In this post, we will cover several common fault codes for the BMW N54 twin turbo engine. These codes apply to the 135i, 1M, 335i, 535i, X6 and Z4 powered by the N54. Additionally, certain fault codes may apply to various non-N54 engines.
*Use control F to search for a specific fault code.
BMW N54 Misfire Fault Codes
When the N54 misfires it will generally throw a fault code. Different codes exist for each cylinder so you can identify exactly where the misfire is occurring. Below is a list of the various N54 misfire faults:
- 29CD (10701) - Misfire cylinder 1
- 29CE (10702) - Misfire cylinder 2
- 29CF (10703) - Misfire cylinder 3
- 29D0 (10704) - Misfire cylinder 4
- 29D1 (10705) - Misfire cylinder 5
- 29D2 (10706) - Misfire cylinder 6
- 29D9 (10713) - Misfire due to low fuel
N54 Misfire Fault Code Causes
Fortunately, misfire codes on the N54 are generally an easy fix. Quite a few various underlying issues may cause N54 misfire codes. However, the three main culprits, in order from most to least likely, are:
**Check for other fault codes that may be appearing, too. For example, misfire codes coupled with fueling related codes may indicate an issue within the fueling system.
Spark plugs are the most common cause of misfire codes on the N54. On tuned and modified N54's, it's not uncommon for spark plugs to go bad after a mere 15,000 miles. As spark plugs wear down they become less effective at generating a spark. If the spark isn't able to fully ignite the air/fuel mixture then you will experience misfires. The same applies to ignition coils, however they typically last roughly twice as long as spark plugs. Finally, fuel injectors are a known problem on N54 engines. Leaky or faulty injectors may cause misfire codes, too.
However, how do you narrow the problem and figure out what is causing the N54 to misfire?
Locating Cause of N54 Misfire Codes
As an example, assume you have code 29CD - misfire on cylinder 1. Ignition coils sit atop the spark plugs and will be the easiest component to switch. As such, take the ignition coil from cylinder 1 (the misfiring cylinder) and swap it with the cylinder 2 ignition coil. If your N54 now throws code 29CE - misfire cylinder 2 - there you have it. The cylinder 1 ignition coil, now on cylinder 2, is at fault.
If code 29CD remains (misfire cylinder 1) you have essentially eliminated the possibility of a faulty ignition coil. Now, you will want to repeat the process with the spark plugs. Swap the cylinder 1 spark plug to cylinder 2. If the misfire follows you've got a problem with the spark plugs. If it remains on cylinder 1 then, unfortunately, the problem isn't so straight forward.
**If a single spark plug or ignition coil is causing the issue, we highly recommend replacing all 6. Especially if the plugs and/or coils are older.
BMW N54 Fueling Fault Codes
In this section, we'll break down a few various fueling related codes. This includes codes related to the N54's HPFP, LPFP, fuel injectors, fuel rail, and fuel sensors.
- 29DC (10716) - Cylinder Injection Switch-off
- 29E0 (10720) - Fuel Mixture Control 1 (bank 1, cylinders 1-3)
- 29E1 (10721) - Fuel Mixture Control 2 (bank 2, cylinders 4-6)
- 29E2 (10722) - Fuel Injection Rail, Pressure Sensor Signal
- 29F3 (10739) - Fuel Pressure Sensor, Electrical
- 2FBE (12222) - Fuel Pressure After Motor Stop
- 2FBF (12223) - Fuel Pressure at Injection Release
- 30BE (12478) - Injector, Calibration Plausibility
- 2AAF (10927) - Fuel Pump Plausibility
Most of these codes indicate an issue with either the HPFP, LPFP, and/or injectors. We'll break down each code below with additional analysis.
N54 29DC (10716) Fault Code
The cylinder injection switch-off code indicates the N54 is not flowing enough fuel. These codes are common with HPFP issues - a well documented problem on the N54. Data-logging is extremely helpful if you are getting this code. LPFP issues may also cause 29DC codes. Data-logs would help track down the issue as you can read fuel pressures and determine whether the high pressure or low pressure pump is to blame.
N54 29E0 (10720) Fault Code
Fuel mixture control 1 indicates you are having air/fuel (AFR) mix issues on bank 1 (cylinders 1-3). Fault code 29E0 can be a tuning related or hardware issue. Faulty O2 sensors may trigger fuel mixture control 1 codes. Fuel injectors are another common problem that triggers this code.
If you're getting this code along with 29E1 (fuel mixture control 2) then you've got AFR issues on both banks. It's unlikely you have a hardware problem on bank 1 and bank 2. In other words, both codes combined likely indicate a tuning issue.
N54 29E1 (10721) Fault Code
Fuel mixture control 2 indicates ARF issues on bank 2 (cylinders 4-6). Refer to fault code 29E0 above. 29E0 and 29E1 are the same code; they simply point to different banks.
N54 29E2 (10722) Fault Code
Fault 29E2 points to the fuel injection rail pressure sensor signal. The sensor itself may potentially be going bad. However, more likely, this code indicates an issue with the N54's HPFP or LPFP. Again, data-logging is a huge help for diagnosing this issue. Check fuel pressures for the high and low pressure pumps. If both pumps check out then you probably have a different issue, such as the sensor.
N54 29F3 (10739) Fault Code
Code 29F3 is related to an issue with the fuel pressure sensor, electrical. As the short code description suggests, this is usually a fault with the low pressure fuel pump sensor. A handful of N54 owners experienced this code but left it alone as the engines were running totally fine. We would personally take this opportunity to upgrade the low pressure fuel pump for higher E85 mixtures.
N54 2FBE (12222) Fault Code
Fault 2FBE indicates an issue with the pressure in the fuel rail once the N54 is shut off. Often, you can simply clear this code and it will not come back. However, if code 2FBE continues popping up it may be an early sign of a failing HPFP. It may also indicate an issue with the LPFP. Pay attention for other codes that may confirm there is an issue going on. A random 2FBE code that doesn't come back was likely just a fluke.
N54 2FBF (12223) Fault Code
A fuel pressure at injection release code (2FBF) is likely another sign of a failing N54 high pressure fuel pump. If you're experiencing long cranks, limp mode, and getting code 2FBF it's likely only time before the HPFP gives out.
N54 30BE (12478) Fault Code
Injector, calibration plausibility typically points to fuel injector issues on the N54. Fortunately, this code may simply indicate something with the calibration is wrong. The injectors must be properly coded to the DME and may throw code 30BE if they are not properly calibrated. You can check the N54 injector calibration with an INPA cable or take it to a repair shop.
N54 2AAF (10927) Fault Code
2AAF fuel pump plausibility is a common fault code on the N54. Fortunately, this code can usually be ignored. Clear the code and check if it comes back. 2AAF pops up most frequently on tuned and modded N54 engines. If associated codes appear with it then revert to confirming operation of high pressure and low pressure fuel pumps.
BMW N54 O2 Sensor Fault Codes
**The post catalytic converter O2 sensors are still VERY IMPORTANT even if you are running catless downpipes. N54 O2 sensors calculate lambda and all of the sensors rely on each other for proper calibration. Do not ignore faulty post-cat O2 sensors even if you are running catless downpipes. You will likely experience lean conditions which is a recipe for blown motors, especially on aggressive tunes.
Below is a list of fault codes commonly related to the N54's oxygen (O2) sensors:
- 2C2B (11307) - Lambda probe in front of catalytic converter, system check
- 2C2C (11308) - Lambda probe in froont of catalytic converter 2, system check
- 2C31 (11313) - Lamba probe in front of cat 1, trimming control
- 2C32 (11314) - Lamba probe in front of cat 2, trimming control
- 2C33 (11315) -
- 2C3C (11324) - lambda probe in front of catalytic converter, not plugged
- 2C3D (11325) - Lambda probe in front of catalytic converter, control failure
- 2C62 (11362) -
- 2C6A (11370) - lambda probe behind catalytic converter, muddled
- 2C6B (11371) - Lambda probe behind catalytic converter, system check
- 2C3E 11372 - Lambda probe in front of catalytic converter 2, control failure or cable transmission failure?
- 2C73 11379 -
- 2C74 11380 - Lambda probe behind catalytic converter 2, signal
- 2C7B (11387) - Lambda probe behind catalytic converter, signal
- 2C7C (11388) - Lambda probe behind catalytic converter 2, signal
- 2C7E (11390) - Lambda probe behind catalytic converter, trimming control
- 2C7F (11391) - Lambda probe behind catalytic converter, trimming control
- 2CAB (11431) - Lambdaprobe 2 before catalyst, temperature
- 2CA7 (11435) - Lambda probe heating in front of catalytic converter 2, function
As you can see, this is one heck of a list. Rather than breaking down each code we will discuss the codes generically below in the "fault code fix" section.
N54 Oxygen Sensor Fault Code Fixes
First off, the N54 will throw fault codes if you have catless downpipes installed. These codes are irrelevant and should be hidden by the tune. You'll want to pay attention to air/fuel ratios (AFR's) if you are experiencing any of the above O2 sensor codes. Faulty O2 sensors will almost always cause lean issues. Running lean is not something you want, especially when running aggressive tunes and boost.
If you are experiencing any of these fault codes and AFR's look OK then you can likely simply clear the codes. If you're AFR's are too lean or too rich then you'll want to look into the O2 sensor(s) being faulty. How do you know which O2 sensor is faulty?
Each O2 sensor code on the N54 will point you in the direction. If a number is not specified then it is referring to bank 1 (cylinders 1-3). The number 2 indicates the issue in confined to bank 2 (cylinders 4-6). Additionally, the code will tell you if the issue is in front of the cat (pre cat) or after the cat (post cat).
Once you have narrowed down the O2 sensor(s) at fault you can physically inspect them. Confirm all wiring is connected. If everything checks out then it's time for new sensor(s).
BMW N54 Turbo & Boost Fault Codes
Below we will discuss a few common fault codes related to the turbochargers and waste-gates:
- 30FF (12543) - Exhaust fume turbocharger low side (underboost)
- 30FE (12542) - Exhaust fume turbocharger, high pressure side (overboost)
- 3100 (12544) - Boost-pressure control, deactivation
- 30CF (12495) - Wastegate, input signal
N54 30FF (12543) Fault Code
This turbo underboost fault code is so common on the N54 that we wrote an entire post about it. Check it out here.
N54 30FE (12542) Fault Code
Code 30FE points to turbocharger over-boost on the N54. Often, this may come down to tuning related issues and dialing in boost more appropriately. Exactly how to accomplish this depends greatly on the tune you're running. If it's not related to tuning then you likely have an issue with boost solenoids or waste-gate springs. Fortunately, the waste-gate is designed to fail in the open position as to not over spin the turbo (this would cause the 30FF under-boost rather than 30FE overboost code). As such, a 30FE code is unlikely to be due to waste-gate failure.
However, the waste-gate springs may need to be properly calibrated. Additionally, the boost solenoids may be applying to much pressure to the waste-gate arms. In order, we recommend checking any potential tuning related causes of over-boost. Next, look into possible boost solenoid issues. If all else fails then the waste-gates may require re-calibration.
N54 3100 (12544) Fault Code
Code 3100 on the N54 refers to boost pressure control deactivation. This code frequently pops up with limp mode and another along with it. For example, if your N54 is severely overheating then the engine will go into limp mode. Turbochargers create a lot of heat so obviously limp mode would want to cut turbocharger operation. As such, this will cause a 3100 fault code.
If code 3100 pops up without any other codes and without limp mode or reduced power mode then try clearing codes. It's rare for this code to pop up by itself. However, if it does happen, simply clear the code and pay attention to see if it comes back with any additional codes or issues.
N54 30CF (12495) Fault Code
The most common cause of 30CF codes is that the N54 waste-gate connection is physically unplugged. Check the DME wiring, especially if running a piggyback tune. It is possible the wires disconnected or became lose. If no connections appear loose then it is possible the piggyback tune board is not working properly.