To avoid damage to the ecm/pcm or other ignition system components, do not use electrical test equipment such as battery or AC-powered voltmeter, ohmmeter, etc. or any type of tester other than specified.
The Assembly Line Diagnostic Link (aldl) connector is used for communicating with the ecm. It is usually located under the instrument panel and is sometimes covered by a plastic cover labeled `diagnostic connector.' Codes stored in the ecm's memory can be read through a handheld diagnostic scanner plugged into the aldl connector. If a scanner is not available, the codes can also be read by jumping from terminal A to B of the aldl connector and counting the number of flashes of the Service Engine Soon light, with the ignition switch turned on .
To clear codes from the ecm memory, the ecm power feed must be disconnected for at least 30 seconds. Depending on the vehicle, the ecm power feed can be disconnected at the positive battery terminal pigtail, the inline fuseholder that originates at the positive connection at the battery or the ecm fuse in the fuse block. The negative battery cable may also be disconnected; however, other on-board memory data, such as preset radio tuning, will also be lost.
Also, if battery power is lost, computer relearn time is approximately 5-10 minutes. This means the computer may have to re-calibrate components which set up the idle speed and the idle may fluctuate while this is occurring.
IGNITION SYSTEM CHECK
- Check for codes. If any are found, refer to the appropriate chart in .
- Turn the ignition switch on. Verify that the Service Engine Soon light is on.
- Install the scan tool and check the following:
Throttle Position Sensor (tps)-if over 2.5 volts, at closed throttle, check the tps and circuit.
Coolant Sensor-if not between -30°C and 130dgC, checks the coolant temperature sensor and circuit.
- Disconnect all injector connectors and install injector test light (J-34730-2 or equivalent) in injector harness connector. Test light should be off.
Perform this test on 1 injector from each bank.
- Connect spark checker, (J-26792 or equivalent), and check for spark while cranking. Check at least 2 wires.
- If spark occurs, reconnect the spark plug wires and check for fuel spray at the injector(s) while cranking.
- If no spark occurs, check for battery voltage to the ignition system through the ign fuse. If ok, substitute known good parts for possible faulty ignition parts. If this is not feasible, refer to the `C-4" charts for your engine application in .