C1389 ABNORMALITY OF TACHOMETER SIGNAL (ONLY VEHICLE WITH ES START)

1. Set the starter switch to "LOCK", disconnect the 28 pin connector of ABS+ES start ECU and the 12 pin connector of engine ECU.
2. Check the continuity between 7th terminal of the 28 pin connector of ABS+ES start ECU (chassis harness side) and 5th terminal of the connector of engine ECU (chassis harness side).
   Standard: No continuity
   
   
   　

Disconnection the wire harness.

[2] ENGINE ECU CHECK

1. Connect all the connector, turn the starter switch to "ON".
2. By using a oscilloscope, measure the voltage between 7th terminal of the 28 pin connector of ABS+ES start ECU and chassis ground.
   
   Check the waveform by stepping on the accelerator at "neutral position" of gear while engine is running.
   
   Standard: Under the pulse waveform of less than 25V to more than 6V, pulse interval will be shortened in proportion to engine revolution.

   

Abnormality of the engine ECU.

Abnormality of the ABS+ES start ECU.

1. Confirm the DTC C1389 is inactive

   • 　Start the engine and let it idling condition.
   • Verify the DTC C1389 is inactive.

   

   DTC Clear

   • Clear the DTC with Hino DX
   • Confirm the same DTC is not reoccurred

   

C1389 is reoccur: Return to first process Other DTC appear: Refer to concerned Trouble shooting

Complete