relay ISUZU TROOPER 1998 Service Owners Manual

6E±33 ENGINE DRIVEABILITY AND EMISSIONS
Undercarriage Component Locator Table (Manual Transmission)
Number
NameLocation
1Fuel Pump AssemblyInstalled in the top of the fuel tank
2Fuel Gauge UnitInstalled in the front edge of the right frame
rail, ahead of the rear axle
3Fuel FilterLocated along the inside of the right frame rail,
ahead of the rear axle
4Vehicle Speed Sensor (VSS)2WD: Protrudes from the transmission
housing, just ahead of the propeller shaft.
4WD: Protrudes from the rear output shaft
housing of the transfer case.
5Heated Oxygen Sensor (Bank 1, HO2S 1)Threaded into the exhaust pipe ahead of the
right-hand catalytic converter
6Heated Oxygen Sensor (Bank 2, HO2S 1)Threaded into the exhaust pipe ahead of the
left-hand catalytic converter
Fuse and Relay Panel (Underhood Electrical Center)
TS23336

6E±39 ENGINE DRIVEABILITY AND EMISSIONS
The data displayed on the other Tech 2 will appear the
same, with some exceptions. Some Tech 2s will only be
able to display certain vehicle parameters as values that
are a coded representation of the true or actual value. For
more information on this system of coding, refer to
Decimal/Binary/Hexadecimal Conversions. On this
vehicle Tech 2 displays the actual values for vehicle
parameters. It will not be necessary to perform any
conversions from coded values to actual values.
On-Board Diagnostic (OBD)
On-Board Diagnostic Tests
A diagnostic test is a series of steps, the result of which is
a pass or fail reported to the diagnostic executive. When
a diagnostic test reports a pass result, the diagnostic
executive records the following data:

The diagnostic test has been completed since the last
ignition cycle.

The diagnostic test has passed during the current
ignition cycle.

The fault identified by the diagnostic test is not
currently active.
When a diagnostic test reports a fail result, the diagnostic
executive records the following data:

The diagnostic test has been completed since the last
ignition cycle.

The fault identified by the diagnostic test is currently
active.

The fault has been active during this ignition cycle.

The operating conditions at the time of the failure.
Remember, a fuel trim DTC may be triggered by a list of
vehicle faults. Make use of all information available (other
DTCs stored, rich or lean condition, etc.) when
diagnosing a fuel trim fault.
Comprehensive Component Monitor
Diagnostic Operation
Input Components:
Input components are monitored for circuit continuity and
out-of-range values. This includes rationality checking.
Rationality checking refers to indicating a fault when the
signal from a sensor does not seem reasonable, i.e.
Throttle Position (TP) sensor that indicates high throttle
position at low engine loads or MAP voltage. Input
components may include, but are not limited to the
following sensors:

Vehicle Speed Sensor (VSS)

Crankshaft Position (CKP) sensor

Knock Sensor (KS)

Throttle Position (TP) sensor

Engine Coolant Temperature (ECT) sensor

Camshaft Position (CMP) sensor

Manifold Absolute Pressure (MAP) sensor

Mass Air Flow (MAF) sensorIn addition to the circuit continuity and rationality check,
the ECT sensor is monitored for its ability to achieve a
steady state temperature to enable closed loop fuel
control.
Output Components:
Output components are diagnosed for proper response to
control module commands. Components where
functional monitoring is not feasible will be monitored for
circuit continuity and out-of-range values if applicable.
Output components to be monitored include, but are not
limited to, the following circuits:

Idle Air Control (IAC) Motor

Electronic Transmission controls

A/C relays

Cooling fan relay

VSS output

MIL control

Cruise control inhibit
Refer to PCM and Sensors in General Descriptions.
Passive and Active Diagnostic Tests
A passive test is a diagnostic test which simply monitors a
vehicle system or component. Conversely, an active test,
actually takes some sort of action when performing
diagnostic functions, often in response to a failed passive
test. For example, the EGR diagnostic active test will
force the EGR valve open during closed throttle decel
and/or force the EGR valve closed during a steady state.
Either action should result in a change in manifold
pressure.
Intrusive Diagnostic Tests
This is any on-board test run by the Diagnostic
Management System which may have an effect on
vehicle performance or emission levels.
Warm-Up Cycle
A warm-up cycle means that engine at temperature must
reach a minimum of 70
C (160
F) and rise at least 22
C
(40
F) over the course of a trip.
Freeze Frame
Freeze Frame is an element of the Diagnostic
Management System which stores various vehicle
information at the moment an emissions-related fault is
stored in memory and when the MIL is commanded on.
These data can help to identify the cause of a fault. Refer
to
Storing And Erasing Freeze Fame Data for more
detailed information.
Failure Records
Failure Records data is an enhancement of the OBD
Freeze Frame feature. Failure Records store the same
vehicle information as does Freeze Frame, but it will store
that information for any fault which is stored in on-board
memory, while Freeze Frame stores information only for
emission-related faults that command the MIL on.

6E±54
ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
D06RW085
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. The electronic thermostat may intermittently
remove the control circuit ground for the A/C thermostat
relay to prevent the evaporator from forming ice. 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:
The throttle is greater than 90%.

The ignition voltage is below 10.5 volts.

The engine speed is greater than 4500 RPM for 5
seconds or 5400 RPM.

The engine coolant temperature (ECT) is greater than
125
C (257
F).

The intake air temperature (IAT) is less than 5
C
(41
F).

The power steering pressure switch signals a cramped
position.
Diagnostic Aids
To diagnose an the intermittent fault, check for the
following conditions:

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.

6E±55 ENGINE DRIVEABILITY AND EMISSIONS

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.
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 ªON.º 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.
9. The blower system furnishes a ground for the A/C
control circuit, and it also shares a power source
through the Heater and A/C Relay. The blower
must be ªONº in order to test the A/C system.
A/C Clutch Control Circuit Diagnosis

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Are any other DTCs stored?
Ð
Go to the
other DTC
chart(s) first
Go to Step 3
31. 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?
Ð
Go to Air
Conditioning
to diagnose
the cause of
the open
pressure
switch
Go to Step 4
4IMPORTANT:Before continuing with the diagnosis, the
following conditions must be met:

The intake air temperature must be greater than
15
C. (60
F).

The engine coolant temperature must be less
than 119
C (246
F).
1. A/C ªOFF.º
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?
ÐGo to Step 45Go to Step 5
51. Idle the engine.
2. A/C ªONº.
3. Blower ªONº.
4. Observe the A/C compressor.
Is the A/C compressor magnetic clutch engaged?
Ð
Refer to
Diagnostic
Aids
Go to Step 6

6E±56
ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis

 
StepNo Ye s Value(s) Action
61. Engine idling.
2. A/C ªONº.
3. Blower ªONº.
4. Observe the ªA/C Requestº display on the Tech 2.
Does the tool ªA/C Requestº display indicate ªYes?º
ÐGo to Step 34Go to Step 7
7Temporarily substitute the A/C compressor relay in
place of the A/C thermostat relay, then repeat Step 5.
Did the ªA/C Requestº display indicate ªYes?º
ÐGo to Step 8Go to Step 9
8Replace the original A/C thermostat relay.
Is the action complete?
ÐVerify repairÐ
9Dose the blower operate?ÐGo to Step 10Go to Step 11
10Repair the blower.
Is the action complete?
ÐVerify repairÐ
11Check for a faulty 10a A/C fuse in the underdash fuse
panel.
Was the 10A fuse OK?
ÐGo to Step 13Go to Step 12
12Check for short circuit and make repairs if necessary.
Replace the 10A A/C fuse.
Is the action complete?
ÐVerify repairÐ
131. Ignition ªON.º
2. Use a DVM to check voltage at the positive A/C
switch wire (BRN).
Was voltage equal to the specified value?
+BGo to Step 15Go to Step 14
14Repair the open wire (BRN) between the A/C switch
and the A/C fuse.
Is the action complete?
ÐVerify repairÐ
151. 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
PNK/GRN wire at the thermostat.
4. A/C ªON.º
5. Blower ªON.º
Dose A/C request indicate ªYESº on the Tech 2?
ÐGo to Step 16Go to Step 23
161. Ignition ªON.º
2. Use a DVM to check voltage at the electronic A/C
thermostat.
Was voltage equal to the specified value?
+BGo to Step 20Go to Step 17
17Check for an open (LT GRN) between the thermostat
and the A/C switch.
Was the wire open?
ÐGo to Step 18Go to Step 19
18Repair the open wire (LT GRN) between the thermostat
and the A/C switch.
Is the action complete?
ÐVerify repairÐ

6E±57 ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis

 
StepNo Ye s Value(s) Action
19Replace the A/C switch.
Is the action complete?
ÐVerify repairÐ
20Use an ohmmeter to check continuity between the
electronic A/C thermostat and the blower switch.
Was there an open circuit?
ÐGo to Step 21Go to Step 22
21Repair the open wire (GRN/YEL) between the
thermostat and the blower switch.
Is the action complete?
ÐVerify repairÐ
22Replace the electronic A/C thermostat.
Is the an action complete?
ÐVerify repairÐ
23Check for an open circuit between A/C thermostat relay
and PCM A/C request terminal (E-15).
Was there an open circuit?
ÐGo to Step 24Go to Step 25
24Repair the open circuit between the PCM and A/C
thermostat relay.
Is the action complete?
ÐVerify repairÐ
25Check for an open circuit between the A/C switch (LT
GRN) and the A/C thermostat relay (LT GRN).
Was there an open circuit?
ÐGo to Step 26Go to Step 27
26Repair the open circuit between the A/C switch and the
A/C thermostat relay.
Is the action complete?
ÐVerify repairÐ
271. Ignition ªON.º
2. Use a DVM to check voltage at the A/C pressure
switch (BRN).
Was voltage equal to the specified value?
+BGo to Step 29Go to Step 28
28Repair the open circuit between the 10A A/C fuse and
the pressure switch.
Is the action complete?
ÐVerify repairÐ
29Use an ohmmeter to check continuity between the
pressure switch (GRN/WHT) and the A/C thermostat
relay (GRN/WHT).
Was the circuit open?
ÐGo to Step 30Go to Step 31
30Repair the open circuit between the pressure switch
and the A/C thermostat relay.
Is the action complete?
ÐVerify repairÐ
31Check for damaged pin or terminal at E-15 of the PCM.
Was a damaged pin or terminal found?
ÐGo to Step 32Go to Step 33
32Repair the damaged pin or terminal.
Is the action complete?
ÐVerify repairÐ
33Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?ÐVerify repairÐ

6E±58
ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis

 
StepNo Ye s Value(s) Action
341. Remove the A/C compressor relay.
2. Ignition ªON.º
3. Use a DVM to check voltage at both of the BRN
wires at the A/C compressor relay socket.
Is the voltage equal to the specified value?
+BGo to Step 36Go to Step 35
35Repair the faulty BRN wire between the A/C fuse and
the A/C compressor relay .
Is the action complete?
ÐVerify repairÐ
361. A/C compressor relay removed.
2. Engine idling.
3. A/C ªON.º
4. Blower ªON.º
5. Use a DVM to measure voltage between the
GRN/BLK wire at the A/C compressor relay socket
and battery+.
Did the DVM indicate the specified value?
+BGo to Step 40Go to Step 37
37Check for an open GRN/BLK wire between PCM
terminal B-14 and the A/C compressor relay.
Was the wire open?
ÐGo to Step 38Go to Step 39
38Repair the open GRN/BLK wire between the PCM and
the A/C compressor relay.
Is the action complete?
ÐVerify repairÐ
39Check for a damaged pin or terminal at B-14 of the
PCM.
Was a damaged pin or a terminal found?
ÐGo to Step 32Go to Step 33
401. A/C compressor relay removed.
2. Connect a fused jumper at the A/C compressor
relay socket between either BRN wire and the
BRN/YEL wire.
3. Engine idling.
4. A/C ªON.º
5. Blower ªON.º
Did the compressor magnetic clutch engage?
ÐGo to Step 41Go to Step 42
41Repair the A/C compressor relay.
Is the action complete?
ÐVerify repairÐ
42Check for an open circuit between the A/C compressor
relay and the A/C clutch.
Was an open circuit found?
ÐGo to Step 43Go to Step 44
43Repair the open circuit between the compressor Clutch
and the A/C compressor relay.
Is the action complete?
ÐVerify repairÐ
44Service the compressor clutch or replace the
compressor due to a faulty internal overheat switch.
Is the action complete?
ÐVerify repairÐ

6E±59 ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis

 
StepNo Ye s Value(s) Action
451. Remove the A/C compressor relay.
2. Idle the engine.
Is the compressor clutch still engaged when A/C is not
selected?
ÐGo to Step 46Go to Step 47
46Repair the short to voltage between the A/C clutch and
A/C compressor relay.
Is the action complete?
ÐVerify repairÐ
471. Reinstall the A/C compressor relay.
2. Remove the A/C thermostat relay.
3. Engine idling.
Is the compressor clutch still engaged when A/C is not
selected?
ÐGo to Step 48Go to Step 50
48Use a DVM to check for a short to ground between the
A/C compressor relay and B-14 of the PCM.
Was a short detected?
ÐGo to Step 49Go to Step 33
49Repair the short to ground between the PCM and A/C
compressor relay.
Is the action complete?
ÐVerify repairÐ
50Repair the short to ground between the A/C thermostat
relay and the electronic thermostat.
Is the action complete?
ÐVerify repairÐ

6E±65 ENGINE DRIVEABILITY AND EMISSIONS
Knock Sensor Diagnosis
The Tech 2 has two data displays available for diagnosing
the knock sensor (KS) system. The two displays are
described as follows:

ªKnock Retardº indicates the number of degrees that
the spark timing is being retarded due to a knock
condition.

ªKS Noise Channelº indicates the current voltage level
being monitored on the noise channel.
DTCs P0325 and P0327 are designed to diagnose the KS
module, the knock sensor, and the related wiring. The
problems encountered with the KS system should set a
DTC. However, if no DTC was set but the KS system is
suspect because of a detonation complaint, refer to
Detonation/Spark Knock in Symptoms.
Powertrain Control Module (PCM)
Diagnosis
To read and clear diagnostic trouble codes, use a Tech 2.
IMPORTANT:Use of a Tech 2 is recommended to clear
diagnostic trouble codes from the PCM memory.
Diagnostic trouble codes can also be cleared by turning
the ignition ªOFFº and disconnecting the battery power
from the PCM for 30 seconds. Turning off the ignition and
disconnecting the battery power from the PCM will cause
all diagnostic information in the PCM memory to be
cleared. Therefore, all the diagnostic tests will have to be
re-run.
Since the PCM can have a failure which may affect only
one circuit, following the diagnostic procedures in this
section will determine which circuit has a problem and
where it is.
If a diagnostic chart indicates that the PCM connections
or the PCM is the cause of a problem, and the PCM is
replaced, but this does not correct the problem, one of the
following may be the reason:

There is a problem with the PCM terminal connections.
The terminals may have to be removed from the
connector in order to check them properly.

The problem is intermittent. This means that the
problem is not present at the time the system is being
checked. In this case, refer to the
Symptoms portion of
the manual and make a careful physical inspection of
all component and wiring associated with the affected
system.

There is a shorted solenoid, relay coil, or harness.
Solenoids and relays are turned ªONº and ªOFFº by the
PCM using internal electronic switches called drivers.
A shorted solenoid, relay coil, or harness will not
damage the PCM but will cause the solenoid or relay to
be inoperative.
Multiple PCM Information Sensor
DTCS Set
Circuit Description
The powertrain control module (PCM) monitors various
sensors to determine the engine operating conditions.
The PCM controls fuel delivery, spark advance,
transmission operation, and emission control device
operation based on the sensor inputs.The PCM provides a sensor ground to all of the sensors.
The PCM applies 5 volts through a pull-up resistor, and
determines the status of the following sensors by
monitoring the voltage present between the 5-volt supply
and the resistor:

The engine coolant temperature (ETC) sensor

The intake air temperature (IAT) sensor

The transmission fluid temperature (TFT) sensor
The PCM provides the following sensors with a 5-volt
reference and a sensor ground signal:

The exhaust gas recirculating (EGR) pintle position
sensor

The throttle position (TP) sensor

The manifold absolute pressure (MAP) sensor
The PCM monitors the separate feedback signals from
these sensors in order to determine their operating
status.
Diagnostic Aids
IMPORTANT:Be sure to inspect PCM and engine
grounds for being secure and clean.
A short to voltage in one of the sensor input circuits may
cause one or more of the following DTCs to be set:

P0108

P0113

P0118

P0123

P0560

P0712

P0406
IMPORTANT:If a sensor input circuit has been shorted
to voltage, ensure that the sensor is not damaged. A
damaged sensor will continue to indicate a high or low
voltage after the affected circuit has been repaired. If the
sensor has been damaged, replace it.
An open in the sensor ground circuit between the PCM
and the splice will cause one or more of the following
DTCs to be set:

P0108

P0113

P0118

P0123

P0712

P0406
A short to ground in the 5-volt reference A or B circuit will
cause one or more of the following DTCs to be set:

P0107

P0122
In the 5-volt reference circuit A, between the PCM and the
splice, will cause one or more of the following DTCs to be
set:

P0122
In the 5-volt reference circuit B, between the PCM and the
splice, will cause one or more of the following DTCs to be
set:

P0107
Check for the following conditions:

6E±68
ENGINE DRIVEABILITY AND EMISSIONS
Exhaust Gas Recirculation (EGR)
Diagnosis (For except EXPORT and
SOUTH AFRICA)
Pintle position error diagnosis is covered by DTC P0402,
P0404, P1404, P0405, P0406. If EGR diagnostic trouble
codes P0402, P0404, P1404, P0405, P0406 are
encountered, refer to the DTC charts.
Engine Tech 2 Data Definitions and
Ranges
A/C CLUTCH ± Tech 2 Displays ON or OFF ±
Indicates whether the PCM has commanded the A/C
clutch ON. Used in A/C system diagnostic.
A/C REQUEST Ð Tech 2 Displays YES or NO Ð
Indicates the state of the A/C request input circuit from the
HVAC controls. The PCM uses the A/C request signal to
determine whether A/C compressor operation is being
requested.
AIR/FUEL RATIO Ð Tech 2 Range 0.0-25.5 Ð
Air/fuel ratio indicates the PCM commanded value. In
closed loop, the air/fuel ratio should normally be
displayed around ª14.2-14.7.º A lower air/fuel ratio
indicates a richer commanded mixture, which may be
seen during power enrichment or TWC protection modes.
A higher air/fuel ratio indicates a leaner commanded
mixture. This can be seen during deceleration fuel mode.
BAROMETRIC PRESSURE Ð Tech 2 Range 10-105
kPa/0.00-5.00 Volts Ð
The barometric pressure reading is determined from the
MAP sensor signal monitored during key up and wide
open throttle (WOT) conditions. The barometric pressure
is used to compensate for altitude differences and is
normally displayed around ª61-104º depending on
altitude and barometric pressure.
CHECK TRANS LAMP Ð AUTO TRANSMISSION Ð
Indicates the need to check for a DTC with the Tech 2
when the lamp is flashing 0.2 seconds ON and 0.2
seconds OFF.
CMP ACT. COUNTER ± Cam Position Activity
DECEL FUEL MODE Ð Tech 2 Display ACTIVE or
INACTIVE Ð
ªACTIVEº displayed indicates that the PCM has detected
conditions appropriate to operate in deceleration fuel
mode. The PCM will command the deceleration fuel
mode when it detects a closed throttle position while the
vehicle is traveling over 20 mph. While in the deceleration
fuel delivered by entering open loop and decreasing the
injector pulse width.
DESIRED EGR POS. Ð Tech 2 Range 0%-100% Ð
Represents the EGR pintle position that the PCM is
commanding.
DESIRED IDLE Ð Tech 2 Range 0-3187 RPM Ð
The idle speed that the PCM is commanding. The PCM
will compensate for various engine loads based on engine
coolant temperature, to keep the engine at the desired
speed.ECT Ð (Engine Coolant Temperature) Tech 2
Range ±40
C to 151
C (±40
F to 304
F) Ð
The engine coolant temperature (ECT) is mounted in the
coolant stream and sends engine temperature
information to the PCM. The PCM applies 5 volts to the
ECT sensor circuit. The sensor is a thermistor which
changes internal resistance as temperature changes.
When the sensor is cold (high resistance), the PCM
monitors a high signal voltage and interprets that as a cold
engine. As the sensor warms (decreasing resistance),
the voltage signal will decrease and the PCM will interpret
the lower voltage as a warm engine.
EGR DUTY CYCLE Ð Tech 2 Range 0%-100% Ð
Represents the EGR valve driver PWM signal from the
PCM. A duty cycle of 0% indicates that no EGR flow is
being commanded; a 100% duty cycle indicates
maximum EGR flow commanded.
EGR FEEDBACK Ð Tech 2 Range 0.00-5.00 Volts Ð
Indicates the EGR pintle position sensor signal voltage
being monitored by the PCM. A low voltage indicates a
fully extended pintle (closed valve); a voltage near 5 volts
indicates a retracted pintle (open valve).
ENGINE LOAD Ð Tech 2 Range 0%-100% Ð
Engine load is calculated by the PCM from engine speed
and MAF sensor readings. Engine load should increase
with an increase in RPM or air flow.
ENGINE RUN TIME Ð Tech 2 Range
00:00:00-99:99:99 Hrs:Min:Sec Ð
Indicates the time elapsed since the engine was started.
If the engine is stopped, engine run time will be reset to
00:00:00.
ENGINE SPEED Ð Range 0-9999 RPM Ð
Engine speed is computed by the PCM from the 58X
reference input. It should remain close to desired idle
under various engine loads with engine idling.
FUEL PUMP Ð Tech 2 Displays ON or OFF Ð
Indicates the PCM commanded state of the fuel pump
relay driver circuit.
FUEL TRIM CELL Ð Tech 2 Range 0-21 Ð
The fuel trim cell is dependent upon engine speed and
MAF sensor readings. A plot of RPM vs. MAF is divided
into 22 cells. Fuel trim cell indicates which cell is currently
active.
FUEL TRIM LEARN Ð Tech 2 Displays NO or YES
Ð
When conditions are appropriate for enabling long term
fuel trim corrections, fuel trim learn will display ªYES.º
This indicates that the long term fuel trim is responding to
the short term fuel trim. If the fuel trim learn displays
ªNO,º then long term fuel trim will not respond to changes
in short term fuel trim.
HO2S BANK 1, SEN. 1 Ð Tech 2 Range 0-1132 mV
Ð
Represents the fuel control exhaust oxygen sensor
output voltage. Should fluctuate constantly within a range
between 10 mV (lean exhaust) and 1000 mV (rich
exhaust) while operating in closed loop.