How to Check for ECU trouble codes on a SW20

Checking the Engine ECU codes on a Toyota MR2 (SW20) is a straightforward process. Here’s a step-by-step guide:

Tools Needed:

• A paperclip or jumper wire
• Notepad and pen (to write down the codes)

Step 1: Locate the Diagnostic Port

• Open the engine bay and locate the Diagnostics Box.
• It is a small, black or gray plastic box labeled “DIAGNOSIS” near the firewall

Step 2: Open the Diagnostics Box

• Flip open the plastic cover of the diagnostics box.
• Inside, you’ll see multiple terminals labeled with letters.

Step 3: Jumper the Correct Terminals

• Use a paperclip or jumper wire to connect (bridge) the TE1 and E1 terminals.
  • TE1 = Test Engine
  • E1 = Ground

Step 4: Turn the Ignition to “ON” (Without Starting the Engine)

• Insert the key and turn it to the “ON” position.
• Do NOT start the engine.

Step 5: Observe the Check Engine Light (CEL) Flashes

• The Check Engine Light (CEL) on the dashboard will begin to flash in a pattern.
• Each code consists of two-digit numbers.
  • Example: Code 21 will flash as two slow blinks, then one fast blink.

Step 6: Interpret the Codes

• If there are multiple codes, they will be separated by a short pause.
• If only one code repeats, that is the only stored error.
• A continuous, steady blinking (no pause) means no stored codes—the system is normal.

Step 7: Look Up the Code Meaning

Listed below are the most common ecu codes

Step 8: Reset the ECU (Optional - To Clear Codes)

• Disconnect the negative (-) battery terminal for 3 minutes or remove EFI fuse in engine bay to depower the computer
• Reconnect the battery / or reinstall fuse and start the car.
• Check if the issue persists.

Toyota MR2 (SW20) OBD-I Trouble Codes

These codes are retrieved by counting the flashes of the Check Engine Light (CEL) after bridging TE1 and E1 in the diagnostic port.

Code       Problem                                                                       Possible Causes

Toyota MR2 (AW11) OBD-I Trouble Codes

With the car off, connect E1 and T1 together with a bare paper clip. Turn the key on but don't start the car. The CEL will flash and give you codes. Non-stop rapid flashing means no codes are stored.

Each code is displayed as a sequence of blinks on the Check Engine Light (CEL).

Code      Problem                                                                  Possible Causes

How to Clear ECU Codes (Reset the ECU)

1. Disconnect the negative (-) battery terminal for 10-15 minutes.
2. Reconnect the battery and turn the ignition to ON (without starting).
3. Recheck for codes—if the same code returns, the issue needs further troubleshooting.

This list covers all known OBD-I codes for the Toyota MR2 (AW11). Let me know if you need help troubleshooting a specific code! 🚗💨