Scan Tool Testing and Procedures

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 650-750
Desired Idle RPM 675
Coolant Temp °C°F Varies 85-105°C (185-220°F)
Intake Air Temp °C°F Varies w/Ambient Temp
Throttle Position Volts 0.33 - 0.46
Throttle Angle Percent (%) 0%
Mass Air Flow Grams/Sec (gm/sec) Approx. 4.9 (varies)
LV8 (Engine Load) Counts 70-80
Oxygen Sensor Millivolts (mV) Varies (100-900)
Rich/Lean Flag Rich or Lean Constantly Changing
Crossover Counts Counts Varying Constantly (0-255)
Air/Fuel Ratio Ratio 14.5-14.8
Spark Advance Degrees Advance 16° (varies)
Fuel Integrator* Counts* 95-140*
Block Learn* Counts* 95-138*
Open/Closed Loop Open/Closed Loop Closed Loop
Block Learn Cell Cell # 0
Knock Retard Degrees 0°
Knock Signal Yes/No No
Idle Air Control Counts 16-20
Park/Neutral P-N/R-DL P-N
Vehicle Speed mph/kph 0
TCC Mode On/Apply/Off Off
TCC Duty Cycle Percent (%) 0%
TCC Slip RPM +254
Purge Duty Cycle Percent Varies
Batt/Ign Volts Volts 13.5-14.2
EGR1 ON/OFF OFF
EGR2 ON/OFF OFF
EGR3 ON/OFF OFF
A/C Request Yes/No No
A/C Clutch On/Off Off
A/C Head Press OK/High Press OK
C/C Brake Switch Applied/Released Released ("Applied" if Cruise Control "ON"/"OFF" switch is "OFF".)
TCC Brake Switch Applied/Released Released
C/C Set Speed mph/kph 0
Desired Servo Position Percent (%) 0%
Actual Servo Position Percent (%) 0%
Cruise Mode Varies 1 of 7 Off
Raw Servo Position Counts Approx. 15-85 and Steady
C/C On/Off Switch On/Off Off
C/C Res/Accel Switch On/Off Off
C/C Set/Coast Switch On/Off Off
C/C Vacuum Solenoid On/Off Off
C/C Vent Solenoid On/Off Off
PRNDL P Hi/Lo Lo
PRNDL A Hi/Lo Lo
PRNDL B Hi/Lo Hi
PRNDL C Hi/Lo Hi
PRNDL Switch PRNDL Position Park
Commanded Gear Commanded Gear 1st
P/N Yes/No Yes
2nd Gear Actual Yes/No No
3rd Gear Actual Yes/No No
4th Gear Actual Yes/No No
Fan Lo On/Off Off (engine temp below 100°C/212°F)
Fan Hi On/Off Off (engine temp below 108°C/226°F)
QDM A High/Low Low
QDM B High/Low Low
Heated W/S Request Yes/No No
VATS Fuel Enable Yes/No Yes
PROM ID PROM # Internal ID Only (this is not the service part number)
Time From Start Minutes


* A Poor PCM ground to the engine, at the ignition module mounting bracket, could cause the "Fuel Integrator" and "Block Learn" values to read around 150 counts. Check this connection carefully and clean if necessary. Also check other engine to chassis and battery ground connections.

If all values are within the specified range, Testing and Inspection.