How do you clear the code on a Subaru Impreza?

All the below information is for the first generation Subaru Impreza, which is the pre-facelift model covering years from 1992 to 1997. All the details below would hep anyone Diagnose when their Check Engine light stays one and geared towards WRX, STI owners.

ECU Diagnostics

1. Vypněte zapalování
2. Connect read memory connectors [black connectors] (scroll down to «Finding Those Connectors» section to help you locate them)
3. Turn ignition ON (Engine OFF)
4. Engine Check lamp turns on
5. Code is indicated by Pulsing lamp
6. If Code is OK then Turn ignition OFF & Disconnect Connectors
7. Check ECU Code
8. Turn ignition OFF & Disconnect Connectors
9. If there is a fault Check Appropriate Sensor

Resetování ECU

An ECU reset will restore the car to factory default settings. This will remove any stored fault codes and restore ignition advance. Note that on the early Subaru models (especially pre 1997) the ECU purposely retards the ignition when any knock is detected, however, and it takes its time to advance the timing again.

It is possible to reset the ECU by following steps:

1. Vypněte zapalování
2. Connect Read Memory Connectors [black connectors] & Test Mode Connectors [green connectors] (scroll down to «Finding Those Connectors» section to help you locate them)
3. Turn ignition ON (engine off)
4. Engine Check lamp turns on
5. Depress accelerator pedal completely
6. Then return it to the half-throttle position and hold it there for two seconds
7. Release pedal completely
8. Nastartujte motor
9. Code is indicated by Pulsing lamp
10. If a fault is detected — Check ECU Code
11. If no fault is detected — drive the car sensible for a couple of minutes until warm (don’t push it and take it easy like a grandpa!)
12. When the ECU has been reset the Check Engine Light will flash
13. Code is indicated by Pulsing lamp
14. If a fault is detected Check ECU Code
15. Turn ignition OFF & Disconnect Connectors
16. If there is a fault Check Appropriate Sensor

Finding Those Connectors

As indicated above, the Black Read Memory Connectors & the Green Test mode Connectors are required to perform diagnostic & ECU resets. The connectors are located under the dash up by the steering column. If they have not been used before they are usually taped quite high up & can be difficult to find, but they are there, once untaped they dangle down and are quite easy to use.

Reading ECU Codes

The ECU codes are displayed as pulses of the Check Engine Light.

Normální použití

• CEL On — If Check Engine Light stays on there is a fault.
• CEL Off — If Check Engine Light goes out there is no fault.

Diagnostický režim

Flashing: Even and Continuous

No Fault is indicated by the Check Engine Light continuously & evenly flashing on/off (this is also used to indicate the successful completion of an ECU Reset).

Flashing: Abruptly with a pattern

The long pulses (1.3 Seconds) indicate Tens and the short pulses (0.2 Seconds) indicate ones. Pulses are separated by Short Pauses (0.2 Seconds), multiple codes are separated by a Long Pause (1.8 Seconds).

The simplest way for an inexperienced mechanic to retrieve codes is to write the codes down in a sort of Morse Code (dots and dashes), and start a new line when you get a 1.8 Second pause (for NEW code), and then add the actual numbers up after code retrieval is completed.

Subaru ECU Codes

All codes below are the generic Subaru ECU error codes, the highlighted ones are specific codes for the Impreza.

Senzory

Please refer to the photo and the reference guide for the location of each sensor in the engine bay of your Subaru Impreza. If you are currently debugging a problem from the fault given by the ECU code mentioned above then one of the following applies:

• Sensor is disconnected, or wire is cut somewhere in the harness. Using a voltmeter to check continuity can help cross out this possible issue.
• Faulty Sensor. Either research the possible values the sensor should own to (usually in ohms), or if possible replace the sensor with a known working one.
• Faulty Mechanics. It could be the real fact that the mechanics the sensor is built to detect a fault on is actually not performing as it should.