Open or shorted heater element inside the upstream oxygen sensor.; Damaged or corroded wiring harness between the oxygen sensor and the powertrain control module.; Blown fuse or faulty relay that supplies power to the oxygen sensor heater circuit.; Poor ground connection at the sensor or engine block.; Faulty powertrain control module driver for the heater circuit, though this is less common.; Aftermarket oxygen sensor with incorrect heater resistance.; Contamination or physical damage to the sensor causing heater failure.

DTC codes / Chrysler codes / P1031

P1031 · ChryslerHO2S Heater Current Monitor Control Circuit Sensors 1

Q: What does code P1031 mean?

HO2S Heater Current Monitor Control Circuit Sensors 1. P1031 on Chrysler vehicles indicates that the powertrain control module has detected an abnormal current flow in the heater control circuit for the upstream oxygen sensor on bank 1, sensor 1. The computer monitors the heater current to verify the sensor reaches operating temperature quickly, and this code sets when the current is outside the expected range during the heater test.

P1031 on Chrysler vehicles indicates that the powertrain control module has detected an abnormal current flow in the heater control circuit for the upstream oxygen sensor on bank 1, sensor 1. The computer monitors the heater current to verify the sensor reaches operating temperature quickly, and this code sets when the current is outside the expected range during the heater test.

SystemPowertrain

Code typeChrysler specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms.
Slightly higher fuel consumption because the oxygen sensor stays in open-loop longer than normal.
Occasional rough idle or hesitation when the engine is cold, as the sensor is not heated quickly.
A pending code or stored code that returns after clearing if the circuit fault is persistent.
In rare cases, a failed emissions test due to the sensor not being ready.

Common causes, most likely first

Open or shorted heater element inside the upstream oxygen sensor.
Damaged or corroded wiring harness between the oxygen sensor and the powertrain control module.
Blown fuse or faulty relay that supplies power to the oxygen sensor heater circuit.
Poor ground connection at the sensor or engine block.
Faulty powertrain control module driver for the heater circuit, though this is less common.
Aftermarket oxygen sensor with incorrect heater resistance.
Contamination or physical damage to the sensor causing heater failure.

How to diagnose and fix it

Inspect the oxygen sensor heater fuse and replace if blown, then recheck the circuit.
Disconnect the sensor and measure resistance across the heater terminals; compare to specification.
Check for battery voltage at the heater supply wire with the key on, engine off.
Inspect the wiring harness for chafing, corrosion, or loose connectors between the sensor and the PCM.
Perform a voltage drop test on the ground circuit to ensure a clean ground path.
If the circuit tests good, replace the upstream oxygen sensor with an OEM-quality part.
Clear the code and verify the repair by running the oxygen sensor heater monitor to completion.

Don't overlook the heater circuit fuse

A blown fuse for the oxygen sensor heater is a common cause that many technicians miss when they jump straight to replacing the sensor.
The PCM may set P1031 even if the sensor still works in closed loop, because the heater current test fails only during cold starts.
Aftermarket sensors often have different heater resistance and can trigger this code repeatedly even though they are new.
Corrosion inside the connector pins can increase resistance and cause the heater current to fall below the expected threshold.
A weak battery or charging system can cause the heater current to be low during the test, setting a false P1031.

Can I keep driving with P1031?

You can usually continue driving with P1031, but avoid extended idling and cold-start short trips until it is repaired. Prolonged driving with a failed heater can lead to higher emissions and eventually damage the catalytic converter.

Tools that help

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