Evaporator temperature sensor faulty or failed open circuit; Unplugged, corroded or loose sensor connector; Open circuit or chafed wiring in the signal or ground wire between the sensor and the control module; Poor sensor ground connection raising the signal voltage; Signal wire shorted to a voltage supply; Fault inside the control module that reads the sensor.

P1533

A/C Evaporator Temperature Sensor Circuit High Voltage.

Oldsmobile
Powertrain
Manufacturer code
Low severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
5: AreaVehicle speed, idle control and auxiliary inputs
33: FaultThe specific fault in that area

What it means

On Oldsmobile models, P1533 means the engine or climate control module saw a voltage that was too high on the A/C evaporator temperature sensor circuit. A high voltage reading usually points to an open circuit, a sensor that has failed open, or a poor connection, because the sensor signal rises when resistance becomes very high. The module can no longer judge evaporator temperature properly, so it may limit or stop A/C compressor operation.

Symptoms

A/C blows warm or does not cool properly
A/C compressor does not engage or cycles erratically
A/C or service light on the dash or a stored fault in the climate system
Evaporator freezing up and airflow dropping, if the compressor runs without proper control
Engine warning light on in some cases

Possible causes

Evaporator temperature sensor faulty or failed open circuitlikely
Unplugged, corroded or loose sensor connectorlikely
Open circuit or chafed wiring in the signal or ground wire between the sensor and the control modulelikely
Poor sensor ground connection raising the signal voltagepossible
Signal wire shorted to a voltage supplypossible
Fault inside the control module that reads the sensorrare

How to diagnose

Read all stored codes and freeze frame data, and note whether the fault is current or intermittent before clearing anything
Visually inspect the evaporator sensor connector and the wiring along its run for damage, corrosion, rubbing or pushed-out terminals
With the sensor connected, view the evaporator temperature value on a scan tool and compare it with the likely actual temperature; a very low or extreme reading suggests an open circuit
Unplug the sensor and measure its resistance, then compare it with the specification for the model, as values vary by sensor type
Check the reference voltage and ground at the sensor connector against the wiring diagram for the specific model
Wiggle test the harness and connector while watching the live reading for dropouts
Test the signal wire for continuity to the module and for a short to voltage, with the module and sensor unplugged
If wiring and sensor are proven good, check module power, grounds and connector condition before suspecting the module

How to fix

Replace the evaporator temperature sensor if its resistance is out of specification or open
Clean, repair or replace the damaged connector or terminals
Repair or replace open, chafed or shorted wiring in the sensor circuit
Restore a poor ground connection in the sensor circuit
Replace or repair the control module only after the circuit and sensor have been fully proven good

Can I keep driving?

Low severity

The car can normally be driven as the fault mainly affects the A/C. Book it in for repair, and avoid running the A/C if the evaporator is icing up or airflow drops.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.