Jeep Cherokee 2000 Service Manual - page 1260
RELAYS—OPERATION/TESTING
The following description of operation and
tests apply only to the ASD and other relays.
The terminals on the bottom of each relay are num-
bered (Fig. 19).
OPERATION
•
Terminal number 30 is connected to battery volt-
age. For both the ASD and other relays, terminal 30
is connected to battery voltage at all times.
•
The ECM grounds the coil side of the relay
through terminal number 85.
•
Terminal number 86 supplies voltage to the coil
side of the relay.
•
When the PCM de-energizes the ASD and other
relays, terminal number 87A connects to terminal 30.
This is the Off position. In the off position, voltage is
not supplied to the rest of the circuit. Terminal 87A
is the center terminal on the relay.
•
When the ECM energizes the ASD and other
relays, terminal 87 connects to terminal 30. This is
the On position. Terminal 87 supplies voltage to the
rest of the circuit.
TESTING
The following procedure applies to the ASD and
other relays.
(1) Remove relay from connector before testing.
(2) With the relay removed from the vehicle, use
an ohmmeter to check the resistance between termi-
nals 85 and 86. The resistance should be between 75
6
5 ohms.
(3) Connect the ohmmeter between terminals 30
and 87A. The ohmmeter should show continuity
between terminals 30 and 87A.
(4) Connect the ohmmeter between terminals 87
and 30. The ohmmeter should not show continuity at
this time.
(5) Connect one end of a jumper wire (16 gauge or
smaller) to relay terminal 85. Connect the other end
of the jumper wire to the ground side of a 12 volt
power source.
(6) Connect one end of another jumper wire (16
gauge or smaller) to the power side of the 12 volt
power source. Do not attach the other end of the
jumper wire to the relay at this time.
WARNING: DO NOT ALLOW OHMMETER TO CON-
TACT TERMINALS 85 OR 86 DURING THIS TEST.
(7) Attach the other end of the jumper wire to
relay terminal 86. This activates the relay. The ohm-
meter should now show continuity between relay ter-
minals 87 and 30. The ohmmeter should not show
continuity between relay terminals 87A and 30.
(8) Disconnect jumper wires.
(9) Replace the relay if it did not pass the continu-
ity and resistance tests. If the relay passed the tests,
it operates properly. Check the remainder of the ASD
and other relay circuits. Refer to group 8W, Wiring
Diagrams.
BOOST / PRESSURE SENSOR
If the boost pressure sensor fails, the PCM records
a DTC into memory and continues to operate the
Fig. 19 Glow Plug Relay Location
1 – MOUNTING BOLT
2 – GLOW PLUG RELAY
3 – ELECTRICAL CONNECTOR
Fig. 20 Boost Pressure Sensor Location
1 – BOOST PRESSURE SENSOR HARNESS CONNECTOR
2 – BOOST PRESSURE SENSOR
14 - 34
FUEL SYSTEM—2.5L DIESEL ENGINE
XJ
DIAGNOSIS AND TESTING (Continued)