P046A

What it means

P046A means the engine control unit compared the two catalyst temperature sensors on bank 1 and found their readings do not agree in the way it expects. It sets when the temperature difference across the catalyst, or the way the two readings change together, is outside the programmed range. Sensor position and the exact test logic depend on the model and engine, so check the manufacturer's data for the vehicle.

Symptoms

• Engine management light on
• Reduced power or limp mode on some models
• Poor fuel economy
• Particulate filter regeneration attempted more often or not completing, where fitted
• Possible failed emissions test

Possible causes

• Faulty or drifting catalyst temperature sensor 1 or 2 on bank 1likely
• Damaged, chafed or corroded sensor wiring or connector, including heat damage near the exhaustlikely
• Exhaust leak near the sensors giving false temperature readingspossible
• Degraded or blocked catalyst or filter changing the normal temperature patternpossible
• Sensor loose, wrongly fitted or in the wrong position after previous exhaust workpossible
• Engine misfire or rich or lean running altering exhaust temperaturespossible
• Control unit fault or outdated calibration where the manufacturer lists it as a known causerare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting engine load, speed and coolant temperature when the fault set
2. Check for related codes such as misfire, fuel trim, sensor circuit or particulate filter codes, and deal with those first
3. Visually inspect the sensors, wiring and connectors on bank 1 for heat damage, chafing, corrosion and a secure fit
4. Inspect the exhaust for leaks, cracks and loose joints around the catalyst and both sensors
5. Compare live data from both temperature sensors on a cold engine; they should start close together and read plausibly
6. Watch both readings as the engine warms and under load, checking that the sensor downstream follows the upstream one sensibly
7. Check the sensor circuits for resistance, supply and signal against the manufacturer's specification
8. Check for a technical bulletin or calibration update for the vehicle, and judge the catalyst condition using the manufacturer's procedure

How to fix

• Replace the faulty catalyst temperature sensor with a correct specification part
• Repair or replace damaged wiring or connectors, and secure the harness away from heat sources
• Repair exhaust leaks and refit the sensors correctly
• Fix any misfire or fuelling fault that is affecting exhaust temperatures
• Replace the catalyst or filter if testing shows it is degraded or blocked
• Apply a manufacturer calibration update only if it is documented as the cure for this fault

Can I keep driving?

Nearby codes

• P0469GenericEVAP Purge Flow Sensor Circuit Intermittent
• P046BGenericCatalyst Temperature Sensor 1/2 Correlation Bank 2