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PostSubject: ECU Error Code Procedure    ECU Error Code Procedure  I_icon_minitime2010-11-29, 6:43 pm

Before testing ECI components, perform diagnosis and basic engine checks (ignition system malfunctions, incorrect engine adjustments, etc.) Perform ECI diagnosis only after conventional components inspected.


The diagnostic system, which monitors all input signals from each sensor, is an integral part of the ECU. If an abnormal input signal occurs, that item is memorized by the ECU. There are 6 diagnostic codes which can be confirmed using a multimeter.

If two or more systems are non-functional, they are indicated in order of increasing code number. Indication is made by deflection of the multimeter pointer. A constant 12 volts indicates system is normal. If system is abnormal, voltmeter will alternate between 0-12 volts every .4 seconds to display codes. After indication of zero volts for 2 seconds, the higher code is indicated.

NOTE: ECU abnormal diagnostic memory is kept by direct power from the battery. Memory is not erased by turning the ignition off, but will be erased if the battery or ECU is disconnected.

Diagnostic Codes Table

Diagnostic Code................Diagnostic
1......................Oxygen Sensor & Computer
2 .....................Engine Speed Sensor
3......................Airflow Sensor
5......................Throttle Position Sensor
6......................ISC Motor Position Sensor
7......................Coolant Temperature Sensor
.....(code 4 is for Cordia/Tredia only.)


1.) Turn ignition switch to "OFF" position. Connect voltmeter to self--diagnostic output harness connector located in glove box.

(This coonnector is located top center of the glove box!)

2) Turn ignition switch to "ON" position and ECU will display code(s). Record any abnormal diagnostic codes and perform necessary component repairs. After checking and repair, turn Ignition off and disconnect negative battery cable for 15 seconds or more to erase ECU memory.

NOTE: Oxygen sensor memory is erased when ignition is turned off.
To diagnose oxygen sensor, drive vehicle a good distance and keep engine running.

Diagnostic Code 1 (Oxygen Sensor) If oxygen sensor signal does not change for 20 seconds or more in feedback range, check wiring harness and connector, oxygen sensor and ECU.

Diagnostic Code 2
(Engine Speed Sensor) While cranking engine, if input of ignition signal is not applied to computer for 3 seconds or more, check wiring harness and connector, ignitor and ECU.

Diagnostic Code 3 (Airflow Sensor) On all models, if airflow sensor maximum output is 10 cycles per second while engine is idling, check wiring harness and connector, airflow sensor and ECU. On Cordia and Tredia models. if engine stalls and output rises to 100 cycles per second, check wiring harness and connector, airflow sensor and ECU.

Diagnostic Code 4 (Pressure Sensor) If pressure sensor output is 4 5 volts or more, or .2 volt or less, check wiring harness and connector, pressure sensor and ECU.

Diagnostic Code 5 (Throttle Position Sensor) If throttle position sensor output is 2 volt or less, or is 4 volts or higher for one second or more while engine is idling (idle switch on), check wiring harness and connector, TPS and ECU.

Diagnostic Code 6 (ISC Motor Position Sensor) On Cordia and Tredia models, if throttle position sensor output is .4 volt with L switch off, check wiring harness and connector, ISC servo and ECU. On all others, if motor position sensor output is 4.8 volts or more, or .2 volt or less, check wiring harness and connector, MPS and ECU.

Diagnostic Code 7 (Coolant Temperature Sensor) If coolant temperature sensor output is .1 volt or less, or 4.5 volts or more, check wiring harness and connector, coolant temperature sensor and ECU.
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