Retrieving diagnostic trouble codes from your 1990 Toyota Corolla doesn’t require a scan tool. This model utilizes an OBD I system, which allows for manual code retrieval. This guide provides a step-by-step process to access and interpret these codes, helping you understand what might be triggering your check engine light.
Understanding the beauty of the OBD I system in your 1990 Corolla lies in its simplicity. You can perform a manual scan, eliminating the immediate need for specialized diagnostic equipment. By using a simple jumper wire, you can access the stored trouble codes and begin diagnosing your vehicle’s issue.
Checking the trouble codes that are activating your check engine light (Malfunction Indicator Light – MIL) on your OBD I Toyota Corolla involves bridging the TE1 and E1 terminals within the Data Link Connector (DLC). This is done using a jumper wire with the ignition key turned to the ‘On’ position, but without starting the engine (Key On Engine Off).
Once the jumper wire is correctly placed, the malfunction indicator light (MIL) will begin to flash, communicating the trouble codes stored within the fuel injection computer’s memory.
Reading the Flashing Check Engine Light for OBD I Codes
As previously mentioned, your OBD I Toyota Corolla will communicate diagnostic codes through flashes of the malfunction indicator light (MIL), also known as the check engine light (CEL), after you’ve connected terminals TE1 and E1 in the diagnostic link connector (DLC).
The DLC is located in the engine compartment, specifically on the left strut tower.
Here are the steps to manually retrieve the trouble codes:
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Battery Check: Ensure your car battery is fully charged before starting the process. It’s advisable to connect a battery charger during code retrieval to prevent battery drain.
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Ignition ON: Turn the ignition key to the ‘On’ position. Do not start the engine.
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Jumper Wire Connection: Locate the diagnostic link connector (DLC) in the engine compartment and use a jumper wire to connect terminals TE1 and E1.
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Count the MIL Flashes: Observe and count the flashes of the malfunction indicator light (MIL).
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No Trouble Codes Present: If no trouble codes are stored, the MIL will flash continuously and evenly.
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Trouble Codes Present: If there are trouble codes, the MIL will flash in a specific pattern to represent these codes.
- Digit Flashes: The digits of each trouble code are indicated by flashes approximately 0.5 seconds long.
- Inter-Digit Pause: A 1.5-second pause separates the first and second digits of a code.
- Inter-Code Pause: If multiple trouble codes are stored, a 2.5-second pause will separate each subsequent code.
- Code Repetition Pause: After all codes have been flashed, there will be a 4.5-second pause before the sequence repeats.
- Code Order: Trouble codes are flashed in ascending numerical order, from the smallest to the largest.
Once you have accurately recorded the trouble codes, disconnect the jumper wire from the diagnostic link connector (DLC) and turn the ignition key to the ‘Off’ position.
Diagnostic Link Connector (DLC) Location on a 1990 Corolla
The diagnostic link connector (DLC) on your 1990 Toyota Corolla is positioned within the engine compartment for easy access during diagnostics. Specifically, you will find it attached to the left-side strut tower. This location is designed to be readily accessible for technicians and DIYers alike.
Toyota OBD I Diagnostic Trouble Code Definitions (1990-1995 Corolla)
The following table lists the OBD I trouble code definitions for 1990-1995 EFI Toyota Corolla models. Understanding these codes is crucial for diagnosing the problem indicated by your check engine light.
| 1990-1995 EFI Toyota Corolla OBD I Trouble Code Definitions |
|---|
| Code |
| 11 |
| 12 |
| 13 |
| 14 |
| 21 |
| 22 |
| 24 |
| 25 |
| 26 |
| 27 |
| 31 |
| 31 |
| 41 |
| 42 |
| 43 |
| 51 |
| 52 |
| 53 |
| 71 |
| 72 |
By following these steps and utilizing the provided code definitions, you can effectively diagnose issues with your 1990 Toyota Corolla using its built-in OBD I diagnostic system. This method provides a straightforward way to understand your vehicle’s health without needing a modern OBD2 scanner.
