Engine Controls Visual Inspection; Intermittent Problems - EDI TSG-416 Service Manual

Visual Inspection
Perform a careful visual and physical engine
inspection before performing any diagnostic
procedure. Perform all necessary repairs before
proceeding with additional diagnosis, this can
often lead to repairing a problem without
performing unnecessary steps. Use the following
guidelines when performing a visual/physical
inspection check:

Inspect engine for modifications or
aftermarket equipment that can
contribute to the symptom; verify that all
electrical and mechanical loads or
accessory equipment is "OFF" or
disconnected before performing
diagnosis.

Inspect engine fluids for correct levels
and evidence of leaks.

Inspect vacuum hoses for damage,
leaks, cracks, kinks and improper
routing, inspect intake manifold sealing
surface for a possible vacuum leak.

Inspect PCV valve for proper installation
and operation.

Inspect all wires and harnesses for
proper connections and routing; bent or
broken connector pins; burned, chafed,
or pinched wires; and corrosion. Verify
that harness grounds are clean and
tight.

Inspect GCP, sensors and actuators for
physical damage.

Inspect GCP grounds for cleanliness,
tightness, and proper location.

Inspect fuel system for adequate fuel
level, and fuel quality (concerns such as
proper octane, contamination,
winter/summer blend).

Inspect intake air system and air filter for
restrictions.

Inspect battery condition and starter
current draw.
If no evidence of a problem is found after visual
inspection has been performed, proceed to
"Diagnostic System Check"
TSG‐416 Engine Controls

Intermittent Problems

NOTE: An intermittent problem may or may not
turn on the MIL or store a DTC. Do not use the
DTC charts for intermittent problems. The fault
must be present to locate the problem.
NOTE: Most intermittent problems are caused
by faulty electrical connections or wiring.
Perform a careful visual inspection for the
following conditions:





Operate the engine with accessories "OFF" and
a suitable multimeter connected to the
suspected circuit. An abnormal voltage when the
malfunction occurs is a good indication that
there is a fault in the circuit being monitored.
To check GCP for loss of diagnostic code
memory, disconnect the MAP sensor connector
and idle the engine until the MIL illuminates.
Perform MIL DTC retrieval procedure. DTC
should be stored and kept in memory when the
ignition is turned "OFF". If not, the GCP is faulty.
When this test is completed, make sure that you
clear the DTC from memory. An intermittent
MIL with no stored DTC may be caused by the
following:



08 ‐ 35
Poor mating of the connector halves or
a terminal not fully seated in the
connector (backed out).
Improperly formed or damaged
terminals
Improper contact tension. All connector
terminals in the problem circuit should
be carefully checked.
Poor terminal-to-wire connections. This
requires removing the terminal from the
connector body to check.
Improperly installed aftermarket
equipment or accessories.
Ignition coil shorted to ground and
arcing at plugs.
MIL circuit to GCP shorted to ground.
Poor GCP grounds.