Volvo 850 Supplement Manual page 17

1) Run engine and check whether temperature gauge in
instrument cluster works. If temperature gauge works, engine
temperature signal is reaching instrument panel, but Green/Gray wire
between ECC control module terminal A23 and instrument cluster has an
open circuit. See Fig. 10.
2) If temperature gauge does not work, temperature sensor
wiring may be shorted or engine temperature signal may be absent from
engine management system.
3) To check wiring, turn ignition off. Check Green/Gray wire
between ECC control module terminal A23 and instrument cluster for a
short to ground or voltage. If no fault is found, problem may be in
engine management system. See the G - TESTS W/CODES article in the
ENGINE PERFORMANCE section.
DTC 1-4-1 & 1-4-3 DRIVER'S OR PASSENGER'S SIDE TEMP.
SWITCH FAULTY CONTROL SIGNAL
These codes may be caused by an internal fault in ECC control
module, temperature switch, or internal wiring. Erase DTCs. Turn
ignition off, then on. Test ECC system. See TEST MODE 1 through 4
under TROUBLE SHOOTING. Check if DTCs return. If DTCs return, replace
ECC control module. Perform self-adjustment of damper motor limit
positions under TEST MODE 4.
DTC 1-4-5 AIR DISTRIBUTION SWITCH FAULTY CONTROL SIGNAL
Code may be caused by an internal fault in ECC control
module, air distribution switch, or internal wiring. Erase DTCs. Turn
ignition off, then on. Test ECC system. See TEST MODE 1 through 4
under TROUBLE SHOOTING. Check if DTCs return. If DTCs return, replace
ECC control module. Perform self-adjustment of damper motor limit
positions under TEST MODE 4.
DTC 1-5-1 & 1-5-2 FAN SPEED SENSOR CONTROL SIGNAL MISSING,
SIGNAL TOO HIGH OR SIGNAL SHORTED TO GROUND
Codes may be caused by an internal fault in ECC control
module, fan speed switch, or internal wiring. Erase DTCs. Turn
ignition off, then on. Test ECC system. See TEST MODE 1 through 4
under TROUBLE SHOOTING. Check if DTCs return. If DTCs return, replace
ECC control module. Perform self-adjustment of damper motor limit
positions under TEST MODE 4.
DTC 2-1-1, 2-2-1, 2-3-1, 2-3-3 & 2-3-5 DRIVER'S OR
PASSENGER'S SIDE DAMPER MOTOR POSITION SENSOR CIRCUIT
OPEN OR SHORTED TO POWER
1) Check if DTCs 1-2-2, 1-2-4, 1-2-6, 2-1-1, 2-2-1, 2-3-1, 2-
3-3 and2-3-5 are present. If all DTCs are not present, there is an
open or short circuit in a wire between ECC control unit and damper
motor which applies to DTC. See AUTOMATIC A/C-HEATER SYSTEM DIAGNOSTIC
TROUBLE CODES table, then go to next step. If all DTCs are present, an
open circuit is present in common ground at ECC terminals A9 and A10.
See Fig. 10.
2) Ensure ignition is off. Connect test unit between ECC
control unit and control unit connector. Check ECC grounds. See DTC 1-
2-1, OUTSIDE TEMP. SENSOR CIRCUIT SHORTED TO GROUND. Also check power
supply to damper motor position sensor. See TEST MODE 2 under TROUBLE
SHOOTING. If ECC grounds and power supply to damper motor position
sensor are okay, go to next step.
3) Turn ignition on. Connect voltmeter between test unit pins
No. 10 and No. 17 (driver's side damper motor), No. 18 (passenger's