1995 ISUZU TROOPER Workshop Manual

®
.... /"{ rtS (ill .. , (. --f (.'' \J DRIVEABILITV AND EMISSIONS 6E2-41
CHART A-2
NO DATA LINK CONNECTOR (DLC) DATA OR
WILL NOT FLASH DIAGNOSTIC TROUBLE CODE (DTC) 12
"CHECK ENGINE" MALFUNCTION INDICATOR LAMP (MIL) "ON" STEADY
• IGNITION "ON", ENGINE "OFF". IS THE "CHECK ENGINE" MALFUNCTION INDICATOR LAMP (MIL) "ON"?
~ $
• GROUND DATA LINK CONNECTOR, DIAGNOSTIC USE CHART A-1 I TERMINAL "1" AND "3". DOES LIGHT FLASH DIAGNOSTIC TROUBLE CODE (DTC) 12?
$ $
• IGNITION "OFF". G) IF PROBLEM WAS NO DATA LINK CONNECTOR
• DISCONNECT ENGINE CONTROL MODULE (ECM) DATA: CHECK SERIAL DATA CIRCUIT FOR OPEN OR CONNECTORS.
SHORT TO GROUND BETWEEN ECM AND DATA • IGNITION "ON" AND NOTE MIL LINK CONNECTOR. IF OK, IT IS A FAULTY ECM.
I LIGHT "OFF" I LIGHT "ON" j
I • IGNITION "OFF". REPAIR SHORT TO GROUND IN MIL CIRCUIT.
• RECONNECT ECM.
• IGNITION "ON", ENGINE "OFF",
DIAGNOSTIC TEST TERMINAL NOT GROUNDED.
• BACK
PROBE ECM TERMINAL "C4" WITH TEST
LIGHT TO GROUND.
LEAVE CONNECTED AND WATCH MIL.
I NO DTC 12 I DTC 12 I
I REPLACE ECM I CHECK FOR OPEN IN ORNIYEL WIRE. IF OK, CHECK FOR OPEN CIRCUIT BETWEEN DATA LINK CONNECTOR TERMINAL "3" AND GROUND.
CLEAR DTC(S) AND CONFIRM "CLOSED LOOP" OPERATION AND NORMAL"CHECK ENGINE" MALFUNCTION INDICATOR LAMP OPERATION.

6E2-42 DRIVEABILITV AND EMISSIONS
CHART A-3
(Page 1 of 3)
ENGINE CRANKS BUT WILL NOT RUN
Circuit Description:
Before using this chart, battery condition, engine cranking speed, and fuel quantity should be checked and verified
as being OK.
Test Description:
Numbers below refer to circled numbers on the diagnostic chart.
CD A malfunction indicator lamp "ON" is basic test to determine if there is battery positive voltage and ignition
voltage supplied to the Engine Control Module (ECM). No data link connector data may be due to an ECM
problem. CHART A-2 will diagnose the ECM. If throttle position sensor voltage is over 2.5 volts, the engine
may be in the
"clear flood" mode, which will cause starting problems. The engine will not start without
reference pulses and, therefore, the "Scan tool" should indicate engine speed during cranking.
@ Because the electronic ignition system uses two plugs and wires to complete the circuit of each coil, the
opposite spark
should be left connected. If revolution per minute was indicated during crank, the ignition
control module is receiving a crank signal, but no spark at this test indicates the Ignition Control Module (ICM)
is not triggering the coils.
® The test light should blink, indicating the ECM is in control of the injectors. How bright the light blinks is not
important. However, the test light should be a J-34730-3 or equivalent.
@ This test will determine if the ignition control module is not generating the reference pules or if the wiring or
ECM are at fault. By touching and removing a test light to 12 volts on VEL/RED wire, a reference pulse should
be generated. If revolution per minute is indicated, the ECM and wiring are OK.
® High resistance in the spark plug wire could cause a "no start" condition. If a spark plug wire is found to be
faulty, replace it and retest system.
(SOHC)
I"M"
TOECM RED/GRN #1 BLU/YEL MAIN RED/GRN #2 BLU/YEL
RELAY
tRED/GRN
RED/GRN #3 BLU/YEL
RED/GRN #4 BLU/YEL
RED/GRN
#5 BLU/YEL
RED/GRN
#6 BLU/YEL
FUEL
INJECTORS ENGINE
CONTROL MODULE(ECM)
INJECTOR
RED/GRN
RED/GRN
RED/GRN
RED/GRN
RED/GRN
RED/GRN
IDOHCI BLU/YEL
BLU/YEL
l 1.3!l INJECTOR RESISTOR 1_
ORG/BLU
--+----
E~INE YEL/GRN D11 BLK/ORN -4>-BLK/YEL ----41sv---TO IGN BLK/RED -TOTACHOMETER SWITCH
BLK --:::L =
AND TCM (C91-D12)
CRANKSHAFT
POSITION
1 SENSOR
-........:::SHIELD
Fig. 6E2-26
•

DRIVEABILITY AND EMISSIONS 6E2-43
CHART A-3
-JJ!atfe 1 of 3)
ENGINE CRANKS BUT WILL NOT RUN
Q) • IGNITION "ON", IF "CHECK ENGINE" MALFUNCTION INDICATOR LAMP IS "OFF", SEE CHART A-1. • INSTALL TECH 1 "SCAN TOOL". IF "NO DATA LINK CONNECTOR", SEE CHART A-2. • CHECK THE FOLLOWING: THROTTLE POSITION SENSOR-IF OVER 2.5V AT CLOSED THROTTLE, SEE DIAGNOSTIC
TROUBLE CODE 21. IS REVOLUTION PER MINUTE INDICATED DURING CRANKING?
® • USING AN ST-125 (SPARK CHECKER) CHECK FOR SPARK ON TWO WIRES (2-4 OR 4-6).
® • USING AN ST-125 (SPARK CHECKER) J-26792 OR EQUIVALENT, CHECK FOR SPARK ON TWO WIRES (2-4 OR 4-6).
• CHECK ONE WIRE AT A TIME. LEAVE THE OTHER WIRES CONNECTED TO SPARK PLUG
WHILE CRANKING.
IS THERE SPARK ON BOTH
WIRES?
@ • DISCONNECT THE ENGINE HARNESS BLACK CONNECTOR
(DOHC) OR BLUE CONNECTOR (SOHC).
• USING A TEST LIGHT CONNECTED TO BATTERY POSITIVE VOLTAGE. • PROBE THE BLUIYEL
WIRE AT THE BLACK CONNECTION AND THE
BLU/GRN WIRE AT THE BLUE CONNECTOR
WHILE CRANKING THE ENGINE.
TEST LIGHT SHOULD
BLINK ON BOTH, DID
IT?
FAULTY IGNITION
MODULE
REFER TO L-----------1 CHART A-3
~20F3)
• CHECK ONE WIRE AT A TIME. LEAVE THE OTHER WIRES CONNECTED TO SPARK PLUG WHILE CRANKING. IS THERE SPARK ON BOTH WIRES?
NO SPARK
@ • IGNITION "OFF". SEE CHART A-3 (eA8£3 OF 3)
SPARK ON ONE
@ CHECK PAIR OR WIRES THAT DID
NOT SPARK.
EACH WIRE SHOULD MEASURE
LESS THAN 30,000 OHMS. IF OK, SWITCH COIL
ASSEMBLIES. DOES PROBLEM MOVE? •
DISCONNECT IGNITION
6-WAY CONNECTOR.
• IGNITION "ON". • MOMENTARILY TOUCH VEL/RED WIRE WITH A TEST
LIGHT TO 12 VOLTS WHILE
OBSERVING ENGINE SPEED.
IS REVOLUTION PER MINUTE
INDICATED?
VEL/RED WIRE OPEN OR SHORTED TO
GROUND
OR FAULTY ENGINE
CONTROL MODULE
CLEAR DIAGNOSTIC TROUBLE CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NORMAL "CHECK ENGINE" MALFUNCTION
INDICATOR LAMP OPERATION.

6E2-44 DRIVEABILITV AND EMISSIONS
CHART A-3
(Page 2 of 3)
ENGINE CRANKS BUT WILL NOT RUN
Test Description:
Numbers below refer to circled numbers on the diagnostic chart.
CD This will check the injector harness for an "open" or "shorted" circuit after the engine harness connector.
® A shorted or resistance injector could be the cause of a "cranks but won't run" symptom.
® Test for a short to ground in the injector driver circuits.
@ Check for voltage at the injector. An "open" in the RED/GRN wire at the splice from the main relay would
result in a "crank but won't run" symptom.
@ Test the engine control module for a injector pulse.
® A faulty resistor module could be the cause of a no start. If module was found to be faulty, recheck the engine
control module after replacement of the resistor module.
INJECTOR
RED/GRN BLU!YEL
RED/GRN
RED/GRN
(SOHC) RED/GRN
RED/GRN
1,------RED/GRN --------t~-R-E-D/:_G_R_N----'
TOECM MAIN RELAY
LED/GRN
RED/GRN #1 BLU!YEL
RED/GRN
#2 BLU!YEL
RED/GRN #3 BLU!YEL
RED/GRN #4 BLU!YEL
RED/GRN #5 BLU!YEL
RED/GRN #6 BLU!YEL
FUEL
INJECTORS (DOHC)
BLU!YEL
BLU!VEL1 INJECTOR
RESISTOR BLU/GRN
L ORG/BLU ----411f----ORG/BLU
c__ __ ORG/BLU
~---------------VEL
~---------------YE~RED
~-----------------YE~BLU
~--------------~ YE~GRN D11 Ef'WINE . BLKJORN ~>-
BLKJRED _____.
BLK -::L
BLK/YEL ___.,5~ TO IGN
TO TACHOMETER SWITCH
AND TCM (C91-D12)
WHT----i:'---'r,--1 CRANKSHAFT
BLK --___.~ i POSITION ' :
1 SENSOR WHT/RED ~~,_7,::-L!...LJ
'SHIELD
Fig. 6E2-27
ENGINE CONTROL
MODULE(ECM)
1 and 2 fuel injector
3 and 4
fuel injector
5 and 6
fuel injector
•

DRIVEABILITV AND EMISSIONS 6E2-45
CHART A-3
.(hfi 2 of 3)
ENGINE CRANKS BUT WILL NOT RUN
FROM CHART A-3 (1 OF 3) I l j_ I
BLINKING LIGHT I STEADY LIGHT I NO LIGHT j
I
I @ • RECONNECT THE BLUE AND @ • IGNITION "OFF". •
BACK PROBE ECM AT TERMINAL BLACK ENGINE HARNESS • DISCONNECT ENGINE CONTROL C11,
C14, D15 AND D16 WITH
CONNECTORS. MODULE (ECM) CONNECTORS. TEST LIGHT TO BATTERY • REFER TO $E.CR01111:2 FOR • PROBE ECM TERMINALS C11, POSITIVE
VOLTAGE.
INTAKE PLENUM REMOVAL. C14, D15 AND D16 WITH TEST •
NOTE LIGHT WHILE CRANKING,
• WITH INTAKE PLENUM REMOVE LIGHT TO BATTERY POSITIVE SHOULD
BLINK.
DISCONNECT AND CHECK AT VOLTAGE. DOES IT? LEAST TWO INJECTORS
WITH LIGHT
SHOULD BE "OFF" ON ALL
THE INJECTOR TEST LIGHT TERMINALS. J34730-B. IS IT? TESTER SHOULD BLINK WHILE I CRANKING ENGINE.
~ ~ ~ $
DOES IT?
SHORT TO GROUND IN I FAULTY I
OPEN IN INJECTOR II FAUL TV
J CIRCUIT THAT LIGHT ECM DRIVER CIRCUIT(S). ECM WAS "ON".
~ $
• CHECK RESISTANCE OF @ • IGNITION "ON". INJECTORS, SHOULD BE 1.2 -3.0 • TEST LIGHT CONNECTED TO GROUND.
OHMS. • PROBE RED/GRN WIRE AT ANY INJECTOR.
• REPLACE ANY INJECTOR THAT LIGHT SHOULD BE "ON". WAS NOT CORRECT. IS IT? IF ALL WERE OK, REFER TO I CHART A-7 TO TEST FUEL
$ ~
PRESSURE.
• TEST LIGHT CONNECTED TO OPEN IN CIRCUIT BATTERY POSITIVE VOLTAGE BETWEEN INJECTORS PROBE BLUIYEL (DOHC} WIRE OR AND ECM MAIN BLU/YEL, ORG/BLU AND BLU/GRN RELAY. (SOHC) OF ANY INJECTOR.
NOTE LIGHT WHILE CRANKING
THE ENGINE.
LIGHT SHOULD "BLINK".
DOES
IT?
I
$
I
I NO (SOHCll NO (DOHC)j
®
I REFER TO CHART A-7 TO
I
• IGNITION "OFF". TEST FUEL PRESSURE. • DISCONNECT INJECTOR
RESISTOR MODULE.
• USING
DVOM MEASURE RESISTANCE OF THE MODULE BETWEEN THE BLU/YEL WIRE AND THE BLU/GRN WIRE.
SHOULD HAVE 2.7 OHMS ±10%. DOES IT?
$ $
REPAIR OPEN REPLACE INJEC-IN THE INJEC- TOR
RESISTOR
TOR DRIVER MODULE
CIRCUIT(S).