1998 ISUZU TROOPER Coolant system

6E±158
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0172 Fuel Trim System Rich Bank 1
D06RW030
Circuit Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a ªclosed loopº
air/fuel metering system is used. While in ªclosed loop,º
the powertrain control module (PCM) monitors the Bank 1
heated oxygen sensors (HO2S) 1 and Bank 2 HO2S 1
signals and adjusts fuel delivery based upon the HO2S
signal voltages. A change made to fuel delivery will be
indicated by the long and short term fuel trim values which
can be monitored with a Tech 2. Ideal fuel trim values are
around 0%; if the HO2S signals are indicating a lean
condition the PCM will add fuel, resulting in fuel trim
values above 0%. If a rich condition is detected, the fuel
trim values will be below 0%, indicating that the PCM is
reducing the amount of fuel delivered. If an excessively
rich condition is detected on Bank 1, the PCM will set DTC
P0172.
The PCM's maximum authority to control long term fuel
trim allows a range between ±15% (automatic
transmission) or ±12 (manual transmission) and +20%.The PCM's maximum authority to control short term fuel
trim allows a range between ±11% and +20%. The PCM
monitors fuel trim under various engine speed/load fuel
trim cells before determining the status of the fuel trim
diagnostic.
Conditions for Setting the DTC

No Tech 2 test is being run.

None of the following was set: EGR DTCs, HO2S
DTCs, (response, transition, open, low volts, no
activity), MAF DTCs, TPS DTCs, MAP DTCs, IAT
DTCs, canister purge DTCs, EVAP DTCs, injector
circuit DTCs, or misfire DTCs.

Engine coolant temperature is between 25
C (77
F)
and 100
C (212
F).

Intake air temperature is between ±40
C (±40
F) and
120
C (248
F).

Manifold absolute pressure is between 24 kPa and 99
kPa.

Throttle angle is steady below 95%.

6E±162
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0174 Fuel Trim System Lean Bank 2
D06RW031
Circuit Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a ªclosed loopº
air/fuel metering system is used. While in ªclosed loop,º
the powertrain control module (PCM) monitors the Bank 1
HO2S 1 and Bank 2 HO2S 1 signals and adjusts fuel
delivery based upon the HO2S signal voltages. A change
made to fuel delivery will be indicated by the long and
short term fuel trim values which can be monitored with a
Tech 2. Ideal fuel trim values are around 0%; if the HO2S
signals are indicating a lean condition the PCM will add
fuel, resulting in fuel trim values above 0%. If a rich
condition is detected, the fuel trim values will be below
0%, indicating that the PCM is reducing the amount of fuel
delivered. If an excessively lean condition is detected on
Bank 2, the PCM will set DTC P0174.
The PCM's maximum authority to control long term fuel
trim allows a range between ±15%(automatic
transmission) or ±12%(manual transmission) and +20%.
The PCM monitors fuel trim under various enginespeed/load fuel trim cells before determining the status of
the fuel trim diagnostic.
Conditions for Setting the DTC

No Tech 2 test is being run.

None of the following DTCs are set: idle system, EGR,
HO2S, (response, transition, open, low volts, no
activity), MAF, TP sensor, MAP, IAT, canister purge,
EVAP, injector circuit, or misfire.

Engine coolant temperature is between 25
C (77
F)
and 100
C (212
F).

Intake air temperature is between ±40
C (±40
F) and
120
C (248
F).

Manifold absolute pressure is between 24 kPa and 99
kPa.

Throttle angle is steady below 95%.

Vehicle speed is below 136 km/h (85 mph).

Engine speed is between 400 and 6,000 RPM.

Barometric pressure is greater than 72.5 kPa.

Mass air flow is between 2 g/second and 200 g/second.

6E±166
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0175 Fuel Trim System Rich Bank 2
D06RW031
Circuit Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a ªclosed loopº
air/fuel metering system is used. While in ªclosed loop,º
the powertrain control module (PCM) monitors the Bank 1
HO2S 1 and Bank 2 HO2S 1 signals and adjusts fuel
delivery based upon the HO2S signal voltages. A change
made to fuel delivery will be indicated by the long and
short term fuel trim values which can be monitored with a
Tech 2. Ideal fuel trim values are around 0%; if the HO2S
signals are indicating a lean condition the PCM will add
fuel, resulting in fuel trim values above 0%. If a rich
condition is detected, the fuel trim values will be below
0%, indicating that the PCM is reducing the amount of fuel
delivered. If an excessively rich condition is detected on
Bank 2, the PCM will set DTC P0175.
The PCM's maximum authority to control long term fuel
trim allows a range between ±15%(automatic
transmission) or ±12%(manual transmission) and +20%.
The PCM's maximum authority to control short term fueltrim allows a range between ±11% and +20%. The PCM
monitors fuel trim under various engine speed/load fuel
trim cells before determining the status of the fuel trim
diagnostic.
Conditions for Setting the DTC

No Tech 2 test is being run.

None of the following DTCs are set: idle system, EGR,
HO2S, (response, transition, open, low volts, no
activity), MAF, TPS, MAP, IAT, canister purge, EVAP,
injector circuit, or misfire.

Engine coolant temperature is between 25
C (77
F)
and 100
C (212
F).

Intake air temperature is between ±40
C (±40
F) and
120
C (248
F).

Manifold absolute pressure is between 24 kPa and 99
kPa.

Throttle angle is steady below 95%.

Vehicle speed is below 136 km/h (85 mph).

Engine speed is between 400 and 6,000 RPM.

6E±245 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1171 Fuel System Lean During Acceleration
060RW193±1
Circuit Description
The powertrain control module (PCM) internal circuitry
can identify if the vehicle fuel system is capable of
supplying adequate amounts of fuel during heavy
acceleration (power enrichment). The PCM monitors the
voltage of the oxygen sensor during power enrichment.
When a power enrichment mode of operation is
requested during ªclosed loopº operation (by heavy
acceleration), the PCM will provide more fuel to the
engine. Under these conditions the PCM should detect a
ªrichº condition (high oxygen sensor voltage). If this ªrichº
exhaust is not detected at this time, a DTC P1171 will set.
A plugged fuel filter, restricted fuel line, restricted in-tank
filter or defective fuel pump can prevent adequate
amounts of fuel from being supplied during power
enrichment mode.
Conditions for Setting the DTC

No related DTCs.
Engine is operating in ªclosed loop power enrichmentº
mode for 3 seconds.

Engine coolant temperature is above 60
C (140
F).

While in ªpower enrichmentº mode the oxygen sensor
voltage remains below 400 mV for 3 seconds.
Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp
(MIL) the first the fault is detected.

The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC

DTC P1171 can be cleared by using Tech 2 ªClear Infoº
function or by disconnecting the PCM battery feed.
Diagnostic Aids

A restricted fuel filter or fuel line, restricted in-tank filter,
or a defective fuel pomp may supply adequate

6E±251 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1508 IAC System Low RPM
T321115
Circuit Description
The powertrain control module (PCM) controls engine
idle speed by adjusting the position of the idle air control
(IAC) motor pintle. The IAC is a bi-directional stepper
motor driven by two coils. The PCM applies current to the
IAC coils in steps (counts) to extend the IAC pintle into a
passage in the throttle body to decrease air flow. The
PCM reverses the current to retract the pintle, increasing
air flow. This method allows highly accurate control of idle
speed and quick response to changes in engine load. If
the PCM detects a condition where too low of an idle
speed is present and the PCM is unable to adjust idle
speed by increasing the IAC counts, DTC P1508 will set,
indicating a problem with the idle control system.
Conditions for Setting the DTC

No Tech 2 test is being run.

None of these DTCs are set: TP sensor, VSS, ECT,
EGR, fuel system, MAF, MAP, IAT, canister purge,
injector control or ignition control.

Barometric pressure is above 75 kPa.

Engine coolant temperature (ECT) is above 50
C
(120
F).

Engine speed is more than 100-200 RPM lower than
desired idle, based upon coolant temperature.

The engine has been running for at least 125 seconds.

Vehicle speed is less than 1 mph.

Canister purge duty cycle is above 10%.

Ignition voltage is between 9.5 volts and 16.7 volts.
The throttle is closed.

Engine speed is lower than desired idle.

All of the above conditions are met for 10 seconds.
Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.

The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC

DTC P1508 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:

Poor connection at PCM or IAC motor ± Inspect
harness connectors for backed-out terminals,
improper mating, broken locks, improperly formed or
damaged terminals, and poor terminal-to-wire
connection.

Damaged harness ± Inspect the wiring for damage.

Restricted air intake system ± Check for a possible
collapsed air intake duct, restricted air filter element,
or foreign objects blocking the air intake system.

Throttle body ± Check for objects blocking the IAC
passage or throttle bore, excessive deposits in the IAC

6E±254
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1509 IAC System High RPM
T321115
Circuit Description
The powertrain control module (PCM) controls engine
idle speed by adjusting the position of the idle air control
(IAC) motor pintle. The IAC is a bi-directional stepper
motor driven by two coils. The PCM applies current to the
IAC coils in steps (counts) to extend the IAC pintle into a
passage in the throttle body to decrease air flow. The
PCM reverses the current to retract the pintle, increasing
air flow. This method allows highly accurate control of idle
speed and quick response to changes in engine load. If
the PCM detect a condition where too high of an idle
speed is present and the PCM is unable to adjust idle
speed by increasing the IAC counts, DTC P1509 will set,
indicating a problem with the idle control system.
Conditions for Setting the DTC

No Tech 2 test is being run.

None of these DTCs are set: TP sensor, VSS, ECT,
EGR, fuel system, MAF, MAP, IAT, canister purge,
injector control or ignition control.

Barometric pressure is above 75 kPa.

Engine coolant temperature is above 50
C (120
F).

Engine speed is more than 100-200 RPM lower than
desired idle, based upon coolant temperature.

The engine has been running for at least 125 seconds.

Vehicle speed is less than 1 mph.

Canister purge duty cycle is above 10%.

Ignition voltage is between 9.5 volts and 16.7 volts.

Engine speed is lower than desired idle.
All of the above conditions are met for 5 seconds.
Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.

The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC

DTC P1509 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:

Poor connection at PCM or IAC motor ± Inspect
harness connectors for backed-out terminals,
improper mating, broken locks, improperly formed or
damaged terminals, and poor terminal-to-wire
connection.

Damaged harness ± Inspect the wiring for damage.

Vacuum leak ± Check for a condition that causes a
vacuum leak, such as disconnected or damaged
hoses, leaks at the EGR valve and the EGR pipe to the
intake manifold, leaks at the throttle body, faulty or
incorrectly installed PCV valve, leaks at the intake
manifold, etc.

6E±263 ENGINE DRIVEABILITY AND EMISSIONS
Hard Start Symptom

StepActionValue(s)Ye sNo
1DEFINITION: Engine cranks, but does not start
for a long time. Does eventually run, or may start
but immediately stalls.
Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found,
correct the condition as instructed in the bulletin.
Was a bulletin found that addresses the symptom?
ÐVerify repairGo to Step 3
3Was a visual/physical check performed?
ÐGo to Step 4
Go to
Visual/Physic
al Check
4Check engine coolant temperature (ECT) sensor for
shift in value. After 8 hours with the hood up and the
engine not running, connect Tech 2. With the ignition
ªONº and the engine not running, compare engine
coolant temperature to intake air temperature.
Are ECT and IAT within the specified value of each
other?
+ 5
C (+ 9
F)Go to Step 8Go to Step 5
51. Using Tech 2, display the engine coolant
temperature and note the value.
2. Check the resistance of the engine coolant
temperature sensor.
3. Refer to
Engine Coolant Temperature Sensor
Temperature vs. Resistance
chart on DTC P0118
Diagnostic Support
for resistance specifications.
Is the resistance value near the resistance for the
temperature noted?
ÐGo to Step 7Go to Step 6
6Replace the ECT sensor.
Is the action complete?
ÐVerify repairÐ
7Locate and repair high resistance or poor connection in
the ECT signal circuit or the ECT sensor ground.
Is the action complete?
ÐVerify repairÐ
81. Check for a faulty, plugged, or incorrectly installed
PCV valve.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 9
91. Check for water- or alcohol-contaminated fuel.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 10
101. Perform the procedure in Fuel System Pressure
Test
.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 11
111. Check for proper ignition voltage output with spark
tester J 26792 (ST-125). Refer to
Electric Ignition
System
for procedure.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 12

6E±270
ENGINE DRIVEABILITY AND EMISSIONS
Detonation/Spark Knock Symptom

StepActionValue(s)Ye sNo
1DEFINITION:
A mild to severe ping, usually worse under acceleration.
The engine makes sharp metallic knocks that change
with throttle opening.
Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found,
correct the condition as instructed in the bulletin.
Was a bulletin found that addresses the symptom?
ÐVerify repairGo to Step 3
3Was a visual/physical check performed?
ÐGo to Step 4
Go to
Visual/Physic
al Check
4If Tech 2 readings are normal (refer to Typical Scan
Values
) and there are no engine mechanical faults, fill
the fuel tank with a known quality gasoline that has a
minimum octane rating of 87 and re-evaluate the
vehicle performance.
Is detonation present?
ÐGo to Step 5Verify repair
51. Check the transmission range switch circuit. Use
Tech 2 and be sure Tech 2 indicates that the vehicle
is in drive with the gear selector in drive or overdrive.
2. If a problem is found, diagnose and repair the
transmission range switch as necessary (refer to
4L30-E Automatic Transmission Diagnosis).
Was a problem found?
ÐVerify repairGo to Step 6
61. Check TCC operation. Refer to 4L30-E
Transmission Diagnosis
.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 7
71. Check for obvious overheating problems:

Low engine coolant.

Restricted air flow to radiator, or restricted
water flow through radiator.

Correct coolant solution should be a 50/50 mix
of approved antifreeze/coolant and water.
Refer to
Engine Cooling.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 8
81. Check fuel pressure. Refer to Chart Fuel System
Pressure Test.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 9
91. Check items that can cause an engine to run lean
(long term fuel trim significantly in the positive
range). For a lean condition, refer to
Diagnostic
Aids
in DTC P0171 Diagnostic Support.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 10