Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Service manual — part 258
6E–62
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
On-Board Diagnostic (OBD II) System Check
(Cont'd)
Step
No
Yes
Value(s)
Action
12
Compare PCM data values displayed on the Tech 2 to
the typical engine scan data values.
Are the displayed values normal or close to the typical
values?
—
Go to
Symptom
Refer to
indicated
Component
System
Checks
13
1. Ignition “OFF”, disconnect the PCM.
2. Ignition “ON”, engine “OFF”.
3. Check the Class 2 data circuit for an open, short to
ground, or short to voltage. Also, check the DLC
ignition feed circuit for an open or short to ground
and the DLC ground circuit for an open.
4. If a problem is found, repair as necessary.
Was a problem found?
—
Go to
Step 2
Go to
Step 14
14
1. Attempt to reprogram the PCM. Refer to
Powertrain
Control Module (PCM) in On-Vehicle Service.
2. Attempt to display PCM data with the Tech 2.
Does the Tech 2 display PCM engine data?
—
Go to
Step 2
Go to
Step 15
15
Replace the PCM.
IMPORTANT: The replacement PCM must be
programmed. Refer to
ON-Vehicle Service in Power
Control Module and Sensors for procedures.
And also refer to latest Service Bulletin. Check to see
if the latest software is released or not. And then Down
Load the LATEST PROGRAMMED SOFTWARE to the
replacement PCM.
Is the action complete?
—
Go to
Step 2
—
6E–63
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
060R100063
Circuit Description
When air conditioning and blower fan are selected, and if
the system has a sufficient refrigerant charge, a 12-volt
signal is supplied to the A/C request input of the
powertrain control module (PCM). The A/C request
signal may be temporarily canceled during system
operation by the electronic thermostat in the evaporator
case. When the A/C request signal is received by the
PCM, the PCM supplies a ground from the compressor
clutch relay if the engine operating conditions are within
acceptable ranges. With the A/C compressor relay
energized, voltage is supplied to the compressor clutch
coil.
The PCM will enable the compressor clutch to engage
whenever A/C has been selected with the engine running,
unless any of the following conditions are present:
D
The throttle is greater than 90%.
D
The ignition voltage is below 10.5 volts.
D
The engine speed is greater than 4500 RPM for 5
seconds or 5400 RPM.
D
The engine coolant temperature (ECT) is greater
than 125
°
C (257
°
F).
D
The intake air temperature (IAT) is less than 5
°
C
(41
°
F).
D
The power steering pressure switch signals a high
pressure condition.
Diagnostic Aids
To diagnose an the intermittent fault, check for following
conditions:
D
Poor connection at the PCM–Inspect connections for
backed-out terminals, improper mating, broken locks,
improperly formed or damaged terminals, and poor
terminal-to-wire connection.
D
Damaged harness–Inspect the wiring harness for
damage. If the harness appears to OK, observe the
A/C clutch while moving connectors and wiring
harnesses related to the A/C. A sudden clutch
malfunction will indicate the source of the intermittent
fault.
6E–64
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Diagnosis
This chart should be used for diagnosing the electrical
portion of the A/C compressor clutch circuit. A Tech 2 will
be used in diagnosing the system. The Tech 2 has the
ability to read the A/C request input to the PCM. The
Tech 2 can display when the PCM has commanded the
A/C clutch “ON”. The Tech 2 should have the ability to
override the A/C request signal and energize the A/C
compressor relay.
Test Description
IMPORTANT:
Do not engage the A/C compressor
clutch with the engine running if an A/C mode is not
selected at the A/C control switch.
The numbers below refer to the step numbers on the
Diagnostic Chart:
3. This a test determine is the problem is with the
refrigerant system. If the switch is open, A/C
pressure gauges will be used to determine if the
pressure switch is faulty or if the system is partially
discharged or empty.
4. Although the normal complaint will be the A/C clutch
failing to engage, it is possible for a short circuit to
cause the clutch to run when A/C has not been
selected. This step is a test for that condition.
7. There is an extremely low probability that both relays
will fail at the same time, so the substitution process
is one way to check the A/C Thermostat relay. Use
a known good relay to do a substitution check.
A/C Clutch Control Circuit Diagnosis
Step
Action
Value(s)
Yes
No
1
Was the “On-Board Diagnostic (OBD) System Check”
performed?
—
Go to
Step 2
Go to
OBD
System
Check
2
Are any other DTCs stored?
—
Go to the
other DTC
chart(s) first
Go to
Step 3
3
1. Disconnect the electrical connector at the pressure
switch located on the receiver/drier.
2. Use an ohmmeter to check continuity across the
pressure switch.
Is the pressure switch open?
—
Go to Air
Conditioning
to diagnose
the cause of
the open
pressure
switch
Go to
Step 4
4
IMPORTANT: Before continuing with the diagnosis, the
following conditions must be met:
D
The intake air temperature must be greater than
15
°
C. (60
°
F).
D
The engine coolant temperature must be less
than 119
°
C (246
°
F).
1. A/C “OFF”.
2. Start the engine and idle for 1 minute.
3. Observe the A/C compressor.
Is the A/C compressor clutch engaged even though
A/C has not been requested?
—
Go to
Step 37
Go to
Step 5
5
1. Idle the engine.
2. A/C “ON”.
3. Blower “ON”.
4. Observe the A/C compressor.
Is the A/C compressor magnetic clutch engaged?
—
Refer to
Diagnostic
Aids
Go to
Step 6
6
1. Engine idling.
2. A/C “ON”.
3. Blower “ON”.
4. Observe the “A/C Request” display on the Tech 2.
(Refer to the Miscellaneous test)
Does the tool “A/C Request” display indicate “Yes”?
—
Go to
Step 26
Go to
Step 7
6E–65
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
(Cont'd)
Step
No
Yes
Value(s)
Action
7
Temporarily substitute the A/C compressor relay in
place of the A/C thermostat relay, then repeat Step 5.
Did the “A/C Request” display indicate “Yes”?
—
Go to
Step 8
Go to
Step 9
8
Replace the original A/C thermostat relay.
Is the action complete?
—
Verify repair
—
9
Does the blower operate?
—
Go to
Step 10
Go to
Step 11
10
Repair the blower.
Is the action complete?
—
Verify repair
—
11
Check for a faulty 10A A/C fuse in the underdash fuse
panel.
Was the 10A fuse OK?
—
Go to
Step 13
Go to
Step 12
12
Check for short circuit and make repairs if necessary.
Replace the 10A A/C fuse.
Is the action complete?
—
Verify repair
—
13
1. Remove the glove box to gain access to the A/C
thermostat.
2. Disconnect the thermostat connector.
3. Attach a fused jumper between ground and the
thermostat wire.
4. A/C “ON”.
5. Blower “ON”.
Dose A/C request indicate “YES” on the Tech 2?
—
Go to
Step 14
Go to
Step 17
14
1. Ignition “ON”.
2. Use a DVM to check voltage at the electronic A/C
thermostat.
Was voltage equal to the specified value?
B+
Go to
Step 17
Go to
Step 15
15
Check for open wire between the thermostat and the
A/C switch.
Was the wire open?
—
Go to
Step 16
Go to
Step 17
16
Repair the open wire between the thermostat and the
A/C switch.
Is the action complete?
—
Verify repair
—
17
Check for an open circuit between A/C thermostat relay
and PCM A/C request terminal (F45).
Was there an open circuit?
—
Go to
Step 18
Go to
Step 19
18
Repair the open circuit between the PCM and A/C
thermostat relay.
Is the action complete?
—
Verify repair
—
19
1. Ignition “ON”.
2. Use a DVM to check voltage at the A/C pressure
switch.
Was voltage equal to the specified value?
B+
Go to
Step 21
Go to
Step 20
20
Repair the open circuit between the 10A A/C fuse and
the pressure switch.
Is the action complete?
—
Verify repair
—
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