Aged or contaminated rear oxygen sensor (HO2S22) that no longer switches quickly; Exhaust leak between the catalytic converter and the sensor, or a cracked converter housing; Damaged or corroded sensor wiring or connector pins at the HO2S22 harness; A failing catalytic converter that no longer stores oxygen, causing the rear sensor to read lean; An intake air leak or unmetered air entering after the mass airflow sensor, skewing fuel trims; Low fuel pressure or a weak fuel pump delivering less fuel than the computer commands; A stuck-open purge valve or evaporative emissions fault allowing extra air into the intake

DTC codes / Jaguar codes / P1157

P1157 · JaguarLack Of HO2S22 Switches Sensor Indicates Lean

Q: What does code P1157 mean?

Lack Of HO2S22 Switches Sensor Indicates Lean. P1157 on a Jaguar means the rear heated oxygen sensor on bank 2 (HO2S22) is not switching between rich and lean as the engine computer expects, and the signal is stuck indicating a lean condition. The engine control module monitors the sensor's voltage and flags this code when the sensor fails to cross the lean-to-rich threshold within a calibrated time, which usually points to a lazy sensor, a wiring fault, or an exhaust leak ahead of the sensor.

P1157 on a Jaguar means the rear heated oxygen sensor on bank 2 (HO2S22) is not switching between rich and lean as the engine computer expects, and the signal is stuck indicating a lean condition. The engine control module monitors the sensor's voltage and flags this code when the sensor fails to cross the lean-to-rich threshold within a calibrated time, which usually points to a lazy sensor, a wiring fault, or an exhaust leak ahead of the sensor.

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 rough idle or hesitation when the engine is cold
Poor fuel economy as the computer adds fuel based on the false lean signal
A faint rotten-egg or fuel smell from the exhaust in some cases
Intermittent misfire or stumble under light acceleration

Common causes, most likely first

Aged or contaminated rear oxygen sensor (HO2S22) that no longer switches quickly
Exhaust leak between the catalytic converter and the sensor, or a cracked converter housing
Damaged or corroded sensor wiring or connector pins at the HO2S22 harness
A failing catalytic converter that no longer stores oxygen, causing the rear sensor to read lean
An intake air leak or unmetered air entering after the mass airflow sensor, skewing fuel trims
Low fuel pressure or a weak fuel pump delivering less fuel than the computer commands
A stuck-open purge valve or evaporative emissions fault allowing extra air into the intake

How to diagnose and fix it

Scan all modules and record freeze-frame data for P1157, then check for related codes in engine, transmission, and evap systems
Inspect the HO2S22 sensor, its connector, and the exhaust pipe for leaks, corrosion, or physical damage
Use a scan tool to watch HO2S22 voltage in real time; a healthy rear sensor should switch between roughly 0.1 V and 0.9 V
Check fuel trims and compare bank 1 and bank 2 rear sensor activity to isolate whether the fault is sensor-specific or system-wide
Perform a smoke test on the intake and exhaust to find unmetered air or leaks ahead of the sensor
Verify fuel pressure and injector operation if trims suggest a lean condition across both banks
Replace the HO2S22 sensor only after wiring and exhaust checks pass, then clear codes and confirm the monitor completes

Why a lazy rear sensor fools the computer

A rear oxygen sensor that switches slowly can set P1157 without any driveability complaint, so many owners replace good sensors when the real fault is a small exhaust leak at the converter flange.
Jaguar's rear sensor monitors are sensitive to exhaust leaks after the catalytic converter, and a pinhole leak in the pipe or a failed gasket can mimic a lean sensor signal.
The code does not always mean the sensor is dead; a contaminated sensor from coolant or oil burning in the engine can switch lazily and trigger P1157 while still producing a plausible voltage.
Bank 2 on V6 and V8 Jaguars is often the harder side to access, and technicians sometimes replace the sensor without checking the connector for green corrosion that causes the same symptom.
A failing catalytic converter can cause the rear sensor to read lean because the converter no longer stores oxygen, so always compare front and rear sensor switching before condemning the sensor.

Can I keep driving with P1157?

You can usually drive the car short distances to a workshop, but avoid heavy acceleration and long trips because the false lean signal makes the computer add fuel, which can overheat the catalytic converter and worsen fuel economy. If the check engine light starts flashing or the engine misfires, stop driving and have it towed.

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 Jaguar vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.