P05EB

What it means

P05EB means the engine control unit saw the exhaust temperature at the inlet of the SCR (selective catalytic reduction) NOx catalyst stay too low during the cold start warm-up phase. The catalyst needs a minimum temperature before urea dosing can start and NOx can be reduced properly. The exact temperature target and time limit depend on the vehicle and engine.

Symptoms

• Engine warning light on
• Possible SCR or exhaust emissions warning message on the dash
• Slow exhaust warm-up on cold starts, or the engine taking a long time to reach operating temperature
• Raised NOx emissions, which may show up at an emissions test
• Possible increase in fuel use if the engine is running extra warm-up measures
• Often no change in how the car drives

Possible causes

• Mainly short, cold-weather journeys that do not give the exhaust enough time to heat uplikely
• Engine running too cool, for example a thermostat stuck open or a coolant temperature sensor reading wronglylikely
• Faulty SCR inlet temperature sensor, or damaged wiring or connector giving a low or implausible readingpossible
• Exhaust leak or damaged insulation upstream of the SCR catalyst letting heat escape or giving false readingspossible
• Fault in the thermal management measures, such as a sticking intake throttle, EGR fault or injection problem that stops the exhaust warming up as plannedpossible
• Outdated engine control software calibration where the manufacturer has issued an update for this faultrare
• Degraded or contaminated SCR catalyst or exhaust component affecting heat-up (varies by model)rare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting ambient temperature, coolant temperature and journey length, and look for related coolant, temperature sensor, EGR or SCR codes.
2. Check for relevant technical service information or software updates for the specific model and engine.
3. Inspect the SCR inlet temperature sensor, its wiring and connector for damage, corrosion, water ingress or heat damage.
4. On a fully cold engine, compare live exhaust temperature sensor readings with coolant and ambient temperature; they should be similar and plausible.
5. Watch live data through a warm-up and check the engine reaches normal coolant temperature in a reasonable time; test the thermostat operation if it does not.
6. Check the exhaust system from the manifold to the SCR catalyst for leaks, cracks, loose joints or missing heat shielding.
7. Check the live status and operation of the actuators involved in warm-up, such as intake throttle, EGR valve and injection control, where the model supports it.
8. Check the vehicle's usage pattern with the owner, as mainly short trips can stop the exhaust warming up and set the code.

How to fix

• Replace the faulty SCR inlet temperature sensor, or repair the damaged wiring or connector.
• Replace a stuck-open thermostat or faulty coolant temperature sensor so the engine warms up normally.
• Repair exhaust leaks and replace missing or damaged exhaust heat insulation.
• Repair or replace any faulty warm-up related component found, such as a sticking throttle or EGR valve.
• Apply the manufacturer's updated engine control software where the fault is a known calibration issue.
• Advise regular longer drives so the exhaust reaches full operating temperature, then clear the code and confirm it does not return.

Can I keep driving?

Nearby codes

• P05EAGenericEngine Oil Bypass Valve Control Circuit High
• P05ECGenericCold Start Injection Timing Performance