Honda Civic. Manual — part 763

YES - Check for loose wires or poor connections at the HVAC control unit
24P connector. If the connections are good, substitute a known-good HVAC
control unit, and recheck.

NO - Check for an open in the wire between the HVAC control unit and body
ground. If the wire is OK, check for poor ground at G504 (see CONNECTOR
TO HARNESS INDEX ).

RADIATOR AND A/C CONDENSER FAN LOW SPEED CIRCUIT
TROUBLESHOOTING

1. Check the No. 7 (20 A: M/T) or (30 A: A/T) fuse in the under-hood fuse/relay

box, and the No. 36 (10 A) fuse in the under-dash fuse/relay box.

Are the fuses OK?

YES - Go to step 2.

NO - Replace the fuses, and recheck. If the fuses blow again, check for a short
in the No. 7 (20 A: M/T) or (30 A: A/T) and No. 36 (10 A) fuses circuit.

2. Remove the radiator fan relay from the under-hood fuse/relay box, and test it

(see REMOVAL AND INSTALLATION ).

Is the relay OK?

YES - Go to step 3.

NO - Replace the radiator fan relay.

NOTE:

Do not use this troubleshooting procedure if the A/C
compressor is inoperative. Refer to the SYMPTOM
TROUBLESHOOTING INDEX.

Before performing symptom troubleshooting, check for
powertrain DTCs, R18A1 engine (see GENERAL
TROUBLESHOOTING INFORMATION ), K20Z3 engine
(see GENERAL TROUBLESHOOTING INFORMATION ).

2008 Honda Civic EX

2006-08 HVAC Heating/Air Conditioning - Civic (All Except Hybrid)

3. Connect the HDS to the DLC.
4. Turn the ignition switch ON (II).
5. Turn on the A/C on the HVAC control unit.
6. Check the FAN LOW CTRL in the PGM-FI Data List with the HDS.

Is the FAN LOW CTRL on?

YES - Go to step 7.

NO - Substitute a known-good ECM/PCM, R18A1 engine (see
SUBSTITUTING THE ECM/PCM ), K20Z3 engine (see SUBSTITUTING
THE ECM ), and retest. If the symptom/indication goes away with a known-
good ECM/PCM, replace the original ECM/PCM, R18A1 engine (see
ECM/PCM REPLACEMENT ), K20Z3 engine (see ECM
REPLACEMENT ).

7. Measure the voltage between the radiator fan relay 4P socket terminal No. 1

and body ground.

Fig. 44: Measuring Voltage Between Radiator Fan Relay 4P Socket
Terminal No. 1 And Body Ground

Is there battery voltage?

YES - Go to step 8.

NO - Replace the under-hood fuse/relay box (see REMOVAL AND
INSTALLATION ).

2008 Honda Civic EX

2006-08 HVAC Heating/Air Conditioning - Civic (All Except Hybrid)

8. Connect the radiator fan relay 4P socket terminals No. 1 and No. 2 with a

jumper wire.

Fig. 45: Connecting Radiator Fan Relay 4P Socket Terminals No. 1 And
No. 2 With Jumper Wire

Do the A/C condenser and radiator fans run on low?

YES - Go to step 9.

NO - Go to step 20.

9. Turn the ignition switch to LOCK (0).

10. Disconnect the jumper wire.
11. Turn the ignition switch ON (II).
12. Measure the voltage between the radiator fan relay 4P socket terminal No. 3

and body ground.

Fig. 46: Measuring Voltage Between Radiator Fan Relay 4P Socket
Terminal No. 3 And Body Ground

Is there battery voltage?

2008 Honda Civic EX

2006-08 HVAC Heating/Air Conditioning - Civic (All Except Hybrid)

YES - Go to step 12.

NO - Go to step 38.

13. Turn the ignition switch to LOCK (0).
14. Reinstall the radiator fan relay.
15. Jump the SCS line with the HDS.

16. Disconnect ECM/PCM connector A (44P).
17. Connect the ECM/PCM connector A (44P) terminal No. 4 to body ground with

a jumper wire.

Fig. 47: Connecting ECM/PCM Connector A (44P) Terminal No. 4 To
Body Ground With Jumper Wire

18. Turn the ignition switch ON (II).

Do the A/C condenser and radiator fans run on low?

YES - Check for loose wires or poor connections at ECM/PCM connector A
(44P) terminal No. 4. If the connections are good, substitute a known-good
ECM/PCM, and recheck. If the symptom/indication goes away, replace the
original ECM/PCM, R18A1 engine (see ECM/PCM REPLACEMENT ),

NOTE:

This step must be done to protect the engine control
module (ECM)/powertrain control module (PCM) from
damage.

2008 Honda Civic EX

2006-08 HVAC Heating/Air Conditioning - Civic (All Except Hybrid)