Tach Pulse Signals

Timing control and triggering of the fuel injectors are based upon input signals from the TDC, CRANK, and CYL sensors. These sensors are simple PM (Permanent Magnet) generator pick-up coils.

1. Test for a pulsed voltage signal being generated by each sensor. Using a DVOM on the low-volts scale (preferably with a bar-graph function), check for a pulsed voltage signal at the proper ECU harness terminals with engine cranking. See ECU TACH SIGNAL & RESISTANCE TEST TERMINALS  . If pulsed signal is not present, check sensor and wiring integrity.
2. To test sensor and wiring integrity, turn ignition off. Lightly probe appropriate ECU harness terminals to check for proper sensor winding resistance of each sensor. If resistance is not within specification, go to step 4).
   ECU TACH SIGNAL & RESISTANCE TEST TERMINALS
   
   

   Application	Terminals	Resistance (Ohms)
   CRANK	B10 & B12	350-550
   CYL	C1 & C2	700-1000
   TDC	C3 & C4	350-550

3. If resistance is within specification, check for continuity to ground on each terminal. If continuity exists, disconnect appropriate sensor connector and recheck for continuity to ground at ECU terminal. If continuity still exists, repair short to ground in harness. If not, replace appropriate sensor.
4. Disconnect sensor connector at sensor. See Fig 1 and Fig 2 . Check for appropriate sensor resistance value. See SENSOR TEST TERMINALS IDENTIFICATION  . If sensor resistance is within specification, repair open, short or corrosion in sensor harness between ECU and sensor. If sensor resistance is not within specification, replace sensor.
   SENSOR TEST TERMINALS IDENTIFICATION
   
   

   Application	Terminal or Wire Color
   CYL	White & Orange
   CRANK	D & E
   TDC	B & C

   Fig 1: Integra CYL Sensor Connector Identification

   Courtesy of AMERICAN HONDA MOTOR CO., INC.
   Fig 2: Integra TDC/Crank Sensor Connector Identification

   Courtesy of AMERICAN HONDA MOTOR CO., INC.