P249E – Closed Loop Reductant Injection Control At Limit – Flow Too Low

What is Code P249E?

OBD-II diagnostic trouble code (DTC) P249E stands for "Closed Loop Reductant Injection Control At Limit – Flow Too High". This code indicates that the vehicle's selective catalytic reduction (SCR) system, which injects diesel exhaust fluid (DEF) to reduce NOx emissions, is operating at its maximum limit due to excessively high DEF flow.

Urgency and Severity

Code P249E itself is not extremely urgent and the vehicle can usually still be driven safely in the short term. However, it's important to diagnose and address the underlying issue promptly to prevent potential damage to the SCR system or catalytic converter. If the check engine light is flashing or other drivability issues are present, stop driving and have the vehicle towed to a dealer or qualified repair shop.

Applicability

P249E is a generic powertrain code that applies to many diesel vehicles equipped with SCR systems, including Ford, RAM, Nissan Titan XD, and some BMW models. The specific parts involved and diagnostic steps may vary somewhat between makes and models.

Parts Involved

The main components related to code P249E are:

• DEF injector: Sprays liquid DEF into the exhaust stream
• SCR catalyst: Converts NOx into harmless nitrogen and water using DEF
• DEF tank and lines: Store and supply DEF to the injector
• NOx sensors: Measure NOx levels before and after the SCR catalyst

Common Causes

Potential causes of excessive DEF flow and code P249E include:

• Clogged or failed DEF injector
• Contaminated or incorrect DEF fluid
• Leaking DEF tank or lines
• Faulty NOx sensor(s)
• SCR catalyst failure

Diagnosis

Key troubleshooting steps for code P249E:

1. Check DEF level and quality, replace if low or contaminated
2. Inspect DEF tank and lines for leaks, repair as needed
3. Test NOx sensors, replace if out of spec
4. Remove and clean DEF injector, replace if damaged
5. Evaluate SCR catalyst efficiency, replace if failed

Repair Costs

• DEF injector: $300-600 USD / €275-550 EUR + 1-2 hours labor
• SCR catalyst: $1500-3000 USD / €1400-2750 EUR + 3-6 hours labor

Prevention

To help avoid P249E and related SCR issues:

• Maintain proper DEF level and only use high-quality DEF fluid
• Address any DEF leaks immediately
• Have SCR system and sensors inspected regularly

Code P249E may appear in conjunction with other SCR-related DTCs like P1C54, P20EE, and P056D. Resolving those codes as well is important for proper emissions control and engine performance.

Frequently Asked Questions about P249E

What does OBD-II code P249E mean?

P249E stands for “Closed Loop Reductant Injection Control At Limit – Flow Too High”. It indicates the selective catalytic reduction (SCR) system is operating at maximum limit due to excessively high diesel exhaust fluid (DEF) flow.

How serious is code P249E? Is it safe to keep driving?

P249E is not extremely urgent, and you can usually continue driving safely in the short term. However, it’s best to diagnose and fix the underlying issue promptly to prevent potential SCR system or catalytic converter damage. If the check engine light is flashing or you notice drivability problems, stop driving and have the vehicle towed for repairs.

What vehicles can get code P249E?

Many diesel vehicles with SCR systems can experience P249E, including models from Ford, RAM, Nissan Titan XD, and some BMWs. The exact parts and diagnostic steps may differ slightly between makes.

What are the main components involved with P249E?

The key parts related to code P249E are the DEF injector, SCR catalyst, DEF tank and lines, and NOx sensors before and after the SCR catalyst.

What are the common causes of code P249E?

Potential causes include a clogged/failed DEF injector, contaminated/incorrect DEF fluid, leaking DEF tank or lines, faulty NOx sensor(s), and SCR catalyst failure.

How do you diagnose code P249E?

Key troubleshooting steps are:
1) Check DEF level and quality, replace if low or contaminated
2) Inspect for DEF leaks, repair as needed
3) Test NOx sensors, replace if out of spec
4) Clean DEF injector, replace if damaged
5) Evaluate SCR catalyst efficiency, replace if failed

How much does it cost to fix code P249E?

A DEF injector replacement typically costs $300-600 USD (€275-550 EUR) plus 1-2 hours labor. An SCR catalyst replacement is much more at $1500-3000 USD (€1400-2750 EUR) and 3-6 hours labor.

How can I prevent getting code P249E again?

To avoid repeat P249E issues:

• Maintain proper DEF level and use only high-quality DEF fluid
• Fix any DEF leaks immediately
• Have the SCR system and sensors inspected regularly

Can low DEF fluid cause code P249E?

Yes, low DEF level is one possible cause. The SCR system may overcompensate by injecting too much DEF when the fluid is low. Always keep the DEF tank adequately filled.

Can a bad DEF injector cause code P249E?

Definitely. A clogged or malfunctioning DEF injector can cause excessive DEF flow, triggering code P249E. The injector may need to be cleaned or replaced.

Can a faulty NOx sensor cause code P249E?

Yes, a bad NOx sensor can misread the exhaust NOx levels, making the SCR system inject too much DEF. Testing and replacing failed NOx sensors is an important troubleshooting step.

Can an SCR catalyst failure cause code P249E?

Yes, if the SCR catalyst is not working efficiently, the system may try to compensate by injecting excess DEF, leading to code P249E. A failed catalyst requires replacement.

Can contaminated DEF fluid cause code P249E?

Using contaminated, poor quality, or incorrect fluid in the DEF tank can definitely cause SCR system issues like code P249E. Always use a high-quality DEF fluid meeting ISO 22241 specifications.

Can a leaking DEF tank cause code P249E?

Yes, leaks in the DEF tank or lines can allow air into the system, causing erratic DEF injection and code P249E. Inspect for visible leaks and repair any that are found.

Can a software update fix code P249E?

Possibly. In some cases, a software update may be able to optimize the SCR system control parameters and resolve a P249E code. However, it’s more likely a hardware issue that requires physical repair.

Can code P249E cause limp mode?

Code P249E itself does not typically trigger limp mode. However, if the underlying issue is not resolved, it may eventually lead to SCR system failure and limp mode engagement to protect the engine.

Can code P249E cause other drivability symptoms?

You may notice a reduction in engine power or fuel efficiency due to the SCR system not operating optimally. The engine may also run rough or hesitate. The check engine light will be illuminated.

What other codes may appear with P249E?

Related SCR system codes that often appear alongside P249E include P20EE (NOx exceedance), P1C54 (SCR efficiency below threshold), and P056D (reductant quality too low). Diagnose and repair those issues as well.

Can you drive with code P249E permanently?

While it’s possible to keep driving with code P249E for a period of time, it’s not advisable long term. Excess DEF consumption can damage the SCR catalyst and cause the vehicle to fail emissions tests. Repair the underlying issue properly.

How often should the SCR system be inspected to prevent P249E?

Having the SCR system and sensors inspected at least once a year or every 30,000 km (18,000 miles) is a good preventative measure. Vehicles that experience frequent short trips or idle excessively may need more frequent checks.