Engine Electrical System

Diagnostic trouble code: P0645 “Malfunction in control circuit of A/C
compressor relay”
Item
No.
Operation procedure
Inspection
results
Follow-up
procedure
1
Connect the diagnostic tester and adaptor
and turn the ignition switch to “OFF”
position.
Proceed to next
step
Yes Proceed to step 4
2
Pull out the A/C compressor relay, turn the
ignition switch to “ON” position and check
if the voltage between the power supply
terminal of relay (i.e. 30# and 85# pins of
the relay) and the negative grid of power
supply is about 12V.
No
Proceed to next
step
Yes
Repair or replace
the wiring
harness.
3
Check if the power supply circuit of relay is
open or short to ground.
No Proceed to Step 2
Yes Replace the relay.
4
Inspect with multimeter to check if the
voltage between the control terminal of A/C
compressor relay (i.e. 86# pin of the relay)
and the negative grid of power supply is
about 3.7V.
No
Proceed to next
step
Yes
Repair or replace
the wiring
harness. 5
Check if the circuit between the control
terminal of A/C compressor relay (i.e. 86#
pin of the relay) and 70# pin of ECU is
open.
No
Refer to
diagnosis help.
E-58
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