2008
5.7 all the bells and such except NAV.
About a month ago, I threw a P0646 code about the AC clutch not having sufficient voltage present.
Last week the fan refused to turn on and I actually had to roll the windows down to cool off. (Not good, as Ensenada, MX smells like poo!)
Within a few minutes, it turned on and resumed normal operation.
Today, while driving on the freeway, the fan starts cycling as if the power is being turned off while on high, then back on before it totally shuts off.
I could actually hear the fan struggling to stay on.
Again, throwing code 646.
Can anyone elaborate on what this code actually means?
Is it something that I might be able to address/repair myself?
P0646
Possible Causes
INTERNAL FUSED IGNITION SWITCH OUTPUT CIRCUIT
(C13) A/C CLUTCH RELAY CONTROL CIRCUIT OPEN
(C13) A/C CLUTCH RELAY CONTROL CIRCUIT SHORTED TO GROUND
A/C CLUTCH RELAY
PCM
Diagnostic Test
1. A/C CLUTCH RELAY OPERATION
Ignition on, engine not running.
With a scan tool, actuate the A/C Clutch Relay.
Is the A/C Clutch Relay operating?
Yes >> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No >> Go To 2
2. A/C CLUTCH RELAY RESISTANCE
Turn the ignition off.
Remove the A/C Clutch Relay from the IPM.
Measure the resistance of the A/C Clutch Relay Coil.
Is the resistance between 60 to 80 ohms?
Yes >> Go To 3
No >> Replace the A/C Clutch Relay.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
3. INTERNAL FUSED B+ CIRCUIT
Ignition on, engine not running.
Using a 12-volt test light connected to ground, probe the Internal Fused B+ circuit in the connection.
Does the test light illuminate brightly?
Yes >> Go To 4
No >> Repair the open or short to ground in the Internal Fused B+ circuit. Check and replace any open fuses.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
LX ENGINE ELECTRICAL DIAGNOSTICS 9 - 607
4. (C13) A/C CLUTCH RELAY CONTROL CIRCUIT OPEN
Turn the ignition off.
Disconnect the PCM harness connectors.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage
the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool
#8815 to perform
diagnosis.
Measure the resistance of the (C13) A/C Clutch Relay Control circuit from the relay connection to the appropriate
terminal of special tool
#8815 .
Is the resistance below 5.0 ohms?
Yes >> Go To 5
No >> Repair the open in the (C13) A/C Clutch Relay Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
5. (C13) A/C CLUTCH RELAY CONTROL CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (C13) A/C Clutch Relay Control circuit at the IPM.
Is the resistance below 5.0 ohms?
Yes >> Repair the short to ground in the (C13) A/C Relay Clutch Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No >> Go To 6
6. PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal
push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and
Ground circuits.
Were there any problems found?
Yes >> Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No >> Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
