For 1990-2009 cars

Table 1: | Scan Tool Data - Engine Data 1
Table 2: | Scan Tool Data - Engine Data 2
Table 3: | Scan Tool Data - Specific Engine - EGR/EVAP
Table 4: | Scan Tool Data - Specific Engine - Misfire Data
Table 5: | Scan Tool Data - Specific Engine - O2S Data
Table 6: | Scan Tool Data - DTC, Freeze Frame/Failure Records Data
Table 7: | Cat Mon Engine Data

### On Board Diagnostic (OBD) System Check

The Powertrain OBD System Check is an organized approach to identifying a problem that is created by an electronic engine control system malfunction. The OBD system check is the starting point for any driveability complaint diagnosis. This directs the service technician to the next logical step in diagnosing the complaint. Keep the following special considerations in mind while making the OBD system check :

#### Blocking Drive Wheels

Block the vehicle drive wheels and set the emergency brake while checking the system.

#### Cold Oxygen Sensor (O2S 1)

On certain engines, the Oxygen Sensor (O2S 1) may cool down after only a short period of operation at idle. This may cause the system to go into an Open Loop operation. Run the engine at part throttle several minutes and accelerate the engine from idle to part throttle a few times in order to restore a Closed Loop operation.

Notice: Do not use a scan tool that displays faulty data. Report the scan tool problem to the manufacturer. Use of a faulty scan tool can result in misdiagnosis and unnecessary parts replacement.

Only the parameters listed below are used in this manual for diagnosis. If a scan tool reads other parameters, General Motors does not recommend these values for use in the diagnosis. For more description on the values and use of the scan tool to diagnose the PCM inputs, refer to the applicable diagnostic section. If all of the values are within the illustrated ranges, refer to Symptoms.

#### Scan Tool Data - Engine Data 1

At Idle/Upper Radiator/Closed Throttle/Park or Neutral/Closed Loop/Acc. OFF
Scan Tool Parameter | Units Displayed | Typical Data Value
Engine Speed | RPM | ±100 RPM from the desired RPM
Desired Idle Speed | RPM | PCM idle command (varies with calibration)
ECT | °C-°F | 85°-115°C (185°-239°F) (varies with the coolant temperature)
IAT | °C-°F | 10°-80°C (50°-176°F) (varies with under hood temperature)
MAP | kPa | 25-35 kPa
MAP | V | 1-3 volts (varies with the vacuum and the BARO pressure)
BARO | kPa | 65-104 (varies with the altitude and the BARO pressure)
TP Sensor | Volts | 0.200-0.900V (up to 5.0 at wide open throttle)
TP Angle | % | 0% (up to 100% at wide open throttle)
O2S 1 | mV | 1-1000 and varying
HO2S Sensor 2 | mV | 1-1000 and varying
Fuel Trim Cell | Cell Number | 18-21 at idle (varies with the air flow, RPM, P/N, and A/C)
Fuel Trim Index | % | 58-198 (varies) (100% to 100%) (varies)
Short Term FT | % | 58-198 (varies) (-100% to 100%) (varies)
Long Term FT | % | 58-198 (varies) (-100% to 100%) (varies)
Short Term FT Average | % | 58-198 (varies) (-100% to 100%) (varies)
Long Term FT Average | % | 58-198 (varies) (-100% to 100%) (varies)
Spark | Degrees | Varies
Adaptive Knock Retard | Degrees | 0
Knock Retard | Degrees | 0
KS Noise Channel | # | Increments when knock is present
Med. Resolution Resync | 0-255 Counts | 0
CKP Active Counter (7x Reference) | 0-255 Counts | 0-255 - Increments while cranking or running
CMP Active Counter | 0-255 Counts | 0-255 - Increments while cranking or running
Med. Resolution Engine | Yes/No | Yes
CMP Resync Counter | 0-255 Counts | 0
Purge Learned Memory | Counts | 1.00
EVAP Canister Purge | % | 0-100%
IAC Position | Counts | 5-60
Transmission Range | Transmission State | Park/Neutral
Vehicle Speed | Km/h/MPH | 0
FC Relay 1 | On/Off | Off (Varies with Fan Request)
Ignition 1 | Volts | 12.0-15.0V
Loop Status | Open/Closed | Closed
Generator PWM | % | 0-100% (varies)
Generator L Terminal | Active/Inactive | Inactive
Power Enrichment | Active/Inactive | Inactive
TCC Brake Switch | Open/Closed | Closed with brake depressed
Calc. Air Flow | g/s | Varies
Engine LOAD (2.4L) | % | 11-21% (16-29% @ 2500 RPM)
Engine LOAD (2.2L) | % | 22-26% (19-25% @ 2500 RPM)
Number of Current DTCs | # | 0
Engine Run Time | Minutes/Seconds | Varies (since start up)

#### Scan Tool Data - Engine Data 2

At Idle/Upper Radiator/Closed Throttle/Park or Neutral/Closed Loop/Acc. OFF
Scan Tool Parameter | Units Displayed | Typical Data Value
--- | --- | ---
Engine Speed | RPM | ±100 RPM from the desired RPM
Desired Idle Speed | RPM | PCM idle command (varies with calibration)
ECT | °C-°F | 85°-115°C (185°-239°F) (varies with the coolant temperature)
IAT | °C-°F | 10°- 80°C (50°- 176°F) (varies with under hood temperature)
MAP | kPa | 25-35 kPa
MAP | V | 1-3 volts (varies with the vacuum and the BARO pressure)
BARO | kPa | 65-104 (varies with the altitude and the BARO pressure)
TP Sensor | Volts | 0.200-0.900V (up to 5.0 at wide open throttle)
TP Angle | % | 0% (up to 100% at wide open throttle)
Total Misfire Current Counter | 0-255 Counts | 0 (increases with misfires)
Air Fuel Ratio | Ratio | 14.6:1 (varies)
Base PWM Cyl. 1 | mS | 1-4 varies
Base PWM Cyl. 2 | mS | 1-4 varies
Base PWM Cyl. 3 | mS | 1-4 varies
Base PWM Cyl. 4 | mS | 1-4 varies
Engine Oil Level | OK/Low | OK (Low with the low oil level)
ECL | OK/Low | OK (Low with low oil pressure)
A/C Request | Yes/No | No
A/C Relay | Off/On | Off (On with the A/C request)
A/C High Side Pressure | Volts | 0-5.0 Volts
A/C High Side Pressure | psi/kPa | 0-450 PSI (varies with the refrigerant pressure)
FC Relay 1 | Off/On | Off (Varies with fan reqeust)
Stepper Cruise Motor | Enabled/Disabled | Disabled
Cruise | Engaged/Disengaged | Disengaged
TR Switch (P) | Low/High | Low (Auto trans only) (Park only)
TR Switch (A) | Low/High | Low (Auto trans only) (Park only)
TR Switch (B) | Low/High | High (Auto trans only) (Park only)
TR Switch (C) | Low/High | High (Auto trans only) (Park only)
Transmission Range | Invalid/Low/Drive 2/Drive 3/Overdrive/Reverse/Park/Neutral | Park/Neutral (Auto trans only)
Vehicle Speed | MPH and km/h | 0 MPH/km/h
Output Driver 1 Open | 00000000 | 00000000 (A 1 appears with a short to ground or open)
Output Driver 1 Short | 00000000 | 00000000 (A 1 appears with a short to voltage)
Output Driver 2 Open | 00000000 | 00000000 (A 1 appears with a short to ground or open)
Output Driver 2 Short | 00000000 | 00000000 (A 1 appears with a short to voltage)
Number of current DTCs | # | 0
Engine Run Time | Minutes/Seconds | Varies (since start up)

#### Scan Tool Data - Specific Engine - EGR/EVAP

At Idle/Upper Radiator/Closed Throttle/Park or Neutral/Closed Loop/Acc. OFF
Scan Tool Parameter | Units Displayed | Typical Data Value
--- | --- | ---
Engine Speed | RPM | ±100 RPM from the desired RPM
Desired Idle Speed | RPM | PCM idle command (varies with the calibration)
ECT | °C-°F | 85°-115°C (185°-239°F) (varies with the coolant temperature)
IAT | °C-°F | 10°-80°C (50°-176°F) (varies with the underhood temperature)
MAP | kPa | 25-35 kPa
MAP | V | 1-3 volts (varies with the vacuum and the BARO pressure)
BARO | kPa | 65-104 (varies with the altitude and the BARO pressure)
TP Sensor | Volts | 0.200-0.900V (up to 5.0 at wide open throttle)
TP Angle | % | 0% (up to 100% at wide open throttle)
O2S 1 | mV | 1-1000 and varying
HO2S 2 | mV | 1-1000 and varying
IAC Position | Counts (steps) | 5-60 counts
Fuel Trim Cell | Cell number | 18-21 at idle (varies with the air flow, RPM, P/N, an A/C)
Short Term FT | Counts, % | 58-198 (varies) -100% to 100% (varies)
Long Term FT | Counts, % | 58-198 (varies) -100% to 100% (varies)
EGR Delta MAP Calc. | kPa | 0 or a negative number
EGR Decel Filter | kPa | -3 or-4
Desired EGR Position | % | 0%
Actual EGR Position | % | 0%
EGR Flow test Count | # of Samples | --
Purge Learned Memory | Counts | 0
EVAP Canister Purge | % | 0-100%
EVAP Vent Sol. | Open/Closed | Open
Fuel Tank Pressure | Inches of H2O | Depends on Pressure/Vacuum
Fuel Level | % | 0-100% Depends on level
Loop Status | Open/Closed | Closed
Number of current DTCs | # | 0
Engine Run Time | Minutes/Seconds | 0

#### Scan Tool Data - Specific Engine - Misfire Data

At Idle/Upper Radiator/Closed Throttle/Park or Neutral/Closed Loop/Acc. OFF
Scan Tool Parameter | Units Displayed | Typical Data Value
--- | --- | ---
Engine Speed | RPM | ±100 RPM from the desired RPM
Desired Idle Speed | RPM | PCM idle command (varies with calibration)
ECT | °C -°F | 85°-115°C (185°-239°F) (varies with the coolant temperature)
IAT | °C-°F | 10°-80°C (50°-176°F) (varies with under hood temperature)
MAP | kPa | 25-35 kPa
MAP | V | 1-3 volts (varies with the vacuum and the BARO pressure)
BARO | kPa | 65-104 (varies with the altitude and the BARO pressure)
TP Sensor | Volts | 0.200-0.900V (up to 5.0 at wide open throttle)
TP Angle | % | 0% (up to 100% at wide open throttle)
Misfire Current Cyl. #1 | 0-255 Counts | 0 (increase with a misfire)
Misfire History Cyl. #1 | 0-255 Counts | 0 (increase with a misfire)
Misfire Current Cyl. #2 | 0-255 Counts | 0 (increase with a misfire)
Misfire History Cyl. #2 | 0-255 Counts | 0 (increase with a misfire)
Misfire Current Cyl. #3 | 0-255 Counts | 0 (increase with a misfire)
Misfire History Cyl. #3 | 0-255 Counts | 0 (increase with a misfire)
Misfire Current Cyl. #4 | 0-255 Counts | 0 (increase with a misfire)
Misfire History Cyl. #4 | 0-255 Counts | 0 (increase with a misfire)
Total Misfire Current Count | 0-255 Counts | 0 (increase with a misfire)
Base PWM Cyl. 1 | mS | 1-4 varies
Base PWM Cyl. 2 | mS | 1-4 varies
Base PWM Cyl. 3 | mS | 1-4 varies
Base PWM Cyl. 4 | mS | 1-4 varies
Calc. Air Flow | g/s | Varies
LOAD | % | 11-21% (16-29% @ 2500 RPM)
Number of current DTCs | # | 0
Engine Run Time | Minutes/Seconds | Varies (since start up)

#### Scan Tool Data - Specific Engine - O2S Data

At Idle/Upper Radiator/Closed Throttle/Park or Neutral/Closed Loop/Acc. OFF
Scan Tool Parameter | Units Displayed | Typical Data Value
--- | --- | ---
O2S 1 | mV | 1-1000 and varying
HO2S 2 | mV | 1-1000 and varying
Engine Speed | RPM | ±100 RPM from the desired RPM
Desired Idle Speed | RPM | PCM idle Command (varies with calibration)
ECT | °C-°F | 85°-115°C (185°-239°F) (varies with the coolant temperature)
IAT | °C-°F | 10°-80°C (50°-176°F) (varies with the underhood temperature)
MAP | kPa | 25-35 kPa
MAP | V | 1-3 volts (varies with the vacuum and the BARO pressure)
BARO | kPa | 65-104 (varies with the altitude and the BARO pressure)
TP Sensor | Volts | 0.200-0.900V (up to 5.0 at wide open throttle)
TP Angle | % | 0% (up to 100% at wide open throttle)
Fuel Trim Cell | Cell # | 18-21 at idle (varies with air flow, RPM, P/N, an A/C)
Fuel Trim Index | Counts, % | 8-198 (varies) 100% to 100% (varies)
Short Term FT | Counts, % | 58-198 (varies) 100% to 100% (varies)
Long Term FT | Counts, % | 8-198 (varies) 100% to 100% (varies)
Short Term FT Average | Counts, % | 8-198 (varies) 100% to 100% (varies)
Long Term FT Average | Counts, % | 8-198 (varies) 100% to 100% (varies)
Lean/Rich Transition | 0-255 Counts | 0
Rich/Lean Transition | 0-255 Counts | 0
Lean/Rich Average Time | mS | 0
Rich/Lean Average Time | mS | 0
Rich/Lean TO Lean/Rich Ratio Sensor1 | Ratio | Varies
Calc. Air Flow | g/s | Varies
Engine LOAD ( 2.4L) | % | 11-21% (16-29% @ 2500 RPM)
Engine LOAD ( 2.2L) | % | 22-26% (19-25% @ 2500 RPM)
Loop Status | Open/Closed | Closed
Number of Current DTCs | # | 0
Engine Run Time | Minutes/Seconds | Varies (since start up)

#### Scan Tool Data - DTC, Freeze Frame/Failure Records Data

At Idle/Upper Radiator/Closed Throttle/Park or Neutral/Closed Loop/Acc. OFF
Scan Tool Parameter | Units Displayed | Typical Data Value
--- | --- | ---
DTC Freeze Frame | # | DTC #
Scan Tool Parameter | Units Displayed | Typical Data Value
Air/Fuel Ratio | Ratio | Varies
Calc. Air Flow | g/S | Varies
ECT | °C-°F | Varies
BARO | kPa, V | Varies
Base PWM Cyl. 1 | mS | Varies
MAP | kPa, V | Varies
Short Term FT | Counts, % | Varies
Long Term FT | Counts, % | Varies
Loop Status | Open/Closed | Varies
MPH | MPH and km/h | Varies
Load (2.4L Engine) | % | 15-21% (16-29% @ 2500 RPM)
Load (2.2L Engine) | % | 22-26% (19-25% @ 2500 RPM)
TP Angle | % | Varies
Engine Speed | RPM | Varies
Mileage Since First Failure | km | Varies
Mileage Since Last Failure | km | Varies

#### Cat Mon Engine Data

At Idle/Upper Radiator/Closed Throttle/Park or Neutral/Closed Loop/Acc. OFF
Scan Tool Parameter | Units Displayed | Typical Data Value
Engine Speed | RPM | ±100 RPM from the desired RPM
Desired Idle Speed | RPM | PCM idle command (varies with calibration)
ECT | C-F | 85°-115°C (185°-239°F) (varies with the coolant temperature)
IAT | °C°F | 10°-80°C (50-176°F) (varies with under hood temperature)
MAP | kPa | kPa 25-35
MAP | V | 1-3 volts (varies with the vacuum and the BARO pressure)
BARO | kPa | 65-104 (varies with the altitude and the BARO pressure)
TP Sensor | Volts | 0.200-0.900V (up to 5.0 at wide open throttle)
TP Angle | % | 0% (up to 100% at wide open throttle)
Engine Run Time | Seconds | Varies (since start up)
# of Catalyst Mon. Test Completed. | # of Samples | Varies
Loop Status | Open/Closed | Closed
Catalyst Converter TT | °C°F | Varies with engine load
Calc. Air Flow | g/s | Varies
Short Term FT | Counts | 58-198 (varies)
Short Term FT | % | -100 to 100% (varies)
O2S Bank 1 | mV | 1-1000 and varying
HO2S Sensor 2 | mV | 1-1000 and varying