Volvo 850 Supplement Manual page 16

4) If voltmeter indicates 5 volts, check duct temperature
sensor wiring for an open circuit. Go to next step. If voltmeter
indicates 12 volts, check wiring for short to voltage between
connector terminal No. 2 (Green or Yellow wire) and ECC control module
terminal C1 (driver's side) or C2 (passenger's side). See Figs. 8 and
10.
5) Ensure ignition is off. Disconnect ECC control module, but
leave test unit connected to control module connector. Disconnect
connector from each duct temperature sensor. Connect jumper wire
between duct temperature sensor connector terminals.
6) Check driver's side duct temperature sensor wiring by
measuring resistance between test unit pins No. 56 and 47. Check
passenger's side duct temperature sensor wiring by measuring
resistance between test unit pins No. 56 and 48.
7) If continuity is present, wiring is okay but duct
temperature sensor has an open circuit. Replace duct temperature
sensor. If continuity is not present, duct temperature sensor is okay
but an open circuit is present in wiring. Repair wiring for an open
circuit.
Fig. 10: Identifying ECC Control Module Terminals
Courtesy of Volvo Cars of North America.
DTC 1-3-5 NO ENGINE TEMPERATURE FREQUENCY SIGNAL