Scan Tool Data Definitions

The "SCAN" data values, listed below, are typical for the test parameters of a "TECH-1" or equivalent "scan" tool connected to the ALDL diagnostic connector, and under the following conditions:

Engine running at idle/closed throttle.
Engine at normal operating temperature.
System operating in "closed-loop".
Accessories "OFF".
Brake NOT applied.

Many of the parameters show "data" rather than voltage or resistance values, and cannot be read using a volt/ohm meter.


PARAMETER UNITS TYPICAL VALUE

Engine Speed RPM ± 100 RPM from desired idle
Desired Idle RPM Varies W/temperature
Coolant Temp °C/°F Varies 85-109°C (185-223°F)
Intake Air Temp °C/°F Varies W/Under hood temperature 10-90°C (50-195°F)
MAP kPa/Volts 29 - 48 kPa/1 - 2 volts) Depending on manifold and barometric pressure
Purge Duty Cycle Percent 0%
Throttle Position Volts 0.29 - 0.59
Throttle Angle Percent (%) 0%
Oxygen Sensors Millivolts (mV) Varies (100-900)
Open/Closed Loop Open/Closed Loop Closed Loop
Left and Right Fuel Integrator Counts varies
(Short Term Fuel Trim)

Left and Right Block Learn Counts 118 - 138
(Long Term Fuel Trim)

Block Learn Cell Cell # 4
Block Learn Enable Yes/No No
(Fuel Trim Enable)

Spark Advance Degrees Advance Varies (ECM Controlled)
Vehicle Speed MPH/KPH 0
Knock Retard Degrees 0°
Knock Signal Yes/No No
Batt/Ign Volts Volts 12.5-14.5
Fuel Pump Volts Volts 12.5-14.5
EGR Desired Position Percent (0-100%) Varies
EGR Actual Position Percent (0-100%) Varies
EGR Pintle Position Volts (0.00-5.10V) Varies
EGR Duty Cycle Percent (0-100%) Varies


Idle Air Control Counts 1 - 40
Fan 1, Fan 2 On/Off Off (coolant temperature below 109°C/226°F)
A/C Fan Request Yes/No No (Yes with A/C high pressure)
A/C Request Yes/No No (Yes with A/C requested)
A/C Clutch On/Off Off (On with A/C turned on - cycles)
A.I.R. Pump Relay On/Off Off
A.I.R. Control Divert/Port Divert
1-4 Shift Active Yes/No No
Oil Temperature °C/°F Varies 85-95°C (185-203°F) depending on oil temperature
Secondary Vacuum kPa/Volts 0/.56
Power Switch Normal/Full Depends on position of switch
Secondary System On/Off Off
Injector Pulse Width Milliseconds 1-4 (varies)
ASR Control Yes/No No
FEDS/Pass Key (GM trademark) OK/Not OK OK
Port Throttle Solenoid On/Off Off
PROM ID 0 - 9999 Internal ID Only (this is not the service part number)
Time From Start Hrs/Min Varies