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DTC codes / Chrysler codes / P1598

P1598 · ChryslerA/C Pressure Sensor Voltage Too High

P1598 on Chrysler vehicles means the air conditioning (A/C) pressure sensor is sending a voltage signal to the powertrain control module (PCM) that is higher than the sensor's designed range, typically above 4.5 volts. The PCM interprets this high voltage as an implausible pressure reading and sets the code to protect the A/C compressor from damage.

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

Symptoms you may notice

  • The A/C compressor clutch may not engage, resulting in no cold air from the vents.
  • The check engine light (malfunction indicator lamp) illuminates on the dashboard.
  • The A/C system may blow warm air even when the controls are set to maximum cold.
  • In some cases, the radiator cooling fan may run continuously because the PCM uses A/C pressure data for fan control.
  • Often no symptoms besides the warning light, especially if the ambient temperature is low and A/C demand is minimal.

Common causes, most likely first

  1. Faulty A/C pressure sensor sending an incorrect high-voltage signal.
  2. Damaged or chafed wiring in the sensor signal circuit, shorting to voltage.
  3. Corroded or loose electrical connector at the A/C pressure sensor.
  4. Open ground circuit for the A/C pressure sensor, causing the signal voltage to float high.
  5. PCM internal fault incorrectly reading or biasing the sensor signal.
  6. Overcharging of the A/C system causing actual pressure to exceed sensor range (less common).

How to diagnose and fix it

  1. Use a scan tool to read live data for the A/C pressure sensor voltage and compare it to expected values with the key on, engine off.
  2. Visually inspect the sensor connector and wiring for corrosion, damage, or loose pins, and repair as needed.
  3. Disconnect the sensor and measure reference voltage (typically 5 volts) and ground continuity at the harness connector.
  4. Check the sensor signal circuit for a short to voltage or an open circuit using a multimeter and wiring diagram.
  5. If wiring and connections are good, replace the A/C pressure sensor with a known-good unit and clear the code.
  6. Verify repair by clearing codes, running the A/C system, and confirming the sensor voltage reads within normal range on the scan tool.
  7. If the code persists after sensor replacement and wiring checks, diagnose the PCM and its connections before condemning it.

What Most Techs Miss on P1598

  • A chafed signal wire shorting to a nearby 12-volt source is a frequent cause that mimics a failed sensor, so always inspect the harness routing near hot or moving components.
  • The A/C pressure sensor on many Chrysler vehicles shares a 5-volt reference with other sensors; a short in one sensor can pull down the reference and set multiple codes, so check for companion codes.
  • A poor ground at the sensor can cause the signal voltage to float high, and simply cleaning the ground point often resolves the issue without parts replacement.
  • The PCM may set P1598 as a rationality check when the A/C system is overcharged, so verify system pressures with a manifold gauge set before replacing electrical parts.
  • Do not overlook the radiator cooling fan operation; a fan that runs constantly can indicate the PCM is acting on false high-pressure data from this sensor.

Can I keep driving with P1598?

You can generally drive the vehicle with P1598, but the A/C may not function and the compressor could be disabled to prevent damage. Avoid using the A/C system until the fault is repaired, and address the code promptly to prevent potential compressor or electrical damage.

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.

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