AutoCodes – Generic – P0645

P0645 Code - Air Conditioning Clutch Relay Circuit Malfunction

Quick Answer

Battery positive voltage is supplied to the A/C compressor clutch relay. Common causes include Faulty Air Conditioning Clutch Relay, Air Conditioning Clutch Relay harness is open or shorted, Air Conditioning Clutch Relay circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0645 indicates Air Conditioning Clutch Relay Circuit Malfunction.
Common causes: Common causes include Faulty Air Conditioning Clutch Relay, Air Conditioning Clutch Relay harness is open or shorted, Air Conditioning Clutch Relay circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 41,866

How popular is this code, among other codes? Medium

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 13, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0645 Description

Battery positive voltage is supplied to the A/C compressor clutch relay. The Powertrain Control Module (PCM) controls the relay by grounding the control circuit through an internal solid-state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component on, the voltage of the control circuit should be near 0 volts. When the PCM is commanding the control circuit to a component off, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses a voltage other than what is expected, this Diagnostic Trouble Code (DTC) will set.

OBDII Code P0645 - Air Conditioning Clutch Relay Circuit Malfunction - AutoCodes.com — P0645 Code - Air Conditioning Clutch Relay Circuit Malfunction

What does this mean?

What are the Possible Causes of the DTC P0645?

Faulty Air Conditioning Clutch Relay
Air Conditioning Clutch Relay harness is open or shorted
Air Conditioning Clutch Relay circuit poor electrical connection
Faulty Powertrain Control Module (PCM)

How to Fix the DTC P0645?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0645 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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Need Help with the Code?

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Information for Specific Makes

P0645 Audi — A/C Clutch Relay Control Circuit
P0645 BMW — Air Conditioning Copmressor Activation
P0645 Buick — Air Conditioning Compressor Clutch Relay Control Circuit
P0645 Cadillac — Air Conditioning Compressor Clutch Relay Control Circuit
P0645 Chevrolet — Air Conditioning Compressor Clutch Relay Control Circuit
P0645 Chrysler — Air Conditioning Clutch Relay Circuit Malfunction
P0645 Dodge — Air Conditioning Clutch Relay Circuit Malfunction
P0645 Ford — Air Conditioning Clutch Relay Circuit Malfunction
P0645 GMC — Air Conditioning Compressor Clutch Relay Control Circuit
P0645 Hummer — Air Conditioning Clutch Relay Control Circuit
P0645 Hyundai — A/C Clutch Relay Control Circuit
P0645 Jeep — Air Conditioning Clutch Relay Circuit Malfunction
P0645 KIA — Air Conditioning Clutch Relay Circuit Malfunction
P0645 Lincoln — Air Conditioning Clutch Relay Circuit Malfunction
P0645 Mazda — Air Conditioning Clutch Relay Circuit Malfunction
P0645 Mercury — Air Conditioning Clutch Relay Circuit Malfunction
P0645 MINI — Air Conditioning Copmressor Activation
P0645 Mitsubishi — A/C Clutch Relay Circuit
P0645 Pontiac — Air Conditioning Clutch Relay Control Circuit
P0645 Saturn — Air Conditioning Clutch Relay Control Circuit
P0645 Suzuki — Air Conditioning Clutch Relay Circuit Malfunction
P0645 Volkswagen — A/C Clutch Relay Control Circuit

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0645 Code

1. What are the common symptoms of OBDII code P0645 related to the Air Conditioning Clutch Relay Circuit Malfunction?

The common symptoms include the air conditioning system not functioning properly, the AC compressor not engaging, and the AC light on the dashboard illuminating.

2. What are the possible causes of OBDII code P0645?

The possible causes include a faulty air conditioning clutch relay, a damaged wiring harness related to the relay circuit, a defective AC pressure switch, or a problem with the PCM (Powertrain Control Module).

3. How can I diagnose the issue causing OBDII code P0645?

You can diagnose the issue by using a diagnostic scanner to read the code, checking the condition of the air conditioning clutch relay, inspecting the wiring for any damage, and testing the AC pressure switch for proper functionality.

4. Can a malfunctioning air conditioning clutch relay impact the overall vehicle performance?

Yes, a malfunctioning air conditioning clutch relay can impact the overall vehicle performance by causing the AC system to not function properly, leading to discomfort in hot weather and potentially affecting engine performance due to increased load on the engine.

5. Is it safe to continue driving with OBDII code P0645 present?

It is generally safe to drive with this code present, but it is recommended to address the issue promptly to ensure the proper functioning of the air conditioning system and prevent any potential long-term damage.

6. How can I repair OBDII code P0645 related to the Air Conditioning Clutch Relay Circuit Malfunction?

You can repair this issue by replacing the faulty air conditioning clutch relay, repairing any damaged wiring, checking and replacing the AC pressure switch if necessary, and clearing the trouble code with a diagnostic scanner.

7. Are there any preventive measures to avoid encountering OBDII code P0645 in the future?

Regularly inspecting and maintaining the air conditioning system, checking the condition of the relay and wiring, and addressing any issues promptly can help prevent the recurrence of OBDII code P0645.

8. Can a DIY enthusiast fix OBDII code P0645 or is professional help recommended?

A DIY enthusiast with knowledge of automotive electrical systems and access to the necessary tools can attempt to fix OBDII code P0645. However, if unsure or uncomfortable with the repair process, seeking professional help is recommended.

9. Will resetting the trouble code resolve OBDII code P0645 permanently?

Resetting the trouble code may temporarily clear the warning light, but it will not fix the underlying issue causing OBDII code P0645. It is essential to diagnose and repair the root cause of the problem to prevent the code from reoccurring.

10. How long does it typically take to repair OBDII code P0645?

The repair time for OBDII code P0645 can vary depending on the specific cause of the issue, the availability of replacement parts, and the individual's expertise. On average, the repair can take anywhere from 1 to 3 hours to complete.