01 Common Car Starting Issues and How to Troubleshoot Them • 02 Why Your Car Is Losing Coolant But No Leak and What Should … • 03 Fill Up Less, Drive More: The Complete Guide to Saving Fuel… • 04 This Simple Shortcut Many Drivers Take Often Ends In Engine… • 05 What’s That Noise? Diagnosing and Fixing Strange Engine Sou… • 06 Engineers Created Paint That Can Literally Generate Electri… • 07 Understanding Oxygen Sensors and Their Impact on Your Car • 08 Troubleshooting Your Refrigerator: A Comprehensive Guide • 09 Can You Jump-Start Any Large Truck with a Car? Yes, and Her… • 10 Here's Why Your Car Feels Sluggish Even With A Full Tank Of… •

DTC codes / Chrysler codes / P1531

P1531 · ChryslerA/C Low Side Temperature Sensor Fault

P1531 on Chrysler vehicles means the powertrain control module (PCM) has detected an out-of-range signal from the A/C low side temperature sensor, which monitors the temperature of the refrigerant leaving the evaporator. The PCM uses this input to protect the compressor from liquid slugging and to manage clutch cycling, so a faulty reading will set this code and may disable the air conditioning.

SystemPowertrain
Code typeChrysler specific
SeverityLow
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • Air conditioning may stop cooling or the compressor clutch may fail to engage
  • A/C compressor clutch may cycle rapidly or not engage at all
  • Often no symptoms besides the warning light, especially in mild weather
  • Intermittent cooling that works when the engine is cold but fades as it warms
  • Blower motor may run but the air never gets cold
  • On some models the radiator cooling fan may run continuously as a failsafe

Common causes, most likely first

  1. Failed A/C low side temperature sensor (thermistor) inside the evaporator housing
  2. Damaged or chafed sensor wiring harness near the evaporator or PCM
  3. Corroded or loose electrical connector at the sensor or PCM
  4. Open or shorted sensor circuit caused by moisture intrusion into the connector
  5. PCM internal fault misreading the sensor input (rare but documented on Chrysler PCMs)
  6. Low refrigerant charge altering the temperature the sensor sees and pushing the signal out of range

How to diagnose and fix it

  1. Connect a scan tool and read the A/C low side temperature sensor PID while watching for a stuck, erratic, or implausible value
  2. Visually inspect the sensor connector and harness for corrosion, chafing, or pushed-back pins
  3. Measure sensor resistance with a multimeter and compare to the Chrysler temperature-resistance chart for the ambient temperature
  4. Check for a low refrigerant charge with manifold gauges before condemning the sensor, since a low charge can skew the reading
  5. Backprobe the sensor signal and ground wires at the PCM to confirm the circuit is intact and the PCM is seeing the correct voltage
  6. Replace the A/C low side temperature sensor if resistance testing proves it is out of specification
  7. Clear the code and verify the A/C system operates normally through a full clutch cycle before returning the vehicle

Why this sensor fails before the A/C does

  • The A/C low side temperature sensor is a thermistor that lives in the coldest, wettest part of the evaporator housing, so moisture and thermal cycling kill it long before the compressor wears out.
  • A low refrigerant charge can mimic a failed sensor because the sensor reads a temperature that is too high or too low for the conditions, so always verify charge before replacing parts.
  • Chrysler PCMs on some models will default to a fixed compressor cycling strategy when this code sets, which is why drivers sometimes report the A/C works but feels weak rather than dead.
  • A chafed harness behind the glovebox or near the evaporator core is a common missed cause, especially after dashboard or heater core work.
  • Do not confuse this code with an evaporator temperature sensor code on other manufacturers; on Chrysler the low side sensor is a distinct input used for clutch protection.

Can I keep driving with P1531?

The vehicle remains safe to drive because this fault affects only the air conditioning system and does not impair engine operation. Avoid running the A/C until the fault is repaired, since a misreported temperature can cause the compressor to cycle abnormally and shorten its life.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Chrysler vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage