Failed oxygen sensor heater element (open circuit inside the sensor); Damaged or corroded wiring harness between the ECM and the O2 sensor heater circuit; Blown fuse or faulty relay supplying power to the O2 sensor heater; Loose or corroded connector pins at the O2 sensor or ECM; Internal hardware fault within the ECM heater driver circuit; Aftermarket O2 sensor with incorrect heater resistance; Rodent damage to the heater circuit wiring

DTC codes / Jaguar codes / P1185

P1185 · JaguarO2 Sensor Heater Circuit Open, Hardware Fault

Q: What does code P1185 mean?

O2 Sensor Heater Circuit Open, Hardware Fault. P1185 on a Jaguar means the engine control module (ECM) has detected an open circuit or internal hardware fault in the heater element of an oxygen (O2) sensor. The ECM commands the heater on and monitors the current flow; when the expected current is absent or the driver circuit itself fails, this code is stored.

P1185 on a Jaguar means the engine control module (ECM) has detected an open circuit or internal hardware fault in the heater element of an oxygen (O2) sensor. The ECM commands the heater on and monitors the current flow; when the expected current is absent or the driver circuit itself fails, this code is stored.

SystemPowertrain

Code typeJaguar specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Slightly higher fuel consumption during cold starts because the sensor takes longer to reach operating temperature
Occasional rough idle or hesitation when the engine is cold
In some cases, a stored pending code without the light being on
Emissions test failure due to the heater monitor not completing

Common causes, most likely first

Failed oxygen sensor heater element (open circuit inside the sensor)
Damaged or corroded wiring harness between the ECM and the O2 sensor heater circuit
Blown fuse or faulty relay supplying power to the O2 sensor heater
Loose or corroded connector pins at the O2 sensor or ECM
Internal hardware fault within the ECM heater driver circuit
Aftermarket O2 sensor with incorrect heater resistance
Rodent damage to the heater circuit wiring

How to diagnose and fix it

Check the O2 sensor heater fuse and relay, replacing any blown fuse or faulty relay
Inspect the O2 sensor connector and wiring for corrosion, chafing, or rodent damage
Measure the resistance of the O2 sensor heater element with a multimeter and compare to specification
Back-probe the heater circuit at the ECM to verify power and ground with the key on and engine off
Perform a voltage drop test on the heater circuit while the heater is commanded on
If the circuit and sensor test good, substitute a known-good O2 sensor to rule out an intermittent heater fault
If all external checks pass, diagnose the ECM driver circuit or replace the ECM as a last resort

Heater circuit checks before sensor replacement

A common mistake is replacing the O2 sensor without first checking the heater fuse and relay, which are often the real cause of an open circuit code.
The heater element can test good at room temperature but open up when hot, so a resistance check on a cold sensor may not reveal the fault.
Corroded pins at the O2 sensor connector are a frequent cause on older Jaguars, especially in damp climates, and are easily overlooked.
P1185 can be set by a poor ground connection at the engine block or chassis, which affects the heater circuit return path.
Some aftermarket O2 sensors have heater resistances that are out of specification, causing the ECM to set this code even though the sensor appears to function.

Can I keep driving with P1185?

You can usually continue driving with P1185 because the engine will still run, but the O2 sensor may take longer to warm up, increasing emissions and fuel consumption when cold. Avoid long periods of idling from a cold start and have the fault repaired before an emissions test.

Tools that help

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