P0647 OBD-II Trouble Code: A/C Clutch Relay Control Circuit High

P0647 code definition

The P0647 trouble code identifies an issue with the A/C clutch relay control circuit

What the P0647 code means

The P0647 code is a generic OBD-II trouble code that detects a problem with the A/C (air conditioning) clutch relay control circuit. The A/C clutch relay control circuit sends information to the powertrain control module (PCM), and many other control modules, such as the anti-lock brake control module, traction control module, climate control module, and instrument panel control module. When the PCM or one of the other control modules identifies that the A/C clutch relay control circuit is malfunctioning, the P0647 code will be triggered.

What causes the P0647 code?

Some potential causes for the P0647 code include:

• Faulty A/C compressor control relay
• PCM has defective A/C compressor drivers
• In rare cases, malfunctioning CAN bus
• Damaged ground strap or ground wire in one of the control modules
• Damaged electrical components (such as wires and connectors) in the circuit or the controller area network (CAN) bus

What are the symptoms of the P0647 code?

The P0647 trouble code will usually be accompanied by the Check Engine Light being illuminated, and often the A/C climate control light will illuminate or flash as well. The air conditioning system in the vehicle may not work, or may not work well.

How does a mechanic diagnose the P0647 code?

The P0647 trouble code will be diagnosed using a standard OBD-II trouble code scanner. A trained technician will use the scanner to look at the freeze frame data to gather information about the code, and to look for any additional trouble codes that are detected. The codes should then be reset, and the vehicle will be restarted. If the code does not return, it was likely triggered erroneously, or represents an intermittent error.

If the P0647 trouble code does return, then the technician should begin with a visual inspection of all the electrical components associated with the A/C clutch relay control circuit. All of the wires, connectors, harnesses, and fuses should be inspected, and any that are damaged in any way should be replaced. The mechanic can then test the ground wires and ground straps to make sure that they are operating correctly.

Next, the mechanic can inspect the A/C compressor control relay, which is the most likely issue. If the relay is in working order, the technician may want to use a CAN scanner to help assess the control modules and search for errors.

After any component is replaced, the mechanic should reset the trouble codes and restart the vehicle before continuing the inspection and repairs. By doing this, the technician can guarantee that they know as soon as the issue causing the P0647 code has been properly addressed.

Common mistakes when diagnosing the P0647 code

The most commonly made error when diagnosing the P0647 code is the failure to properly comply with the OBD-II trouble code diagnosis protocol. The diagnosis protocol should be followed at all times, step by step, to ensure that all inspections and repairs are efficient and successful.

It is common for additional codes to be detected as a reaction to the P0647 code. If these other codes are addressed before the P0467 code is, then the corresponding inspections and repairs will be fruitless. Trouble codes should always be addressed in the order in which they appear.

How serious is the P0647 code?

A vehicle with a detected P0647 trouble code will still be drivable, though it is possible that the air conditioning system will not properly work. Like all trouble codes, the P0647 code should be addressed sooner rather than later.

What repairs can fix the P0647 code?

Some possible repairs for the P0647 trouble code include:

• Replacement of the A/C compressor control relay
• Updated control module drivers
• Replacement of the electrical components in the CAN bus or A/C control circuit
• Replacement of control module ground straps and ground wires
• In rare cases, replacement of CAN bus or control modules

Additional comments for consideration regarding the P0647 code

In many vehicles, an issue with the A/C clutch relay control circuit needs to be detected eight times before the P0647 trouble code will be stored.

Need help with a P0647 code?

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