Most 2000-2001 OBD2B Integra and 1999-2000 Civic engine harnesses do NOT have a tach signal wire from the distributor to the gauge cluster to operate the tachometer. This is because the OBD2B vehicle's gauge cluster gets the tach signal directly from the OBD2B ECU instead of the distributor. When installing an OBD2A ECU with an OBD2B to OBD2A jumper harness
or OBD1 ECU with an OBD2B to OBD1 jumper harness
into a 2000-2001 Integra or 99-00 Civic, the tachometer will no longer operate as the OBD2a and OBD1 ECU's do not output a tach signal to the gauge cluster tachometer.
To correct this, you will need to run a wire from the blue tachometer wire at the distributor to the gauge cluster tach wire (found on the driver's side shock tower connector) so that it "functions" like an OBD2A or OBD1 vehicle.Locate the blue wire from your distibutor. This wire will be found on the distributor connector side of the harness, but with no corresponding blue wire on the engine harness side.
On the driver's side shock tower, locate the grey harness connector. There will be a blue wire at this connector coming from the chassis harness, but no corresponding blue wire on the engine harness side of the connector.
Use a length of TXL or other automotive grade wire (preferably blue) and connect the blue wire at the distributor to the blue wire at the driver's side shock tower.
This will correct the "missing wire" from your engine harness and allow your tachometer to function correctly with your OBD2A or OBD1 ECU installed.