Tach Pulse Signal
- Timing control and triggering of fuel injectors are based upon input signals from TDC/CRANK/CYL sensors. These sensors are simple Permanent Magnet (PM) generator pick-up coils.
- Using a DVOM on low voltage scale (preferably with a bar-graph function), check for a pulsed low-voltage signal at proper ECU harness terminals with engine cranking. See Fig 1 . See WIRING HARNESS & SENSOR RESISTANCE TEST table. If a pulsed signal is present, no fault is present. If pulsed signal is not present, check sensor and wiring integrity.
- To test sensor and wiring integrity, turn ignition off. Disconnect connectors from ECU. Lightly probe appropriate ECU harness terminals to check for proper winding resistance of each sensor. See WIRING HARNESS & SENSOR RESISTANCE TEST table. If resistance is within specification, go to step 5). If resistance is not within specification, check resistance of TDC/CRANK/CYL sensor directly at sensor connector. See Fig 2 . See TDC/CRANK/CYL SENSOR RESISTANCE TEST table.
- If sensor resistance is now within specification, repair opens, shorts or corrosion in wire harness between sensor(s) and ECU. If resistance is not within specification, replace sensor.
- If resistance values in step 3) were within specification, check for continuity to ground at each ECU sensor terminal. If continuity is present, disconnect sensor(s) and recheck for continuity to ground at ECU harness sensor terminals. If continuity no longer exists, go to next step. If continuity to ground is still present, repair short to ground in ECU harness between ECU and sensor(s).
- If continuity did not exist with sensor disconnected, check for continuity to ground on each sensor connector terminal. See Fig 2
. See TDC/CRANK/CYL SENSOR RESISTANCE TEST
table. If continuity to ground exists, replace sensor.WIRING HARNESS & SENSOR RESISTANCE TEST
Application Terminals Ohms Accord CRANK B15 & B16 260-500 CYL B11 & B12 260-500 TDC B13 & B14 260-500 Civic & Prelude CRANK B15 & B16 350-700 CYL B11 & B12 350-700 TDC B13 & B14 350-700 TDC/CRANK/CYL SENSOR RESISTANCE TESTApplication Terminals Wire Color CRANK Sensor Wire 1 Of 2 "B" Blue/Green 2 Of 2 "F" Blue/Yellow CYL Sensor Wire 1 Of 2 "D" Orange 2 Of 2 "H" White TDC Sensor Wire 1 Of 2 "C" Orange/Blue 2 Of 2 "G" White/Blue