1995 ISUZU TROOPER Workshop Manual

CD
®
DRIVEABILITY AND EMISSIONS 6E2-81
DIAGNOSTIC TROUBLE CODE (DTC) 42
IGNITION CONTROL (IC) CIRCUIT
• CLEAR DIAGNOSTIC TROUBLE CODES (DTCs). • IDLE ENGINE FOR 1 MINUTE OR UNTIL DTC 42 SETS.
DOES DTC 42 SET?
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• IGNITION "OFF" DTC 42 INTERMITTENT.
• DISCONNECT ENGINE CONTROL MODULE (ECM) REFER TO "DIAGNOSTIC AIDS" ON
CONNECTORS. FACING~ • IGNITION "ON".
• OHMMETER SELECTOR SWITCH IN THE 1 000 TO 2000
OHMS RANGE. • PROBE ECM HARNESS CONNECTOR IGNITION CONTROL (IC) CKT WITH AN OHMMETER TO GROUND. IT SHOULD READ LESS THAN 1000 OHMS.
DOES IT?
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• PROBE ECM HARNESS CONNECTOR BYPASS CKT WITH OPEN IC CKT, FAULTY CONNECTION OR FAULTY
I A TEST LIGHT TO BATTERY POSITIVE VOLTAGE. ELECTRONIC IGNITION MODULE.
L LIGHT "OFF" I LIGHT "ON" I
I
• WITH OHMMETER STILL CONNECTED TO ECM HARNESS • DISCONNECT IC MODULE 4-wAY CONNECTOR. IC CKT AND GROUND. L AGAIN PROBE ECM HARNESS BYPASS CKT WITH THE TEST
I I
LIGHT CONNECTED TO BATTERY VOLTAGE. (AS TEST LIGHT
LIGHT "ON" j LIGHT"OFF" I CONTACTS BYPASS CKT, RESISTANCE SHOULD SWITCH
FROM UNDER 1000 TO OVER 2000 OHMS.) I l DOES IT? BYPASS CKT SHORTED I FAULTY IGNITION I
TO GROUND. MODULE.
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•
DISCONNECT 6-WAY CONNECTOR AT ELECTRONIC ® • RECONNECT ECM AND IDLE ENGINE FOR ONE
IGNITION MODULE. MINUTE OR UNTIL CODE 42 SETS.
NOTE OHMMETER THAT IS STILL CONNECTED TO
DOES CODE SET? IC CKT AND GROUND. RESISTANCE SHOULD HAVE GONE I HIGH (OPEN CIRCUIT).
DOES IT?
$ $
$ $
FAULTY ECM I DTC 42 INTERMITTENT. REFER TO "DIAGNOSTIC
AIDS" ON FACING
BYPASS
CKT OPEN, IIC CKT SHORTED TO ~ FAULTY CONNECTIONS GROUND. OR FAULTY IGNITION MODULE.

6E2-82 DRIVEABILITY AND EMISSIONS
Circuit Description:
DIAGNOSTIC TROUBLE CODE (DTC) 43
KNOCK SENSOR (KS) CIRCUIT
(DOHC)
Knock Sensor (KS) is accomplished with a module that sends a voltage signal to the Engine Control Module (ECM).
As the KS detects engine knock, the voltage from the KS module to the ECM drops, and this signals the ECM to
retard timing. The ECM will retard the timing when knock is detected and revolution per minute is above about 880
revolution
per minute.
Diagnostic
Trouble Code (DTC) 43 means the ECM has been low voltage at CKT 010 for longer than 4.0 seconds
with the engine running or the system has
failed the functional check.
DTC 43 will set when:
• After run spark, more than 4 seconds
• KS input signal has been low more than 4 seconds
Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
CD If the conditions for a DTC 43 are present the "Scan tool" will always display "YES". There should not be a
knock at
idle unless an internal engine problem, or a system problem exists.
® This test will determine if the system is functioning at this time. Usually a KS signal can be generated by
tapping on the right exhaust
manifold. If no KS signal is generated try tapping on block close to the area of the
sensor.
® Because DTC 43 sets when the signal voltage on CKT 010 remains low this test should cause the signal on
CKT to go high. The 12 volts signal should be seen by the ECM as "no knock" if the ECM and wiring are OK.
@ This test will determine if the KS signal is being detected on CKT WHT or if the KS module is at faulty.
@ If CKT WHT is routed is close to secondary ignition wires the KS module may see the interference as a KS
signal. ~
® This checks the ground circuitto the module. An open ground will cause the voltage on CKT 010 to be about 5
volts which would cause the DTC 43 functional test to fail.
(J) Contacting CKT WHT with a test light to 5 volts should generate a KS signal. This will determine if the KS
module is operating correctly.
Diagnostic Aids: DTC43 can be caused by a faulty connection atthe KS module or atthe ECM. Also check CKT
010 for possible open or short to ground.
Refer
to "lntermittents" in "Symptoms," Section "6E2-B".
TWO-WAY CONNECTOR
BLACK AT REAR OF INTAKE
-' / I I
WHT
BLK!YEL
LOCATED REAR OF 0 INTAKE PLENUM
1-----L T GRN/YEL
KNOCK
SENSOR
MODULE
BLK/YEL
GROUND
TOECM ~ TERMINAL ENGINE A12 GROUND
0 LOCATEDAT _ DRIVER'S SIDE REAR OF CYLINDER HEAD
Fig. 6E2-46
RED/GRN
+ TO MAIN RELAY
ENGINE CONTROL MODULE(ECM)
KNOCK SENSOR SIGNAL INPUT

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DRIVEABILITV AND EMISSIONS 6E2-83
• ENGINE IDLING.
DIAGNOSTIC TROUBLE CODE (DTC) 43
KNOCK SENSOR (KS) CIRCUIT
(DOHC)
• "SCAN TOOL" SET ON KNOCK SENSOR (KS} SIGNAL. IS THERE A KS SIGNAL INDICATED?
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• DISCONNECT KS MODULE. ® • ENGINE IDLING.
• ENGINE IDLING. • TAP ENGINE BLOCK IN AREA OF KS. • PROBE HARNESS TERMINAL "C" (CKT • IS A KS SIGNAL INDICATED WHILE TAPPING ON
D10} WITH A TEST LIGHT CONNECTED
ENGINE?
TO 12 VOLTS. AFTER SECONDS, DOES "SCAN TOOL"
DISPLAY A KS SIGNAL?
$ ~ ~ ~ • IGNITION "ON". CKT D10 OPEN, @ • DISCONNECT KS MODULE. DIAGNOSTIC
TROUBLE
• PROBE TERMINAL SHORTED TO • PROBE HARNESS TERMINAL "D" CODE 43 IS INTERMITTENT. "D" WITH A TEST
GROUND, OR WITH A TEST LIGHT TO 12V. IF NO ADDITIONAL
LIGHT TO GROUND. FAULTY ENGINE DIAGNOSTIC TROUBLE
CONTROL CODES WERE STORED,
MODULE.
REFER TO "DIA~= AIDS" ON FAGIN .
I I
LIGHT "ON" I LIGHT "OFF" I LIGHT "ON" j LIGHT "OFF" I
I
I
• REMOVE TERMINAL TERMINAL "D" (J) • RECONNECT KS MODULE. REPAIR
OPEN GROUND I "E" FROM
OPEN, • DISCONNECT KS . CONNECTOR.
SHORTED TO • ENGINE IDLING.
• RECONNECT KS GROUND. • MOMENTARILY TOUCH KS MODULE.
HARNESS IS TERMINAL "E" • ENGINE IDLING. WITH A TEST LIGHT TO 12V. IS THERE A KS • EACH TIME THE TEST LIGHT
SIGNAL INDICATED?
CONTACTS TERMINAL "E", A KS SIGNAL SHOULD BE GENERATED. • IS A KS SIGNAL
INDICATED WITH "SCAN TOOL"?
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~
FAULTY CONNECTION AT SENSOR TERMINAL "E" OPEN. OR FAULTY KS. SHORTED
TO GROUND,
~
FAULTY CONNECTION AT KS MODULE, OR FAULTY KS MODULE. FAULTY @ • IF AN AUDIBLE KNOCK CAN BE HEARD, CONNECTION
REPAIR INTERNAL ENGINE PROBLEM. IF OK, OR CHECK FOR ROUTING OF WIRE FROM KS TO KS MODULE. KS MODULE FOR PICKING UP FALSE KS SIGNALS FROM AN ADJACENT WIRE.
REROUTE AS NECESSARY. IF ROUTING IS CORRECT, REPLACE KS.

6E2-84 DRIVEABILITY AND EMISSIONS
DIAGNOSTIC TROUBLE CODE (DTC) 44
HEATED OXYGEN SENSOR (H02S) CIRCUIT
(LEAN HEATED OXYGEN SENSOR (H02S) SIGNAL INDICATED)
Circuit Description:
The engine control module supplies a voltage of about .43 volt between terminals "83" and "82". (If measured
with a
10 megohm digital voltmeter, this may read as low as .32 volts.) The Heated Oxygen Sensor (H02S) varies
the
voltage within a range of about 1 volt, if the exhaust is rich, down through about .1 0 volt, if exhaust is lean.
The sensor is like an open circuit and produces no voltage, when it is below about 360°C (600°F). An open sensor
circuit,
or cold sensor, cause "Open Loop" operation.
Test Description:
Numbers below refer to circled numbers on the diagnostic chart.
CD Diagnostic Trouble Code (DTC) 44 is set, when the 02S signal voltage is fixed below .1 00 mV and the
following:
• Throttle
position sensor greater than 9.8%.
• No DTC 21 or 33. • Oxygen signal voltage is steady between .347
volt and .547 volt.
•
The engine has been running at least for 180 •
seconds. • • System is operating in "Closed Loop". •
Engine Operation Temperature 69SC (155°F).
All of the above conditions present for 25 sec .
Integrator not at 128 .
Diagnostic Aids:
Using the "Scan tool", observe the block learn value at different revolution per minute. The "Scan tool" also
displays
the block cells, so the block learn values can be checked in each ofthe cells, to determine when the DTC 44
may have been set.
If the conditions for DTC 44 exist, the block learn values will be around 150.
•
Check for ground in wire between connector sensor.
• Fuel Contamination-Water, even in small amounts, near the in-tank fuel pump inlet can be delivered to the
injector. The water causes a
lean H02S signal and can set a DTC 44.
• Fuel Pressure-System will be lean if pressure is too low. If may be necessary to monitor fuel pressure,
while driving the car at various road speeds and/or loads to confirm. See Fuel System diagnosis CHART A-5.
• Exhaust Leaks -lfthere is an exhaust leak, the engine can cause outside air to be pulled into the exhaust and
past the sensor.
Vacuum or crankcase leaks can cause a lean condition.
• If DTC 44 is intermittent, refer to Section "6E2-8".
• Fuel
Injectors-The wrong fuel injector(s) could be the cause of a lean H02S signal condition. Verify that the
correct
fuel injector(s) are installed in the vehicle. Refer to the service parts manual for correct part and part
number.
Refer
to "Engine Control Module and Sensors", Section "6E2-C1" for proper diagnosis.
TRANSMISSION
HARNESS
CONNECTOR
~BLK1
TRANSMISSION
HARNESS CONNECTOR
(BLUE) I /' BL~GRN~r-~----------~-------BLU
RED/BLU (MfT) --(( 1
1 ; « RED
(BLUE) ~
PASSENGER Q SIDE
LT BLU (A/T) L
WHT/RED 1
P:::l=t=t1 l BL~GRN ----.-----BL~GRN
BLK!YEL BL~BLU FENDER 02 --·S HEATER ELEMENT l
ENGINE
DRIVER'S SIDE BLOCK REAR AT CYLINDER
TRANSMISSION HARNESS _ HEAD CONNECTOR (BLUE)
10A -----BL~GRN ____ .,.... ~3EL PUMP RELAY
Fig. 6E2-47
ENGINE CONTROL
MODULE(ECM)
H02SGROUND REFERENCE
H02SSIGNAL
ECM GROUNDS
ECM GROUNDS
..