Electrical Component Resistance

Note: Isuzu does not provide code driven diagnostic charts for this model, but rather provides diagnosis for the system in the figure above. Additionally, there are component tests and symptom test as described below.



INSPECT DG TERMINAL VOLTAGE


1. INSPECT THROTTLE POSITION SENSOR SIGNAL





1) Turn the ignition switch to ON. Do not start the engine.
2) Connect a voltmeter to the DG terminal and body ground.





3) While slowly depressing the accelerator pedal, check that DC terminal voltage rises in sequence.


- If the voltage does not change in proportion to the throttle opening angle, there is a malfunction in the throttle position sensor or circuit.



2. INSPECT BRAKE SIGNAL






1) Depress the accelerator pedal until the DG terminal indicates 8V.
2) Depress the brake pedal and check the voltage reading from the DG terminal.

Brake pedal depressed 0v

Brake pedal released 8V


- If not as indicated, there is a malfunction in either the stop light switch or circuit.


3. INSPECT EACH UP SHIFT POSITION






1) Warm up the engine.

Coolant temperature : 80°C (176°F)

2) Turn the O/D switch to "ON".
3) Place the pattern select switch in "Normal" and the shift selector into the "D" range.
4) During a road test (above 10 km/h or 6 mph) check that voltage at the DG terminal is as indicated below for each up-shift position.
5) If the voltage rises from OV to 7V in the sequence shown, the control system is okay.





6) Take the voltage reading when the vehicle speed is 10 km/h (6 mph) or more. The chart above shows the voltmeter reading and corresponding gears.

Note: Determine the gear position by a light shock or change in engine rpm when shifting. The lock-up clutch will turn ON only infrequently during normal 2nd and 3rd gear operation. To trigger this action, press the accelerator pedal to 50% or more of its stroke. At less than 50%, the voltage may change in the sequence 2V - 4V - 6V - 7V.

SYMPTOM DIAGNOSIS





O/D Light Blinks While Driving









No Shifting





Shift Point too High or too Low




No up-shift to O/D (After warm up)




No Lock-up (After Warm up)




Transfer Gear No Change 4L from 4H






INSPECTION OF ELECTRONIC CONTROL COMPONENTS


INSPECT VOLTAGE OF ECT COMPUTER CONNECTOR






1) Turn on the ignition switch.









2) Measure the voltage at each terminal.












INSPECT NEUTRAL START SWITCH


INSPECT BRAKE SIGNAL





- Check that the brake light comes on when the brake pedal is depressed.



INSPECT NO.1 SPEED SENSOR





- Check that there is continuity between the bolts four times per each revolution of the shaft.
- It continuity is not as specified, replace the speedometer.


Location: The speed sensor is installed in the speedometer assembly.



INSPECT NO.2 SPEED SENSOR





1) Remove No.2 speed sensor.
2) Connect an ohmmeter between the terminals.
3) Bring a magnet close to then away from the sensor tip and check that the meter needle deflects from 0 ohms to infinite ohms.






INSPECT PATTERN SELECTION SWITCH





INSPECT O/D OFF SWITCH





INSPECT TRANSFER POSITION SWITCH






INSPECT TRANSMISSION AND TRANSFER FLUID THERMO SENSOR





INSPECTION OF SOLENOID



INSPECT THROTTLE POSITION SENSOR





1) Turn the starter switch to the "ON" position.
2) Remove the water shield cover as shown in the illustration. Do not remove the connector.
3) Place the circuit tester positive probe in the white color harness.






Note: The throttle position sensor has three leads, red for 5V power source, white for output, and black for GND.

4) Measure the voltage between black color harness.

Note: Make sure that 5V (+/- O.5V) is measured at the red color harness before measurement at step 4).








5) Confirm that difference in voltage of idle position and full position is 3.6 +/- 1v.