Reading Diagnostic Trouble Codes

Self diagnosis circuit check:

Prior to considering the TCCS system as cause for a complaint, ensure the battery is fully charged and the engine and all related systems are operating properly. When diagnosing TCCS malfunctions, observe all precautions and follow procedures as outlined to ensure successful repairs.
The ECU self diagnosis circuit detects and stores system malfunctions related to the various sensor and actuator circuits. These malfunctions are stored as codes in the ECU memory as long as battery voltage is applied to the ECU, and in most cases, the ``Check Engine'' lamp will flash as long as a malfunction is present. By analyzing these codes, system malfunctions can be easily diagnosed and repaired. To obtain codes stored in the ECU memory, proceed as follows:
1. Turn ignition switch to On position and observe ``Check Engine'' lamp, then start engine and observe lamp.
2. If lamp fails to light with ignition switch On (engine stopped), or if lamp fails to go out or flash a trouble code after engine starts, check diagnosis circuit, Fig. 11.
3. Run engine until it reaches normal operating temperature, then stop engine.
4. Ensure that battery voltage is at least 11 volts, throttle valve is fully closed, A/C is off and that transmission selector is in park or neutral.
5. Turn ignition switch on but do not start engine.

Fig. 7 TCC Check Connector:

Fig. 8 EFI Connector Test Connections:

6. Short terminals of check engine connector, Fig. 7, using a jumper wire and connect a suitable analog voltmeter to EFI connector, Fig. 8, using harness 09842-14010.
NOTE: Use an analog voltmeter with a high (10K ohm) impedance.
7. Diagnostic codes will be indicated by voltmeter deflection in the 0-2.5 volt and 2.5-5.0 volt ranges.