1992 Isuzu Trooper LS, AutomaticFACTORY OEM SERVICE PROCEDURE

Diagnostic Circuit Check

The Diagnostic Circuit Check will identify a problem created by an Electronic Engine Control System (EECS) malfunction. It is the starting point for diagnosis. This check will direct you to the next logical step in diagnosing the complaint.

After completing Diagnostic Circuit Check and finding on-board diagnostics functioning properly with no trouble codes displayed, use appropriate SCAN DATA table for comparison. The typical values are an average of display values recorded from normally operating vehicles and are intended to represent what a normally functioning system would typically display.

NOTE: Only parameters supplied by manufacturer are used in this article. If a Scan tester reads other parameters, values are not recommended by manufacturer for diagnostic use. A Scan tester displaying faulty data should not be used or a misdiagnosis will occur. Report problem to Scan tester manufacturer.
SCAN DATA

Scan Position (1) Data Value
A/C No (Yes W/A/C Requested)
A/C Clutch Off (On W/A/C Requested)
Air Control Solenoid Off
Battery 13-15 Volts
BARO Voltage Varies Depending On Altitude
BLM (Block Learn Memory) 116-145 Counts
BLE (Block Learn Enable) Yes
BPW (Base Pulse Width) 0-500 Milliseconds
Canister Purge Off
Coolant Temperature 185-221°F (85-105°C)
EGR Solenoid Off
EST (Electronic Spark Timing) Yes
IAC (Idle Air Control) 1-50 Counts
Idle Throttle Yes
INT (Integrator) Varied 108-154 Counts
Knock Retard 0-45 Degrees
MAP (Manifold Absolute Pressure) (2) 1-2 Volts
MAT (Manifold Air Temperature) (3) 50-199°F (10-93°C)
Open/Closed Loop Closed Loop (Open At Idle)
Oxygen Sensor (3) .1-.9 Volts
Power Steering Switch Normal
Prom Identification 0-65535
RPM (4)(5) RPM Is Controlled By ECM
Rich/Lean Flag Varies
Second Throttle Solenoid Off (On above 5000 RPM)
Shift Light Off
Spark Advance Varies
Throttle Angle Zero Percent At Idle
TPS (Throttle Position Sensor) .50-.1.25 Volts
VSS (Vehicle Speed Sensor) 0 MPH
(1) With engine idling at normal operating temperature, in Park or Neutral, system in closed loop and all accessories off.
(2) Voltage varies with vacuum and barometric pressure.
(3) Voltage varies with exhaust temperature.
(4) Plus or minus 50 RPM from desired RPM (A/T).
(5) Plus or minus 100 RPM from desired RPM (M/T).
Fig 1: Diagnostic Circuit Check
G92F26885Courtesy of ISUZU MOTOR CO.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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