P0645 OBD-II Trouble Code: A/C Clutch Relay Control Circuit

Our certified mechanics come to you · 12-month, 12,000-mile warranty

SCHEDULE P0645 DIAGNOSTIC Get a fair and transparent estimate upfront
Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0645 code

P0645 is a diagnostic trouble code (DTC) for "A/C Clutch Relay Control Circuit". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic for $70.00. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $30.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$70.00$30.00
Toyota$70.00$30.00
BMW$70.00$30.00
SCHEDULE P0645 DIAGNOSTIC Get a fair and transparent estimate upfront

check engine light

P0645 code definition

If your PCM has stored a P0645 code, it means that a problem has been identified in the A/C clutch relay control circuit.

What the P0645 code means

This code can be identified by the PCM, or by one of the following supporting modules:

  • Body control module
  • Alternative fuel control module
  • Cruise control module
  • Antilock brake control module
  • Fuel injection module
  • Instrument panel control module
  • Anti-theft module
  • Turbo control module
  • Traction control module
  • Climate control module
  • Cruise control module

If there is a fault in the A/C clutch relay control circuit, the system will record a trouble code, and your Check Engine Light will come on. This may not happen right away – with some vehicles, it can take as many as eight failures before the Check Engine Light is activated.

What causes the P0645 code?

Usually, the cause is a defective A/C compressor driver or A/C compressor control relay. Other causes could be:

What are the symptoms of the P0645 code?

You may not notice any symptoms other than an illuminated Check Engine Light. You could also see an illuminated or flashing A/C Malfunction light. If the Check Engine Light has not come on, the system may have stored the code as pending. If you are driving in hot weather, though, you may find that your air conditioning works poorly, if at all.

How does a mechanic diagnose the P0645 code?

The mechanic will use a code reader and ohmmeter in order to diagnose the code. Then, he or she will:

  • Visually examine all the connectors and wiring, and replace any that are shorted out, open, disconnected or otherwise damaged
  • Re-test the system to determine if the repairs have been effective
  • Clear out the codes and see if they return when the vehicle is operating
  • Test drive the vehicle
  • Possibly use a specialized scanner like an Autohex, because of the complexity of the wiring
  • Use a CAN scanner to identify pin values and determine how the control module is operating
  • Check for corroded or loose connectors that could be causing trouble codes to be stored
  • Compare findings with the manufacturer’s values

Frequently, a mechanic will simply replace an entire wiring harness rather than attempt to repair various components. This is because the diagnostics can be so complicated and time-consuming. A full replacement is often more cost-effective for the customer.

Common mistakes when diagnosing the P0645 code

The most common mistake when diagnosing the P0645 code is to misdiagnose the symptoms and codes. This is because of the complexity involved. Often, the wrong components are repaired or replaced.

How serious is the P0645 code?

That really depends on how much you value your air conditioning. Some drivers never use it, being content to just drive around with their windows down. For others, air is an absolute must. Suffice it to say, though, that this is not a problem that is ever going to endanger you or your passengers, so you can take your time having it dealt with, if you choose to deal with it at all.

What repairs can fix the P0645 code?

Corroded or otherwise damaged wires can be replaced, or if the source of the problem is not easily identifiable, the entire wiring harness can be replaced. Sometimes this is the more affordable option.

Need help with a P0645 code?

Having to do without air conditioning in your car is inconvenient. If you prefer to drive in comfort, and you’re A/C isn’t working properly, contact us at YourMechanic. You can reach us at 1-800-701-6230, or request an appointment using our online form. We will send a qualified mobile mechanic to the location of your choosing to fix you’re A/C. We’ll also be happy to provide you with a free quote.

trouble codes
Check Engine Light
P0645

Fast and easy Check Engine Light is on Inspection service at your home or office.

SCHEDULE P0645 DIAGNOSTIC
Get a fair and transparent estimate upfront

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.5/5

Number of Reviews

3,696

Rating Summary
3,372
162
42
24
96
3,372
162
42
24
96

Jerel

8 years of experience
125 reviews
Jerel
8 years of experience
Jarel is always very professional and gets the jobs done right. He's great about explaining what he's doing as he does it. I 100% recommend him
2006 FORD FOCUS - CHECK ENGINE LIGHT IS ON - RALEIGH, NORTH CAROLINA

Jose

13 years of experience
258 reviews
Jose
13 years of experience
Jose did a great job and I definitely would recommend this service.
2012 HONDA CIVIC - CHECK ENGINE LIGHT IS ON - OPA LOCKA, FLORIDA

Duane

22 years of experience
330 reviews
Duane
22 years of experience
Arrived on time and got to work immediately. Explained everything that he did after he was completed with the work. Answer all of my questions. Very professional.
2002 FORD ESCAPE - CHECK ENGINE LIGHT IS ON - OCEANSIDE, CALIFORNIA

Diego

18 years of experience
223 reviews
Diego
18 years of experience
Very professional. He explained what the problem may be and then confirmed it after testing the coil. I would definitely call him again and would recommend him to friends and family
2000 LEXUS ES300 - CHECK ENGINE LIGHT IS ON - SURPRISE, ARIZONA

More related articles

Symptoms of a Bad or Failing Flexible Clutch Hose
Common signs include difficulty shifting, low clutch fluid, and feeling no resistance at the clutch pedal.
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
The Traveler’s Guide to Driving in Malaysia
CraigBurrows / Shutterstock.com Malaysia is a popular destination for many tourists today. The country has amazing sights and attractions that you will want to explore....

Related questions

Q: P0843

Trouble code P0843 pops up quite frequently on vehicles such as your Honda CR-V. The 2nd clutch transmission pressure switch is installed in the hydraulic pressure circuit to the 2nd clutch. The Powertrain Control Module (PCM) uses this information to...

Q: I have the p10ED what is it

Although P10E(x) codes relates to problems with the Valvetronic gear (cam timing sensors and actuators), I am unable to find a P01ED code specifically. The computer will store information that can be read with a professional-level scanner to help pinpoint...

Q: I got a 05 pacifica and the head gaskets were bad so I changed them. I put it back together and changed oil and now it won't start.

Hi there. The codes are coming up for the Oxygen Sensor, Oil Pressure Sensor, Evaporative Emission System Vent Valve, and the Air Conditioning Clutch Relay. Since all of these conditions are separate circuits and in different locations, I suspect that...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1-800-701-6230 · hi@yourmechanic.com