| 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.
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 | Yes/No | No |
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 |
PNP | P-N, R-D-L | P-N |
Vehicle Speed | Km/h/MPH | 0 |
Ignition 1 | Volts | 12.0-15.0V |
Loop Status | Open/Closed | Closed |
TCC Brake Switch | Open/Closed | Closed with brake depressed |
Calc. Air Flow | g/s | Varies |
Engine LOAD | % | 22-26% (19-25% @ 2500 RPM) |
Number of Current DTCs | # | 0 |
Engine Run Time | Seconds | Varies (since start up) |
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 |
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) |
Stepper Cruise Motor | Enabled/Disabled | Disabled |
Cruise | Engaged/Disengaged | Disgaged |
PNP | 0=R/DL, 1=P/N | 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 | Seconds | Varies (since start up) |
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 Sensor 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 | Seconds | 0 |
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 |
Engine LOAD | % | 11-21% (16-29% @ 2500 RPM) |
Number of current DTCs | # | 0 |
Engine Run Time | Seconds | Varies (since start up) |
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 | % | 22-26% (19-25% @ 2500 RPM) |
Loop Status | Open/Closed | Closed |
Number of Current DTCs | # | 0 |
Engine Run Time | Seconds | Varies (since start up) |
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 |
Engine Load | % | 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 |
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 |
