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ECU Trouble Codes

By Danny Pham

How to Read the Trouble Codes from the ECU

  1. Locate the ECU (under your dash in the center) and look for a small screw next to a LED (towards the back end).
  2. Turn the ignition to the ON position (engine not running).
  3. Turn the screw fully clockwise, wait 2 seconds, and then turn it fully counter-clockwise.

The LED will start to display the code by a series of long flashes, followed by a series of short flashes. Your check engine light on the instrument cluster will also flash in the same sequence. This sequence will repeat.

Trouble Codes

Click here to see the trouble codes for the 200SX SE-R

The following is from the Haynes manual for 91-94 Sentras (both 1.6 and 2.0).

Flashes (long, short) Circuit or system
1,1 Crank angle sensor/circuit
1,2 Mass airflow sensor/circuit
1,3 Coolant temp sensor
1,4 Vehicle speed sensor
2,1 Ignition signal
3,1 ECM control unit
3,2 EGR function
3,3 Oxygen sensor
3,4 Knock sensor
3,5 Exhaust gas temp sensor
4,3 TPS - Throttle position sensor
4,5 Injector leak

Resetting the ECU

Once the screw is turned fully clockwise and counter-clockwise again, the ECU will be reset.