Tech:Engine/A Series/Diagnostic System

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This is the early 4age ECCS diagnostic codes or what is referred to as the 'single digit' taken from they toyota diagnostic manual.

01 - Normal Condition. "Check Engine" light off.

02 - Intake Vacuum Signal. Intake manifold pressure signal is open or short circuit. "Check Engine" light on.

03 - Ignition Signal. Ignition conformation signal (IGf) was not received four times in a row. "Check Engine" light on.

04 - Water Temp. Sensor Signal. Water thermosignal is open or short-circuited. "Check Engine" light on.

06 - RPM Signal. G or Ne signal was not received when the engine was cranked for two seconds or longer. Ne signal was not received for 50 msec at engine speed over 1,000rpm. "Check Engine" light on.

07 - Throttle Position Sensor Signal. Throttle opening angle signal is open or short-circuited. "Check Engine" light off.

08 - Intake Air Temp. Signal. Intake air thermo signal is open or short-circuited. "Check Engine" light off.

09 - Vehicle Speed Sensor Signal. Signal from the vehicle speed sensor is 0km/h for several seconds when the engine speed is faster then 2,800rpm and the intake manifold pressure signal is over rated value. "Check Engine" light off.

10 - Starter Signal. STA signal was not received until the engine exceeded 800rpm at vehicle speed 0km/h. "Check Engine" light off.

11 - Switch Signal. Air conditioning switch IDL point in the throttle position sensor is ON. (NOT REGISTERED IN MEMORY.) "Check Engine" light off.


1. Including "Normal", the ECU is programmed with the 10 diagnostic codes shown above. 2. When 2 or more codes are indicated, the lowest number (code) will appear first. 3. All detected diagnostic codes, except 11, will be retained in memory by the ECU from the time of detection until cancelled out. 4. Once the malfunction is cleared, the "CHECK ENGINE" warning light on the instrument panel will go out but the diagnostic code(s) will remain stored in the ECU memory (except for code no. 11). 5. For the code numbers that have "OFF" in the "CHECK ENGINE" Diagnostic Light column, the CHECK ENGINE light does not go on if the indicated malfunction occurs. However, the trouble codes (except for code no. 11) are still stored in the memory of the ECU.

My personal addition:

There is also code 5 - o2 sensor, which was only published with the later diagnostic codes that will present itself.

To clear the codes you can do one of two things:

1. Pull the "STOP" light fuse out of the drivers side kick panel to reset the fault codes, refit the fuse and check for codes, take it for a drive and recheck.

2. Take the negative battery cable off of the battery (make sure nothing is still touching the negative pole of the battery) and touch it onto the positive battery cable (still connected to the battery) for 5 seconds then reattach it to the negative terminal. Recheck for codes.