GM Service Manual Online
For 1990-2009 cars only

Use the Typical Scan Data Values table only after the Diagnostic System Check-Engine Controls has been completed, no DTCs were noted and you have determined the on-board diagnostics are functioning properly. Scan tool values from a properly running engine may be used for comparison with the engine you are diagnosing. The Typical Scan Data values represent values that would be seen on a normally running engine.

Important:: A scan tool that displays faulty data should not be used, and the problem should be reported to the scan tool manufacturer. Use of a faulty scan tool can result in misdiagnosis and unnecessary parts replacement.

Only the parameters listed below are referred to in this service manual for use in diagnosis. For further information on using the scan tool to diagnose the PCM and related sensors, refer to the applicable reference section listed below. If all values are within the typical range described below, refer to Symptoms - Engine Controls . The Typical Scan Data Values table contains all the parameters included in the following data lists arranged in alphabetical order:

    • Engine Data 1--Contains general information regarding fuel delivery, idle air control (IAC) position, heated oxygen sensor (HO2S) 1, HO2S 2, and other basic engine operating conditions.
    • Engine Data 2--Contains general information regarding engine coolant temperature (ECT), intake air temperature (IAT), mass air flow (MAF), manifold absolute pressure (MAP), and other basic engine operating conditions.
    • Exhaust gas recirculation (EGR) Data--Contains information specific to the EGR system. This list displays parameters required to verify proper EGR system operation
    • Evaporative emission (EVAP) Data--Contains information specific to the EVAP control system. Also displays parameters required to verify proper EVAP system operation.
    • Fuel Trim Data--Contains information specific to the fuel trim operation. Also displays parameters required to verify proper fuel trim operation.
    • Misfire Data--Contains information specific to the misfire diagnostics and parameters required to verify proper operation with regard to misfire.
    • Output Driver Data--Contains information specific to output driver circuits. This data monitors circuit status, and circuit history.

For scan tool parameter definitions, refer to Scan Tool Data Definitions .

Important: Use the Typical Scan Data Values only after the following conditions are met:

    • The Diagnostic System Check - Engine Controls has been completed.
    • The engine is idling unless checking a value at a specified RPM.
    • The throttle is closed unless checking a value at a specified RPM.
    • The vehicle is in PARK or NEUTRAL.
    • The vehicle is operating in Closed Loop.
    • The vehicle accessories are turned OFF.

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Engine Idling/Radiator Hose Hot/Closed Throttle/Park or Neutral/Closed Loop/Accessories Off/Brake Pedal Released

3X Crank Sensor

Engine 2

RPM

Varies, Same as Engine Speed

24X Crank Sensor

Engine 2

RPM

Varies, Max 1689

A/C High Side Pressure Sensor

Engine 2

PSI/Volts/kPa

Varies with refrigerant temperature

A/C OFF for WOT

Engine 2

Yes/No

No

A/C Pressure Disable

Engine 2

Yes/No

No

A/C Relay Circuit Status

Output Driver

Fault/OK

OK

A/C Relay Command

Engine 1, Engine 2, EGR, Misfire

On/Off

Off

A/C Request Signal

Engine 2

Yes/No

No

Air/Fuel Ratio

Engine 2, Fuel Trim

Ratio

14.7:1

BARO

Engine 1, EGR, EVAP, Fuel Trim

kPa

98/Varies

CMP Sensor Signal Present

Engine 2

Yes/No

Yes

Crank Request Signal

Engine 2

Yes/No

No

Cruise Control Active

Engine 1

Yes/No

No

Cruise Inhibit Reason

Engine 1

Varies

Vehicle Speed

Cruise Inhibit Signal Circuit Status

Output Driver

Fault/OK

OK

Cruise Inhibit Signal Command

Engine 1

On/Off

On

Current Gear

Engine 1, Engine 2, EGR, Fuel Trim

1/2/3/4

1

Cycles of Misfire Data

Misfire

Counts

Varies

Cylinder 1 Injector Circuit Status

Output Driver

Fault/OK

OK

Cylinder 2 Injector Circuit Status

Output Driver

Fault/OK

OK

Cylinder 3 Injector Circuit Status

Output Driver

Fault/OK

OK

Cylinder 4 Injector Circuit Status

Output Driver

Fault/OK

OK

Cylinder 5 Injector Circuit Status

Output Driver

Fault/OK

OK

Cylinder 6 Injector Circuit Status

Output Driver

Fault/OK

OK

Cylinder 1 Injector Circuit History

Output Driver

Fault/OK

OK

Cylinder 2 Injector Circuit History

Output Driver

Fault/OK

OK

Cylinder 3 Injector Circuit History

Output Driver

Fault/OK

OK

Cylinder 4 Injector Circuit History

Output Driver

Fault/OK

OK

Cylinder 5 Injector Circuit History

Output Driver

Fault/OK

OK

Cylinder 6 Injector Circuit History

Output Driver

Fault/OK

OK

Decel. Fuel Cutoff

EGR, Fuel Trim

Active/Inactive

Inactive

Desired EGR Position

Engine 1, EGR, Misfire

Volts

0 Volts

Desired Idle Speed

Engine 1, Engine 2, EVAP

RPM

Within 50 RPM of actual engine speed

Driver Module 1 Status

Output Driver

Enabled/Disabled

Enabled

Driver Module 2 Status

Output Driver

Enabled/Disabled

Enabled

Driver Module 3 Status

Output Driver

Enabled/Disabled

Enabled

Driver Module 4 Status

Output Driver

Enabled/Disabled

Enabled

ECT Sensor

Engine 1, Engine 2, EGR, EVAP, Fuel Trim, Misfire

°C /°F

Varies with engine temperature

EGR Flow Test Count

EGR

Count

0

EGR Learned Minimum Position

EGR

Volts

0.68 Volts

EGR Position Sensor

Engine 1, EGR, Misfire

%/Volts

0%/0 Volts

EGR Position Variance

EGR

%

0%

EGR Solenoid Command

EGR

%

0%

Engine Load

Engine 1, Engine 2, EGR, EVAP, Fuel Trim, Misfire

%

21%

Engine Oil Level Switch

Engine 2

OK/Low

OK

Engine Oil Life Remaining

Engine 2

%

Varies

Engine Oil Pressure Switch

Engine 2

OK/Not OK

OK

Engine Run Time

Engine 1, Engine 2, EGR, EVAP, Fuel Trim, Misfire

Hr:min:sec

Varies

Engine Speed

Engine 1, Engine 2, EGR, EVAP, Fuel Trim, Misfire

RPM

Within 50 RPM of actual engine speed

EVAP Fault History

EVAP

No Test Result

--

EVAP Purge Solenoid Circuit Status

Output Driver

Fault/OK

OK

EVAP Purge Solenoid Command

Engine 1, EVAP, Fuel Trim

%

19%

EVAP Vent Solenoid Circuit Status

Output Driver

Fault/OK

OK

EVAP Vent Solenoid Command

Engine 1, EVAP, Fuel Trim

Venting/Not Venting

Venting

FC Relay 1 Circuit Status

Output Driver

Fault/OK

OK

FC Relay 1 Command

Engine 2

On/Off

Off

FC Relay 2 and 3 Circuit Status

Output Driver

Fault/OK

OK

FC Relay 2 and 3 Command

Engine 2

ON/Off

Off

Fuel Level Sensor

EVAP

Volts

0.8 Volts at empty to 2.5 Volts at full

Fuel Pump Relay Circuit Status

Output Driver

Fault/OK

OK

Fuel Pump Relay Circuit History Status

Output Driver

Fault/OK

OK

Fuel Pump Relay Command

Engine 1

On/Off

On

Fuel Tank Level Remaining

EVAP

%

Varies

Fuel Tank Pressure Sensor

Engine 1, EVAP

in H2O/mm Hg/Volts-EVAP only

Varies

Fuel Trim Cell

Engine 1, EVAP, Fuel Trim

Cell #

Varies

Fuel Trim Learn

Engine 1, EVAP, Fuel Trim

Enabled/Disabled

Enabled

Gen L-Terminal Signal Command

Engine 2

On/Off

On

HO2S 1

Engine 1, EVAP, Fuel Trim

mV

0-1132

HO2S 2

Engine 1, Fuel Trim

mV

0-1132

HO2S 1 Heater Command

Fuel Trim

On/Off

On

IAC Position

Engine 1, EGR, Fuel Trim

Counts

15

IAT Sensor

Engine 1, Engine 2, EGR, EVAP, Fuel Trim,

°C/°F

Varies with ambient temperature

Ignition 1 Signal

Engine 1, Engine 2, EGR, EVAP, Fuel Trim,

Volts

13.3 Volts

Ignition Mode

Engine 2

Bypass/IC

IC

IMS

Engine 1

Park, Reverse, Neutral, Drive 4-3-2-1

Park

Injector PWM

Engine 2, Fuel Trim, Misfire

ms

2.90 ms

Knock Retard

Engine 1, EGR

Degrees

0

Long Term FT

Engine 1, Engine 2, EVAP, Fuel Trim,

%

-3

Loop Status

Engine 1, Engine 2, EGR, EVAP, Fuel Trim

Open/Closed

Closed

MAF Sensor

Engine 1, Engine 2, EGR, EVAP, Fuel Trim, Misfire

g/s=Engine 1, EGR, EVAP, FT, Misfire

Hz=Engine 1, Engine 2

4.25 g/s/2210 Hz

MAP Sensor

Engine 1, Engine 2, EGR, EVAP, Fuel Trim, Misfire

kPa/Volts-Engine1, 2 only

38 kPa/1.45 Volts

MIL Circuit Status

Output Driver

Fault/OK

OK

MIL Command

Engine 2

On/Off

Off

Misfire Current Cyl. #1

Misfire

0-198 Counts

0

Misfire Current Cyl. #2

Misfire

0-198 Counts

0

Misfire Current Cyl. #3

Misfire

0-198 Counts

0

Misfire Current Cyl. #4

Misfire

0-198 Counts

0

Misfire Current Cyl. #5

Misfire

0-198 Counts

0

Misfire Current Cyl. #6

Misfire

0-198 Counts

0

Misfire History Cyl. #1

Misfire

0-65535 Counts

0

Misfire History Cyl. #2

Misfire

0-65535 Counts

0

Misfire History Cyl. #3

Misfire

0-65535 Counts

0

Misfire History Cyl. #4

Misfire

0-65535 Counts

0

Misfire History Cyl. #5

Misfire

0-65535 Counts

0

Misfire History Cyl. #6

Misfire

0-65535 Counts

0

Number of DTCs

Engine 1, EVAP, Fuel Trim

#

0

O2 Heater Current

Fuel Trim

Amps

0.54 Amps

PCM / VCM in VTD Fail Enable

Engine 1

Yes/No

No

PCM Reset

Engine 1, Engine 2, EGR, EVAP, Fuel Trim, Output Driver

Yes/No

No

Power Enrichment

Engine 2, Misfire

Active/Inactive

Inactive

Short Term FT

Engine 1, Engine 2, EVAP, Fuel Trim

%

0%

Spark

Engine 1, Engine 2, Fuel Trim, Misfire,

Degrees

20

Start Up ECT

Engine 2, EVAP, Fuel Trim

°C/°F

varies

Start Up IAT

Engine 2, EVAP, Fuel Trim

°C/°F

varies

Starter Enable Relay Circuit Status

Output Driver

Fault/OK/Invalid State

OK

Starter Relay Command

Engine 2

On/Off

Off

TCC Brake Pedal Switch

Engine 1, Engine 2

Applied/Released

Released

TCC PWM Solenoid Command

Engine 2, Misfire

On/Off

Off

TFP Sw

Engine 2, EGR, Fuel Trim

Park/Reverse/Neutral/Drive 4/Drive 3/Drive 2/Drive 1

Drive 2

Torque Delivered Signal

Engine 2

%

86%

Torque Request Signal

Engine 2

%

100%

TP Sensor

Engine 1, Engine 2, EGR, EVAP, Fuel Trim, Misfire,

Volts/%

0.65 Volt/0%

Traction Control Status

Engine 2

Active/Inactive

Inactive

Vehicle Speed Sensor

Engine 1, Engine 2, EGR, EVAP, Fuel Trim, Misfire,

mph/km/h

0

VTD Auto Learn Timer

Engine 1

Active/Inactive

Inactive

VTD Fuel Disable

Engine 1

Active/Inactive

Inactive

VTD Fuel Disable Until Ign. OFF

Engine 1

Yes/No

No