module (PCM/ECM), or the
PCM/ECM fuse is disconnected or replaced, the following
idle learn procedure must be performed:
1. Turn the ignition ON for 5 seconds.
2. Turn the ignition OFF for 5 seconds.
3. Turn the ignition ON for 5 seconds.
4. Start the engine in park/neutral.
5. Allow the engine run until the engine coolant is
above 85
°
C (185
°
F).
6. Turn the A/C ON for 10 seconds, if equipped.
7. Turn the A/C OFF for 10 seconds, if equipped.
8. If the vehicle is equipped with an automatic trans-
axle, apply the parking brake. While pressing the
brake pedal, place the transaxle in D (drive).
9. Turn the A/C ON for 10 seconds, if equipped.
10. Turn the A/C OFF for 10 seconds, if equipped.
11. Turn the ignition OFF. The idle learn procedure is
complete.