Tach Pulse Signals
- 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.
- 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.
- 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. - 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.
- 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. Courtesy of AMERICAN HONDA MOTOR CO., INC.