5B.13
Section 5B
EFI Fuel System
5B
a. If there is no continuity displayed in either of
the tests, check the harness circuit for breaks
or damage, and the connections for poor
contact, moisture, or corrosion. If no
continuity was found in the first test, also
check for a poor/broken ground path back
through the exhaust system, engine, and
mounting (sensor is grounded through its
shell).
b. If continuity is indicated, go to step 6.
6. With the key switch in the ‘‘on/run’’ position,
using a high impedance voltmeter, check the
voltage from the wiring harness oxygen sensor
connector to the engine ground location. Look for
a steady voltage from
350-550 mv (0.35-0.55 v)
.
a. If voltage reading is not as specified, move the
black voltmeter lead to the negative post of
the battery, to be certain of a good ground. If
the voltage is still not correct, the ECU is
probably bad.
b. If voltage readings are correct, clear the fault
codes and run the engine to check if any fault
codes reappear.
To Replace Oxygen Sensor
1. Disconnect the oxygen sensor connector from
wiring harness.
2. Loosen and remove the oxygen sensor from the
exhaust manifold/muffler assembly.
3. Apply anti-seize compound sparingly to threads
of new oxygen sensor, if none already exists.
DO
NOT
get any on the tip as it will contaminate the
sensor. Install sensor and torque to
50-60 N·m
(37-44 ft. lb.)
.
4. Reconnect the lead to wiring harness connector.
Make sure it can not contact hot surfaces, moving
parts, etc.
5. Test run the engine.
Electrical Relay
Figure 5B-13. Electrical Relay.
General
The electrical relay is used to supply power to the
injectors, coils, and fuel pump. When the key switch is
turned “on” and all safety switch requirements met,
the relay provides 12 volts to the fuel pump circuit,
injectors, and ignition coils. The fuel pump circuit is
continuously grounded, so the pump is immediately
activated and pressurizes the system. Activation of the
ignition coils and injectors is controlled by the ECU,
which grounds their respective circuits at the proper
times.
Service
A malfunctioning relay can result in starting or
operating difficulties. The relay and related wiring can
be tested as follows:
1. Disconnect the relay connector plug from the
relay.
2. Connect black lead of VOA meter to a chassis
ground location. Connect red lead to the #86
terminal in relay connector (see Figure 5B-14). Set
meter to test resistance (Rx1). Turn ignition
switch from
“off”
to
“on”
. Meter should indicate
continuity (ground circuit is completed) for 1 to 3
seconds. Turn key switch back off.
Содержание COMMAND CH18
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