P2520 code meaning
A/C Request A Circuit Low
What P2520 means
P2520 is set when the voltage on A/C request input A stays below the band the engine module accepts. Depending on whether the input is active-high or active-low, a grounded wire then reads as a permanent request or as none at all – either way the module distrusts it. Most often a harness rubbed through to body metal, a pinched wire behind the dashboard or a climate panel output stuck low is behind it. No maker publishes P2520 with thresholds; CARB only requires that A/C parts influencing fuel or spark control be checked, and on many cars with a networked request such as the 2011 Saab 9-5 the wired input does not exist. Unlike P2519 the circuit is not simply open, and P2521 is its high counterpart. The A/C may refuse to run or run unasked.
P2520 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2520
- A/C does not switch on, or compressor runs although A/C is off
- Idle speed behaves oddly when the A/C is toggled
Common causes of P2520
- Most likelyRequest wire shorted to ground
- PossibleClimate control output stuck low
- Less likelyEngine module input stage faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Ac request input aHvac module
What each part of P2520 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 20 | The exact fault in that area. |
What to do next
- Note P2520 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2520
What does P2520 mean?
P2520 means "A/C Request A Circuit Low". P2520 is set when the voltage on A/C request input A stays below the band the engine module accepts. It is a generic code, so it means the same on every make.
Is it safe to drive with P2520?
P2520 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P2520 fail an emissions test?
P2520 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P2520 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will P2520 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.