Isuzu 2000 Trooper Workshop Manual page 1099

6E–230
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Conditions for Clearing the MIL/DTC
D The PCM will turn the MIL "OFF" on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.
D A history DTC P0172 will clear after 40 consecutive
warm-up cycles have occurred without a fault.
D DTC P0172 can be cleared by using the Tech 2 "Clear
Info" function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:
D Poor connection at PCM – Inspect harness connectors
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 be OK, observe the
Bank 1 HO2S 1 display on the Tech 2 while moving
connectors and wiring harnesses related to the engine
Step
1 Was the "On-Board Diagnostic (OBD) System Check"
performed?
2 Are any DTCs set other than P0172 and P0175?
3 1. Start the engine and operate the vehicle in "closed
loop."
2. Observe "B1 Long Term Fuel Trim" display on the
Tech 2.
Is the displayed value more negative than the specified
value?
4 1. Review and record the Tech 2 Failure Records data.
2. Clear the DTC P0172/P0175 and operate the
vehicle to duplicate the Failure Records conditions.
3. Monitor the Tech 2 "DTC" info for DTC P0172 while
operating the vehicle to duplicate the Failure
Records conditions.
4. Continue operating the vehicle until the DTC P0172
test runs and note test result.
Does the Tech 2 indicate DTC P0172 failed this
ignition?
5 Is DTC P0175 also set?
6 Visually and physically inspect the air filter element and
replace it if necessary.
Did the air filter require replacement?
DTC P0172 – Fuel Trim System Rich Bank 1
Action
harness. A change in the display will indicate the
location of the fault.
Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the DTC to be set occurs. This
may assist in diagnosing the condition.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. DTCs other than P0172 and P0175 may indicate a
condition present which may cause a lean condition.
If this is the case, repairing the condition which
caused the other DTC will most likely correct the
DTC P0172/P0175.
4. If the DTC P0172 test passes while the Failure
Records conditions are being duplicated, the rich
condition is intermittent. Refer to Diagnostic Aids or
Symptoms for additional information on diagnosing
intermittent problems.
Value(s)
— Go to Step 2
Go to the
applicable
DTC charts
and repair the
other DTCs
proceeding
— with this chart
L.T. Fuel
Trim: –15%
(auto. trans.)
OR –12%
Go to Step 5
(man. trans.)
— Go to Step 5
— Go to Step 6
— Verify repair
Yes No
Go to OBD
System
Check
before
Go to Step 3
Go to Step 4
The rich
condition is
not present.
If a
driveability
symptom still
exists, refer
to Symptoms .
Go to Step 15
Go to Step 7