Isuzu Trooper four-cylinder engine codes, 1984 thru 1991
Trouble Code Circuit or System / cause Probable cause / Fix / Info
Code 12
(1 flash, pause, 2 flashes)
Diagnostic Mode This code will flash whenever the diagnostic terminal is grounded with the ignition turned on and when the engine is not running. Additional trouble odes are stored in the ECM, and they will be displayed after this code has flashed three times.
Code 13
(1 flash, pause, 3 flashes)
Heated Oxygen sensor circuit The circuit is open or the oxygen sensor is deteriorated. Check wiring, replace sensor if necessary. *
Code 14
(1 flash, pause, 4 flashes) Coolant temperature sensor The signal from the sensor is insufficient or the circuit is shorted to ground. Check wiring, replace sensor if necessary.*
Code 15
(1 flash, pause, 5 flashes)
Coolant Temperature sensor The signal from the sensor is excessive, or the circuit is open. Check wiring, replace sensor if necessary. *
Code 21
(2 flash, pause, 1 flashes) WOT switch System.
Both idle and full contact simultaneously.
Replace TVS/TPS. *, **
Code 43
(4 flash, pause, 3 flashes) WOT switch System Idle makes continuous contact.
Replace TVS/TPS. *, **
Code 65
(6 flash, pause, 5 flashes) WOT switch System
Signal is constant.
Replace TVS/TPS. *, **
Code 22
(2 flash, pause, 2 flashes) Starter Signal System The starter signal circuit is open or shorted.
(1988 and 1989 Troopers).
Code 22
(2 flash, pause, 2 flashes) Fuel cut solenoid circuit The fuel cut solenoit circuit is shorted or open.
(except 1988 and 1989 Troopers).
Code 23
(2 flash, pause, 3 flashes) Mixture Control Solenoid Circuit The mixture control solenoid circuit is open or shorted.
Check the circuit.
(except 1988 and 1989 Troopers)
Code 23
(2 flash, pause, 3 flashes) Power Transistor for Ignition. The power transistor for the ignition system is shorted at the output terminal.
Check the circuit.
(1988 and 1989 Troopers)
Code 35
(3 flash, pause, 5 flashes) Power Transistor for Ignition The circuit is open. Check the wiring.
Code 54
(5 flash, pause, 4 flashes) Power Transistor for Ignition Possible defective transistor in the ECM, or shorted vacuum control solenoid. Dealer service check recomended.
Code 25
(2 flash, pause, 5 flashes) Vacuum switching valve system for fuel pressure control.
Circuit is either open or shorted to ground.
Check circuit.
Code 53
(5 flash, pause, 3 flashes) Vacuum switching valve system for fuel pressure control.
Driver transister in ECM open or faulty vacuum switching valve. Dealer recomended service.
Code 26
(2 flash, pause, 6 flashes) Air vacuum switching valve for the EVAP canister purge system.
Circuit is either open or is shorted to ground.
Check the circuit.
Code 27
(2 flash, pause, 7 flashes) Air vacuum switching valve for the EVAP canister purge system.
Driver transister in ECM is open.
Have the ECM checked by dealer, or service center.
Code 31
(3 flash, pause, 1 flashes) Ignition Signal Ignition cicuit shorted.
Dealer service recomended.
Code 32
(3 flash, pause, 2 flashes) EGR temperature sensor system.
Sensor is faulty or circuit is shorted.
Check circuit, or replace sensor. *
Code 34
(3 flash, pause, 4 flashes) EGR temperature sensor system.
The circuit is shorted.
Check circuit for shorts.
Code 33
(3 flash, pause, 3 flashes) Fuel Injector System.
The fuel injector system is either open or shorted to ground. Check circuit.
Code 64
(6 flash, pause, 4 flashes) Fuel Injector System.
The driver transister in ECM is faulty.
Dealer recomended service.
Code 41
(3 flash, pause, 5 flashes) Crank Angle Sensor Faulty signal or harness open.
Check the wiring or replace the crank angle sensor. *
Code 44
(4 flash, pause, 4 flashes) Fuel Metering System Incorrect signal - low voltage (lean)
Check the oxygen sensor.
Code 45
(4 flash, pause, 5 flashes) Fuel Metering System Incorrect signal - high voltage (rich)
Check the oxygen sensor.
Code 51
(5 flash, pause, 1 flashes) ECM (abnormal LSI-1) The fuel cut solenoid circuit is shorted or the ECM is faulty.
Dealer service recomended.
Code 52
(5 flash, pause, 2 flashes) ECM (abnormal LSI-2) Faulty ECM.
Dealer service recomended.
Code 55
(5 flash, pause, 5 flashes) ECM Faulty A/D converter in ECM.
Dealer service recomended.
Code 61
(6 flash, pause, 1 flashes) Mass Air Flow Sensor Circuit open or shorted to ground, or the hot wire is broken. (insufficient signal)
Check circuit.
Code 62
(6 flash, pause, 2 flashes) Mass Air Flow Sensor Broken Cold wire. (excessive signal)
Check circuit.
Code 63
(6 flash, pause, 3 flashes) Vehicle speed sensor Circuit open or shorted to ground, or the speed sendor is broken.
Check the wiring or replace the sensor. *
* At times, replacing the sensor, switch, or other component may not cure the problem. Seek professional help or advice (or better yet search the net or subscribe to an Isuzu mailing list like
isuzu4x4@moab.off-road.com and ask lots of questions!
** Follow this link to find advice from isuzu list members who have troublshot some of the common problems with TPS/TVS.
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