C70, S70 & V70 (Fuel Gauge Does Not Operate)

Turn ignition off. Remove right side panel in trunk. Disconnect Black 2-pin electrical connector. See Fig 1. Connect an ohmmeter between sensor connections. Depending on amount of fuel in tank, if ohmmeter indicates 8 ohms (full) to 330 ohms (empty), go to next step and check sensor ground connection. If ohmmeter does not indicate 8-330 ohms, replace fuel level sensor. See FUEL LEVEL SENSOR under REMOVAL & INSTALLATION.
Ensure ignition is off. Connect an ohmmeter between harness connector terminal No. 2 (Yellow/Red wire) and ground. If about zero ohms is present, go to next step and check sensor signal circuit. If about zero ohms is not present, check for an open circuit in wiring between connector terminal No. 2 (Yellow/Red wire) and 30-pin connector on instrument cluster.
Connect voltmeter between harness connector terminal No. 2 (Yellow/Gray wire) and ground. Turn ignition on. If about 7 volts are present, replace instrument cluster. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION. If zero volt is present, check for a short to ground or an open circuit. If battery voltage is present, check wiring for a short to voltage.

Fig 1: Locating Black 2-Pin Connector In Trunk

Courtesy of VOLVO CARS OF NORTH AMERICA.