Powertrain OBD System Check: Notes
NOTE:
DO NOT turn ignition off or clear DTCs during this test unless instructed to do so.
- Check for one or more of these conditions: MIL does not illuminate at any time, MIL blinks or stays on after engine has been started, poor engine performance and/or suspected fault in PCM controlled component exists. If any of these conditions apply, go to next step. If none of these conditions apply, system is okay at this time. Check for intermittent connections.
- Turn ignition switch to RUN position. If MIL illuminates, go to next step. If MIL does not illuminate, repair MIL. See MALFUNCTION INDICATOR LIGHT (MIL) INOPERATIVE .
- Turn ignition switch to LOCK position. Connect scan tool to data link connector. Turn ignition switch to RUN position. If scan tool displays engine data, go to next step. If scan tool does not display engine data, repair data link connection. See DATA LINK CONNECTOR DIAGNOSIS .
- Attempt to start engine. If engine starts, go to next step. If engine does not start, repair no start condition. See BASIC TESTING article.
- Retrieve codes. See RETRIEVING CODES under SELF-DIAGNOSTIC SYSTEM. If no codes were retrieved, go to next step. If codes were retrieved, perform appropriate DTC test under DIAGNOSTIC TROUBLE CODES .
- Start engine. If MIL is not flashing or on steady and no DTCs were retrieved, go to next step. If MIL is flashing or on steady and no DTCs were retrieved, repair MIL. See MALFUNCTION INDICATOR LIGHT (MIL) REMAINS ON .
- Compare scan tool display with data valve. See DATA VALUES table. If scan tool display and data valves are within typical valve range, repair by symptom. See SYMPTOMS in TESTS W/O CODES article. If scan tool display and data valves are not within typical valve range, check scan tool for proper operation by connecting to a known-good vehicle. If scan tool is okay, check wiring for poor connections. If wiring is okay, check appropriate components for proper operation.
DATA VALUES
| Parameter | Units Displayed | Typical Value |
|---|---|---|
| Air Conditioning | On/Off | Off |
| BARO | kPa | 89-99 |
| Battery Voltage | Volts | 14 |
| Charging Efficiency | Precent | Varies Electrical load |
| Closed Throttle Switch | On/Off | On |
| Desired Idle Speed | RPM | 800 |
| ECT | °F (°C) | 176-194 (80-90) |
| EGR By-pass Solenoid | On/Off | Off |
| EGR Solenoid Vacuum Valve | On/Off | Off |
| Engine Load | Percent | 14-24 |
| Engine Speed | RPM | 75-850 |
| EVAP Density Trim | Counts | Varies |
| EVAP Duty Cycle | Percent | 0-100 |
| EVAP Vent Solenoid | On/Off | Off |
| Fuel Cut-Off Signal | Yes/No | No |
| Fuel Level | Precent | Varies With Amount Of Fuel |
| Fuel Pump | On/Off | On |
| Fuel Tank Pressure | mm Hg | Varies |
| Fuel Tank Pressure Control Solenoid | On/Off | Varies |
| HO2S (Sensor 1) | Millivolts | 50-950 |
| HO2S (Sensor 2) | Millivolts | 50-950 |
| HO2S (Sensor 1) | Yes/No | Yes |
| HO2S (Sensor 2) | Yes/No | Varies |
| IAT | °F (°C) | 68-95 (20-35) |
| Injector PWM | Milliseconds | 2.7-4.3 |
| Long Term FT | Counts | 128 |
| Long Term FT | Percent | -16.4-20.8 |
| Loop Status | Open/Closed | Closed |
| MAP (Pressure) | kPa | 29-47 |
| MAP (Voltage) | Volts | 1.32-1.90 |
| MAF | Grams/Second | 2.6-3.1 |
| Mode Selector Switch | Normal/Power | Varies On Selection |
| Monitor TCC Solenoid | On/Off | Off |
| Overdrive Switch | On/Off | Varies On Selection |
| PNP Switch | P/N,D | P/N |
| Power Steering Switch | On/Off | Off (Wheels Straight) |
| Short Term FT | Counts | 128 |
| Short Term FT | Percent | -25-32 |
| Spark | Degrees | 6-10 |
| Spark Advance Adjust Test Switch | Yes/No | No |
| Starter Switch | Release/Cranking | Release |
| TCC Solenoid | On/Off | Off |
| Throttle Position Level (A/T) | Counts | 0 |
| Total Fuel Trim | Percent | -37.3-58.2 |
| Vehicle Speed | km/h/MPH | 0 |