Diagnostic Notes

BEFORE STARTING

1. Verify the customer complaint and locate the correct symptoms.


2. Several of the symptom procedures call for a careful visual check. The importance of this step cannot be stressed too strongly - it can lead to correcting a problem without further checks and can save valuable time.
Visually Inspect:
Vacuum hoses for splits, kinks, and proper connections, as shown on Emission Control Information label.
Air leaks at throttle valve mounting, common chamber mounting and intake manifold.
Ignition wires for cracking, harness, proper routing, and carbon tracking.
Wiring for proper connections, pinches, and cuts.

3. Be careful when checking the system components (Closed Loop Emission Control System), especially when handling the electrical parts, ECM etc..


When checking the ECM harness connector terminals from the connector wire side with the tester probe, be careful not to touch the other terminal by mistake. Do not insert the circuit tester test probes into the connector open side to test the continuity.

Before starting with a voltmeter connected to a suspected circuit, check to see if the battery is in fully charged condition.

Before disconnecting the ECM connectors, check that the ignition switch is "OFF" , and check and record codes stored in ECM memory. When disconnecting the ECM connectors, all three connectors should be removed (all stored codes will be cleared when this is done). When connecting a suspected circuit to the Battery + terminal or Engine ground, it will be advisable to install a test light (3.2W, 12V) in between, to protect electronic parts from being damaged.