Volvo 850 Supplement Manual page 25

1) Ensure ignition is off. Connect test unit to ECC control
module. Check ground circuits. See DTC 1-2-1, OUTSIDE TEMP. SENSOR
CIRCUIT SHORTED TO GROUND. If ground circuits are okay, go to next
step.
2) Turn ignition on. Connect voltmeter between test unit pins
No. 6 and 27. Voltmeter should indicate 3 volts. If voltmeter
indicates one volt, there is no control signal to power stage. See DTC
4-1-8, NO CONTROL SIGNAL TO ECC POWER STAGE. If voltmeter indicates 4
volts, there is excessive voltage from power stage. See DTC 4-1-1,
PASSENGER COMPARTMENT FAN OVERCURRENT OR SEIZED FAN.
3) If voltmeter indicates 12 volts, check wire at ECC control
module terminal A27 (Violet/White wire) for a short to voltage. See
Fig. 10. If voltmeter indicates zero volts, wire has an open circuit
or is shorted to ground. Go to next step.
4) Ensure ignition is off. Disconnect power stage 4-pin
connector. See Figs. 14 and 15. Check Violet/White wire between power
stage connector terminal 2A and ECC control module terminal A27 for a
short to ground or open circuit. If wire is okay, go to next step.
5) Reconnect power stage 4-pin connector. Turn ignition on.
Connect voltmeter between test unit pins No. 6 and 5. If battery
voltage is present, go to next step. If zero volts are present, wire
is shorted to ground.
6) Ensure ignition is off. Disconnect power stage 4-pin
connector. Connect ohmmeter between test unit pin No. 5 and power
stage connector terminal 3A. If ohmmeter indicates continuity, replace
power stage. If ohmmeter indicates no continuity, check wiring for an
open circuit and repair as necessary.
DTC 4-2-0 ECC CONTROL MODULE FAULT, PROGRAM MEMORY
Erase DTC. Start and run engine. Turn engine off, leaving
ignition on. Check if DTC returns. If DTC returns, replace ECC control
module. Perform damper motor limit self-adjustment under TEST MODE 4.
DTC 5-1-1 SELF-ADJUSTMENT OF DAMPER MOTOR
LIMIT POSITIONS NOT CARRIED OUT
Erase DTC. ECC control module is programmed to carry out
self-adjustment of damper motor limit positions. Drive vehicle over 20
MPH for a few minutes. ECC control module will carry out self-
adjustment while driving. Stop vehicle and leave ignition on at least
2 minutes to enable ECC control module to store all values.
TESTING
WARNING: To avoid injury from accidental air bag deployment, read and
carefully follow all SERVICE PRECAUTIONS and DISABLING &
ACTIVATING AIR BAG SYSTEM procedures in the AIR BAG RESTRAINT
SYSTEM article in the ACCESSORIES/SAFETY EQUIPMENT section.
A/C SYSTEM PERFORMANCE
1) Ensure compressor drive belt is okay, fan motor runs at
all speeds, and that temperature vents shut completely with
temperature switch in full cooling position.
2) Ensure that all air comes from panel vents with mode
control on vent position, recirculation motor is working, and
condenser fan and cooling fan are working.
3) Start and warm engine to normal operating temperature.
Ensure compressor clutch engages when A/C is turned on. Set
temperature switch to full cold position, place mode control to vent
position, turn on recirculate air switch and blower fan switch high