LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Acura >> 1990 >> Legend Base, 4D Sedan, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> Ignition Checks >> Electronic Ignition System >> Tach Pulse Signals
September 30: LEMON manuals is back up on a temporary server! Slowness is possible

Tach Pulse Signals

  1. Timing control and triggering of the fuel injectors are based upon input signals from the TDC/CRANK/CYL sensors. These sensors are simple PM (Permanent Magnet) generator pick-up coils.
  2. Test for a pulse voltage signal being generated by each sensor. Using a DVOM on the low-volts scale (preferably with a bar-graph function), check for a pulse voltage signal at the proper ECU harness terminals with engine cranking. See ECU TACH SIGNAL & RESISTANCE TEST TERMINALS  table. If pulse signal is not present, check sensor and wiring connections.
  3. To test sensor and wiring connections, 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 5).
    ECU TACH SIGNAL & RESISTANCE TEST TERMINALS

    Application ECU Terminals (1) Resistance (Ohms)
    Integra
    CRANK B10 & B12 350-700
    CYL C1 & C2 350-700
    TDC C3 & C4 350-700
    Legend
    CRANK B19 & B20 500-1000
    CYL C1 & C2 500-1000
    TDC C3 & C4 500-1000
    (1) Terminal identifications are imprinted on ECU connector.
  4. If resistance is within specification, check for continuity to ground on each terminal. If continuity exists, disconnect appropriate sensor connector and recheck appropriate ECU terminal for continuity to ground. If continuity still exists, repair short to ground in harness. If not, replace appropriate sensor.
  5. Disconnect sensor connector at sensor. See Fig 1 and Fig 2 . Check for appropriate sensor resistance value. See ECU & SENSOR TEST TERMINAL IDENTIFICATIONS  and ECU TACH SIGNAL & RESISTANCE TEST TERMINALS  tables. 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.
    ECU & SENSOR TEST TERMINAL IDENTIFICATIONS

    Application (1) ECU Terminals (2) Sensor Terminals
    Integra
    CYL C1 & C2 F & G
    CRANK B10 & B12 C & D
    TDC C3 & C4 A & B
    Legend
    CYL C1 & C2 White & Orange
    CRANK B19 & B20 Blue/Yellow & Blue/Green
    TDC C3 & C4 White/Blue & Orange/Blue
    (1) Terminal IDs are imprinted on ECU connector.
    (2) On Legend, terminals' wire color are given.
    Fig 1: Identifying Integra Sensor Connector Terminals
    G90C15026Courtesy of AMERICAN HONDA MOTOR CO., INC.
    Fig 2: Identifying Legend CYL/Crank Sensor Connector Terminals
    G120086Courtesy of AMERICAN HONDA MOTOR CO., INC.
    Fig 3: Identifying Legend TDC Sensor Connector Terminals
    G120087Courtesy of AMERICAN HONDA MOTOR CO., INC.
scientia non olet · About LEMON Manuals