Case Study
BMW 320D Intermittent EML
Our customer's BMW 320d was booked in for an MOT, diagnostics and a major service. The diagnostics were for an intermittent engine management light (EML), along with a lack of power warning. The light would appear randomly when driving at lower speeds and, once on, would stay on until the engine was switched off and restarted. Our BMW specialist technicians set out to find the cause.
40E9 | 4B81 | 4C9E | BMW | EGR Valve Sticking | Engine Management Light | Lack of Power
Fault Codes
40E9 – Exhaust gas position controller, position control
4C9E – EGR valve plausibility
4B81 – EGR rate control deviation
Common Symptoms
- Engine management light coming on intermittently
- Lack of power warning
- Fault appearing at lower speeds
- Light staying on until the engine is restarted
BMW 320d Diagnostics
As the fault wasn't constant, our first step was to understand exactly when it happened, and the best person to tell us that is the car's main driver. Once we had replicated the EML coming on, we scanned the BMW for fault codes and found 40E9, 4C9E and 4B81, all pointing to the EGR system. The serial data showed the EGR valve wasn't reaching its desired position. A visual inspection revealed no obvious issues, and there were no relevant technical service bulletins. We then operated the EGR valve remotely and removed its cover, which revealed the mechanism was sticking. We checked the EGR cooler rod hadn't seized, confirming the EGR valve itself was faulty. Before reporting back, we also removed the MAP sensor to check whether it, or the rest of the intake system, was clogged with carbon deposits, and found it wasn't.
Vehicles Affected
BMW 3 Series
- BMW 3 Series 2007
- BMW 3 Series 2008
- BMW 3 Series 2009
- BMW 3 Series 2010
- BMW 3 Series 2011
- BMW 3 Series 2012
- BMW 3 Series 2013
- BMW 3 Series 2014
BMW 1 Series
- BMW 1 Series 2007
- BMW 1 Series 2008
- BMW 1 Series 2009
- BMW 1 Series 2010
- BMW 1 Series 2011
- BMW 1 Series 2012
- BMW 1 Series 2013
BMW 5 Series
- BMW 5 Series 2010
- BMW 5 Series 2011
- BMW 5 Series 2012
- BMW 5 Series 2013
- BMW 5 Series 2014
Sticking EGR Valve
With the sticking EGR valve confirmed and the rest of the intake system clear of excessive carbon, the only repair needed was a new EGR valve, fitted and initialised to the vehicle. We gave our customer a detailed estimate and a clear explanation of what was required, along with why it's important to replace a sticking EGR valve and the problems that can follow if it's left, such as reduced performance, higher emissions and further strain on the engine.
Resolution
By taking the time to understand when the fault happened and carrying out thorough checks, we were able to pinpoint the sticking EGR valve as the cause of the intermittent EML and lack of power, without our customer paying for unnecessary parts. Replacing and initialising the EGR valve resolves the fault and restores the 320d's performance.
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