The PGM-FI Main Relay is actually comprised of two individual internal relays. When the ignition switch is initially turned ON , the Powertrain Control Module (PCM) supplies ground to the PGM-FI Main Relay. This ground triggers one of the PGM-FI internal relays that sends battery voltage to the fuel pump for two seconds to pressurize the fuel system.
When the engine is running the PCM supplies a continuous ground to the PGM-FI Main Relay. The supplied ground keeps the relay in the "closed" position providing electrical current to the fuel pump, keeping the fuel loop pressurized while the engine runs.
If the engine is not running with the ignition on, the PCM cuts the ground to the PGM-FI Main Relay, causing the relay to "open" and stop the electric current flow to the fuel pump. As mentioned previously, if the engine is not running, the PCM will only supply ground to the PGM-FI Main Relay for two seconds when the ignition switch is initially switched to the ON position.
The PGM-FI Main Relay also supplies electrical power to the Idle Air Control (IAC) Valve and to the fuel injectors.
If the engine starts and continues to run, the PGM-FI Main Relay is working and does not need to be replaced.
- Locate and remove the relay.
On some models of the Civic and Civic del Sol it is located to the left of the steering column under the dash. Many later models position it either near the passenger right side kick panel under the dash or by the driver left side kick panel up under the dash.
- Attach the battery positive terminal to the No. 2 terminal.
- And the battery negative terminal to the No. 1 terminal.
- Check for continuity between terminal No. 5 and 4.
- If there is no continuity, replace the relay and retest.