Guide To P2521 OBD Error Code Solutions

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The trouble code P2521 can be explained as A/C Request "A" Circuit High. This diagnostic fault code is a generic powertrain code, which means that it would apply to the OBD-II equipped vehicles. The specific repair steps can vary as it depends upon the vehicle make and model. The engine control module, powertrain control module or the transmission control module monitors this circuit depending upon the particular automobile.

If the engine control module would detect a variation in the voltage coming from the refrigerant pressure through the air conditioning (A/C) pressure sensor that is outside the parameters set by the automobile manufacturer, then it would store the P2521 error code. This would also give rise to the illumination of the check engine light.

What causes this problem with the A/C Request "A" Circuit High?

• The refrigerant might be low
• Excessive much refrigerant
• Some issues related to the low side pressure sensor
• Unlocked low side pressure sensor harness
• Unsatisfactory electrical connection in the low side pressure sensor circuit

1. A/C compressor - Most of the people are not aware that the premature wear or damage to the compressor and compressor belts might result in the failure of the AC compressor. It would be nice if you get it replaced on time.
2. Engine Control Module - If there is any corrosion or breaks in the internal wiring of the harness, then it can cause a short in the ECM or can also cause corrosion in the ECM through the wiring harness. You can always rely on us as we have the best auto parts for our customers.
3. Powertrain Control Module - The onboard computer, or powertrain control module is the brain of the engine control system. Now if the brain is not working properly, then neither is the car engine. Get it replaced before the situation gets worse.
4. Electronic Control Unit - Is your car jump starting on reverse polarity? Or are you facing some intermittent starting issues? If yes, then it indicates that your electronic control unit is bad. So it is very important to replace the defective electronic control unit with us at equitable prices.
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There could be countless symptoms that would accompany this fault code. Willing to know some common symptoms of OBD Trouble Code P2521? Your wish is our demand. Have a look at them below:

Common Symptoms

• Check engine light might come into signal

Looking out for some ways with the help of which you can correct this fault code? Then you have arrived at the correct place. We are here to help you out, so you must check out the steps mentioned below as follows:

• It is essential to restore the flawed A/C compressor switch
• Rehabilitate the defaults in the wiring or connectors
• You must fix the defective high pressure switch
• Make sure to add refrigerant
• Carefully adjust the faults in the A/C refrigerant pressure sensor
• Recondition the leaks in the system

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It is essential to diagnose this fault code. Here are some steps which a mechanic should follow for diagnosing the problem that triggered a P2521 code to be stored:

• The mechanic or the technician will use a diagnostic scanner or code reader like DVOM to visually scan for the error codes in the vehicle.
• The average automotive AC system utilizes between one and four refrigerant pressure switches so that it can provide safe and efficient operation.
• Freon is utilized to distribute oil throughout the air conditioning system, so you can see that refrigerant pressure is crucial to a/c system longevity and operation.
• The pressure switches can be threaded onto metal a/c lines or inserted into the compressor.
• These switches are generally of a pressure sensitive "ON/OFF" design.
• Now as the pressure would rise in the a/c system it would press against spring tension in the low pressure switch.
• When sufficient pressure is reached for proper system operation, then the contacts which are inside of the switch would be closed and the compressor clutch electrical circuit is completed, thus it would allow the clutch to engage.
• The high pressure switches would operate in the same manner.
• When system pressure would become excessive, then it would press against spring tension inside the switch.
• When system pressure reaches a level that could be detrimental to the compressor and other major components, contacts inside the switch are opened and the electrical circuit for the a/c compressor is opened, which would cause the a/c clutch to disengage.
• Repeated failures (usually 3) of this nature are recorded by the powertrain control module.
• After a predetermined number of failure cycles would be completed, then this error code would be stored and there would be an illumination in the service engine soon lamp.
• Some models also disable the a/c compressor clutch until the code has been cleared. Several tools would be required to successfully diagnose this fault code.
• This is a general type of error code which is diagnosed with the help of a scanner.
• The mechanic will insert a scanner to diagnostic port of the vehicle and recover the codes and freeze frame data.
• If he happens to find any additional error codes, he has to address them as well.
• Once it is done, he has to reset the vehicle, and then test drive to see if the error code appears.
• If the error code does not return, then there can be an erratic condition.
• Then the mechanic has to check the wires, connectors and other electrical components and quickly replace them if he finds them to be damaged or defective.
• Make sure to retest the system after repairs are completed to ensure success. If all system wiring, connectors, and components appear to be in good working condition, connect the scanner (or code reader) to the diagnostic connector.
• Then the freeze frame data should be recorded. This information would be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored.
• You should continue by clearing the code and operating the vehicle to see if it returns.
• This will help to determine whether or not the malfunction is intermittent
• Now once all the codes are cleared, then you should test drive the vehicle to see if the code returns.
• If the code fails to immediately return, then it is an indication that you have an intermittent condition.
• Intermittent conditions can prove to be quite challenging to diagnose and in extreme cases it should be allowed to worsen before a right diagnosis can be made.
• Connect the scanner or code reader and then record all stored trouble codes as well as freeze frame data.
• All the codes should be cleared up, then connect the a/c gauges, carefully start the car engine and then turn the a/c on high.
• The pressure gauge readings should be observed carefully.
• If the low pressure gauge reading drops below 29 psi, and compressor clutch engagement is disabled, suspect a low freon condition.
• Slowly add freon until the low pressure reading is approximately 35 psi (monitor high side pressure as well - it should maintain around 225 psi).
• If the compressor clutch is engaged and the a/c system begins to cool normally, check for leakage in the freon and then it should be repaired as per the requirement.
• If system pressure exceeds the manufacturer's minimum specifications (usually 30 psi) and the compressor clutch fails to engage, then it would indicate that there are some faults in the low refrigerant pressure sensor.
• Check for voltage and ground signals at the low pressure switch electrical connector.
• Compare your actual findings with manufacturer's specifications and repair open or shorted circuits as needed
• If voltage and ground signals coincide with the specifications set by the manufacturer, then test the low pressure switch resistance utilizing the digital volt/ohmmeter.
• Compare your findings to the specifications set by the manufacturer and replace the switch as per the requirement.
• Then all the codes should be cleared up, connect the a/c gauges, start the engine and turn the a/c on high.
• The readings of the pressure gauge should be carefully observed.
• If the high pressure gauge reading exceeds the manufacturer's maximum specification (usually 275 to 300 psi), turn the a/c system off and the pressure should be allowed to decrease.
• Turn the a/c back on and observe the electric condenser fan (if so equipped) operation.
• If the electric cooling/condenser fan/s are not working, diagnose the cause of this issue.
• Lack of electric cooling/condenser fan operation will cause high pressure to soar.
• If the fan is working and a/c system pressure exceeds maximum recommended specs, suspect a restriction in the orifice, expansion valve, accumulator, receiver dryer, or condenser. If the high pressure reading is within specs and the compressor clutch fails to engage due to a high pressure condition, perform a resistance test on the high pressure switch and compare your findings with manufacturer's specifications.
• Restore the high pressure switch as required
• If the switch does fall within acceptable specifications, examine continuity in the system circuit
• Repair or replace defective electrical wiring and connectors as per the requirement. If a/c refrigerant pressure switches and circuitry fail to yield the cause of this malfunction, suspect a quirky climate control head or a/c compressor switch
• Check the unit according to specifications set by the manufacturer and replace components as needed.

Common Mistakes When Diagnosing The P2521 Code

• Malfunctioning A/C compressor relay
• There can be a failure in the A/C compressor
• There might be a failure in the powertrain control module
• Wiring problems