DTC P0480 Cooling Fan Relay No. 1 Low Input
- Turn ignition off. Connect test mode connector (under left side of dash). Turn ignition on. Using a voltmeter connected to ground, backprobe PCM connector terminal No. 74 (Red/Blue wire). If voltage does not change between 0 and 10 volts, go to next step. If voltage changes between 0 and 10 volts, check for poor contact at PCM connector.
- Turn ignition off. Disconnect PCM connectors. Using an ohmmeter connected to ground, measure resistance at PCM connector terminal No. 74. If resistance is more than 10 ohms, go to next step. If resistance is 10 ohms or less, check for short to ground in radiator fan relay No. 1 control circuit. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
- Remove main relay from A/C relay holder. Turn ignition on. Measure voltage between ground and main fan relay connector terminal No. 28. See Fig 1. If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, check for an open in harness between ignition switch and A/C relay holder connector. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
- Turn ignition off. Measure resistance between main fan relay terminals No. 27 and 28. See Fig 2. If resistance is not between 74 and 118 ohms, replace main fan relay. If resistance is as specified, measure resistance of harness between PCM connector terminal No. 74 and main fan relay connector terminal No. 27. If resistance is one ohm or less, go to next step. If resistance is more than one ohm, check for an open in harness between PCM and A/C relay connector.
- Check for poor contact at PCM or main fan relay connector. If connections are okay, replace PCM.