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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 directs you to the next logical step in diagnosing a complaint.

After completing diagnostic circuit check and finding on-board diagnostics functioning properly with no trouble codes displayed, use SCAN DATA table for comparison. The typical values are an average of display values recorded from a properly operating vehicle, and are intended to represent a normal system 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 Clutch Off
A/C Request No
Base Pulse Width (BPW) .8-3.0 Milliseconds
Battery 13.5-14.5 Volts
Block Learn Cell 0
Block Learn Enable No
Block Learn Memory (BLM) 118-138 Counts
Coolant Temperature 185-221°F (85-105°C)
Desired RPM ECM Idle Command
EGR Solenoid Off
EGR Temp. Signal 0-5 Volts
Engine RPM
A/T 890-990 RPM
M/T 800-900 RPM
IAC 1-50 Counts
Idle Throttle No
Integrator (INT) 110-145 Counts
MAP (2) .5-2.0 Volts
MAT Temperature (3) 50-194°F (10-90°C)
Open/Closed Loop Closed Loop (Open w/Extended Idle)
O2 Sensor (4) 100-900 Millivolts
Park/Neutral Switch P/N
Power Steering Switch Normal
Shift Light (M/T) Off
Spark Advance Varies
Throttle Angle (%) 0
TPS .4-1.25 Volts
Vehicle Speed 0
(1) With engine at idle, normal operating temperature, Park or Neutral, system in closed loop and all accessories off.
(2) Depending on vacuum and barometric pressure.
(3) Depending on underhood temperature.
(4) Voltage will continuously vary.
Fig 1: Diagnostic Circuit Check
G90I17945Courtesy of ISUZU MOTOR CO.