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Toyota Code Retrieval

Accessing Diagnostic Trouble Codes

1982-87

The ECU self diagnosis circuit detects and stores system malfunctions related to the various sensor and actuator circuits. These malfunctions are stored as DTC's 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 DTC's, system malfunctions can be easily diagnosed and repaired. To obtain DTC's 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 diagnostic trouble code after engine starts, check diagnosis circuit.
  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. Turn ignition switch on but do not start engine.

1984 5M.GE Engine

  1. Short terminals of check engine connector, using a jumper wire, and connect a suitable analog voltmeter to EFI connector, using harness 09842-14010. Use a analog voltmeter with a high (10K ohm) impedance.
  2. Diagnostic trouble codes will be indicated by voltmeter deflection in the 0-25 volt and 2.5-5.0 volt ranges.

Except Cressida & Supra Equipped w/Super Monitor Display

  1. Short terminals of check engine connector or service connector (depending on model) with suitable jumper wire.
  2. Diagnostic trouble codes will be indicated by the number of flashes of the "Check Engine" lamp.

Cressida & Supra Equipped w/Super Monitor Display

  1. With ignition On and engine not running, simultaneously depress and hold Select and Input M keys of Super Monitor display for at least three seconds.
  2. The letters DIAG will appear on the display. After a short pause, depress and hold Set key for at least three seconds. If there are no DTC's stored in the ECU, the display will read E/G OK or ENG-OK (depending on models). If there are DTC's stored in the ECU, the DTC number will appear on the display. If there is more than one DTC, there will be a three second pause between DTC's.
  3. After accessing diagnostic trouble codes, clear display by turning Off ignition switch or depress the Super Monitor Display key so the time appears.

1988-95 Normal Mode

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 ECM (ECU) self diagnosis circuit detects and stores system malfunctions related to the various sensor and actuator circuits. These malfunctions are stored as DTC's in the ECM (ECU) memory as long as battery voltage is applied to the ECM (ECU), and in most cases, the Check Engine lamp will flash as long as a malfunction is present. By analyzing these DTC's, system malfunctions can be easily diagnosed and repaired. To obtain DTC's stored in the ECM (ECU) memory, proceed as follows:

  1. Short terminals of check engine connector or service connector (depending on model) with suitable jumper wire.
  2. Diagnostic trouble codes will be indicated by the number of flashes of the Check Engine lamp.

Two Trip Detection Logic

When a logic malfunction is first detected, the malfunction is temporarily stored in the ECM (ECU) memory. If the same case is detected again during the second drive test, the second detection causes the Check Engine light to illuminate. In order for this mode to store DTC's, the ignition switch must be turned Off between the first and the second test. Refer to "Diagnostic Trouble Code Interpretation" in each specific section for applicable two trip detection logic DTC's.

Test Mode

The test mode has a higher sensing ability to detect faults than in normal mode. It can detect malfunctions in the starter signal circuit, air conditioning signal and neutral start switch signal. In addition, the test mode also detects the same malfunctions as in the normal mode.

  1. Ensure battery voltage is at least 11 volts, throttle valve is fully closed, transmission is in neutral position and accessories in Off position.
  2. Short check service connector terminals TE2 and El, with suitable jumper wire, then turn ignition switch On to enter test mode, check engine lamp should illuminate. Test mode may not be entered if terminals TE2 and El are shorted after ignition switch is turned On.
  3. Start engine and drive vehicle at 10 mph or higher. If vehicle is not driven vehicle speed signal DTC's 42 and 43 may be stored.
  4. Simulate malfunction conditions.
  5. Using suitable jumper wire, short check connector terminals TE1 and El, then read DTC's.

Toyota Hand-Held Tester

Diagnostic trouble codes may be retrieved by connecting the Toyota hand-held tester to the diagnostic link connector (DLC), then following the prompts on the tester screen.


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