GM Service Manual Online
For 1990-2009 cars only

Use the Typical Scan Data Values table only after the Powertrain On-Board Diagnostic System Check has been completed, no DTC(s) 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 section for diagnosis. The Typical Scan Data Values table contains all the parameters included in the following data lists arranged in alphabetical order:

Engine Data

    • ENG 1- Contains general information regarding fuel delivery and basic engine operating conditions.
    • ENG 2 - Contains general information regarding IC, KS, EVAP, A/C, and basic engine operating conditions.

Specific Engine Data

    • EGR - Contains information specific to the Exhaust Gas Recirculation system flow diagnostics and the EGR valve pintle position sensor diagnostics. Also displays parameters required to verify proper EGR system operation.
    • CATALYST - Contains information specific to the TWC diagnostics and parameters required to verify proper TWC system operation.
    • HO2S - Contains information specific to the Heated Oxygen Sensor diagnostics and parameters required to verify proper HO2S operation.
    • MISFIRE - Contains information specific to the misfire diagnostics and parameters required to verify proper operation with regard to misfire.

Typical Scan Tool Data Values

Scan Tool Parameter

Units Displayed

Typical Data Value

Reference

A/C Off For WOT

Yes/No

No

Powertrain Control Module Controlled Air Conditioning

A/C Refrigerant Pressure

Volts

Varies with refrigerant temperature

Powertrain Control Module Controlled Air Conditioning

A/C Pressure Out Of Range

Yes/No

No (Yes with low or high A/C refrigerant pressure)

Powertrain Control Module Controlled Air Conditioning

A/C Request

Yes/No

No (Yes with A/C ON)

Powertrain Control Module Controlled Air Conditioning

A/C Slugging

Active/Inactive

Inactive

Powertrain Control Module Controlled Air Conditioning

Actual EGR Position

Percent

0%

DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient

Air/Fuel Ratio

Ratio

14.2:1-14.7:1

Fuel Metering Modes of Operation

BARO

kPa

65-110 (Depends on altitude and barometric pressure).

Information Sensors

Commanded A/C

On/Off

Off (On with A/C compressor engaged)

Powertrain Control Module Controlled Air Conditioning

Commanded Fan 1/Commanded Fan 2

On/Off

Off (On with low speed fans running)

Electric Cooling Fan

Commanded Fan 1/Commanded Fan 2

On/Off

Off (On with high speed fans running)

Electric Cooling Fan

Commanded Gen

On/Off

On

Commanded Gen

Commanded TCC

Engaged/Disengaged

Disengaged

4T60-E Automatic Transaxle Diagnosis

Cruise Engaged

Yes/No

No

DTC P1554 Cruise Control Feedback Circuit

Cruise Inhibited

Yes/No

Yes

DTC P1554 Cruise Control Feedback Circuit

Current Gear

1/2/3/4

1

4T60-E Automatic Transaxle Diagnosis

Decel Fuel Mode

Active/Inactive

Inactive

Fuel Metering Modes of Operation

Desired EGR Position

Percent

0%

DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient

Desired Idle

RPM

PCM commanded idle speed (varies with temperature).

DTC P0506 Idle Speed Low

DTC P0507 Idle Speed High

Desired Torque

Percent

80%-95%

Information Sensors

Section 5E2

ECT

°C, °F

85°C-105°C / 185°F-220°F (varies with temperature).

Information Sensors

EGR Closed Valve Pintle Position

Volts

0.14-1.0 volt

DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient

EGR Duty Cycle

Percent

0%

DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient

EGR Feedback

Volts

0.14-1.0 volt

DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient

EGR Position Error

Percent

0%-9%

DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient

EGR Test Count

Counts

0-10

DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient

Engine Load

Percent

2%-5% at idle

7%-10% at 2500 RPM

--

Engine Run Time

Hr: Min: Sec

Depends on time since startup.

--

Engine Speed

RPM

±100 RPM from Desired Idle

Electronic Ignition (EI) System

DTC P1374 Crankshaft Position (CKP) High to Low Resolution Frequency Correlation

EVAP Purge PWM

Percent

0%-25% (varies)

Evaporative Emission Control System

EVAP Vacuum Switch

Purge/No Purge

No Purge (Purge if over 25% EVAP Purge PWM is commanded).

Evaporative Emission Control System

Fuel Pump

On/Off

On

Fuel Pump Electrical Circuit Diagnosis

Fuel Trim Cell

Cell #

0

DTC P0171 Fuel Trim System Lean

Fuel Trim Learn

Disabled/Enabled

Enabled

--

Generator Lamp

On/Off

Off

Powertrain Control Module Controlled Warning Lamps

HO2S Sen. 1

Not Ready/Ready

Ready

DTC P0135 HO2S Heater Performance Sensor 1

HO2S Sen. 1

millivolts

0-1000, constantly varying

Information Sensors

HO2S Sen. 2

mIllivolts

0-1000,varies

Information Sensors

HO2S Warm Up Time

Min: Sec

Depends on startup intake air temperature, startup engine coolant temperature, and time to HO2S activity.

DTC P0135 HO2S Heater Performance Sensor 1

HO2S XCount

Counts

Varies

HO2S Sen. 1

IAC Position

Counts

10-40

DTC P0506 Idle Speed Low

DTC P0507 Idle Speed High

IAT

°C, °F

Varies with ambient air temperature.

Information Sensors

Idle Speed Error

RPM

Less than 100

DTC P0506 Idle Speed Low

DTC P0507 Idle Speed High

Ignition 1

Volts

13 (Varies)

DTC P0560 System Voltage

Ignition Mode

IC/Bypass

IC

Electronic Ignition (EI) System

Injector Pulse Width

milliseconds

1.5-3.5 (Varies with engine load)

--

Knock Retard

Degrees

Knock Sensor (KS) System

KS Activity

Yes/No

No

Knock Sensor (KS) System

KS Minimum Learned Noise

Volts

0.1-3.0 (varies)

Knock Sensor (KS) System

KS Noise Channel

Volts

0.1-3.0 (varies)

Knock Sensor (KS) System

Long Term Fuel Trim

Percent

-10%-10%

DTC P0171 Fuel Trim System Lean

Loop Status

Open/Closed

Closed

Fuel Metering Modes of Operation

Low Oil Lamp

On/Off

Off

Powertrain Control Module Controlled Warning Lamps

MPH / km/h

MPH, Km/h

0

4T60-E Automatic Transaxle Diagnosis

MAF

gm/s

3-6 gm/s at idle

13-16 gm/s at 2500 RPM (Depends on engine load and barometric pressure)

Information Sensors

MAF Frequency

Hz

1200-3000 (Depends on engine load and barometric pressure).

Information Sensors

MAP

kPa/Volts

29-48 kPa / 1-2 Volts (Depends on engine load and barometric pressure).

Information Sensors

MIL

On/Off

Off

Powertrain Control Module Controlled Warning Lamps

Misfire Cur. #1-#6

Counts

0-4

DTC P0300 Engine Misfire Detected

Misfire Failures Since First Fail

Counts

0

DTC P0300 Engine Misfire Detected

Misfire Hist. #1-#6

Counts

0

DTC P0300 Engine Misfire Detected

Misfire Passes Since First Fail

Counts

0

DTC P0300 Engine Misfire Detected

Oil Level

Ok/Low

Ok

Powertrain Control Module Controlled Warning Lamps

Power Enrichment

Active/Inactive

Inactive

Fuel Metering Modes of Operation

Rich/Lean

Rich/Lean

Constantly changing

Fuel Metering Modes of Operation

Short Term Fuel Trim

Percent

-10%-10%

DTC P0171 Fuel Trim System Lean

Spark

Degrees

-20° (varies)

Electronic Ignition (EI) System

Start Up ECT

°C, °F

Depends on engine coolant temperature at time of startup

--

Start Up IAT

°C, °F

Depends on intake air temperature at time of startup

--

TCC Enable

On/Off

Off

4T60-E Transaxle Diagnosis

Throttle at Idle

Yes/No

Yes

DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage

Total Misfire Current Count

Counts

0-5

DTC P0300 Engine Misfire Detected

TP Angle

Percent

0%

DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage

TP Sensor

Volts

0.20-0.74

DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage

Transmission Range

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

Park

Information Sensors

TR P A B C

X/0

0 0 X X

Information Sensors

Trans Hot Mode

Active/Inactive

Inactive

4T60-E Transaxle Diagnosis

TWC Diagnostic

Enabled/Disabled

Enabled

DTC P0420 Catalyst System Low Efficiency

TWC Monitor Test Counter

Counts

0

DTC P0420 Catalyst System Low Efficiency

TWC Protection

Active/Inactive

Inactive

Fuel Metering Modes of Operation

VTD Fuel Disable

Active/Inactive

Inactive

DTC P1626 Theft Deterrent Fuel Enable Signal Lost

DTC P1629 Theft Deterrent Fuel Enable Signal Not Received