Fault code P029E – fuel trim, cylinder 2 maximum control limit reached

Fault code P029E is called “Fuel Trim (FT), Cylinder 2 Maximum Control Limit Reached” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P029E

This diagnostic trouble code is a common one that applies to all gasoline vehicles with OBD-II system. However, the exact steps to clear Error P029E may vary depending on the powertrain configuration.

The PCM uses the fuel adjustment system to adjust the fuel-air mixture entering the engine cylinders. The short-term adjustment is calculated by the PCM continuously, based on the minimum and maximum fuel-to-air ratio parameters.

Small deviations are normal and will not cause the P029E code to persist. The maximum fuel adjustment parameters are normally in the range of twenty-five percent. Exceeding this maximum threshold, causes this type of code to persist.

The engine operates at optimum efficiency when the minimum and maximum fuel-air mixture parameters are between zero and ten percent. These parameters are set in the vehicle’s PCM and may vary from vehicle to vehicle.

If the PCM detects lean exhaust, the amount of fuel must be increased, in which case the fuel correction will reflect a positive percentage. If the exhaust is too rich, the engine needs less fuel and the fuel control should reflect a negative percentage.

Code P029E means that the Powertrain Control Module (PCM) has detected an extremely low fuel level in a specific engine cylinder, in this case it is cylinder #2.

Symptoms of vehicle malfunctions

The main signal that an error P029E has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

1. The “Check engine” indicator light on the control panel will illuminate (the code will be stored in the ECM memory as a fault).
2. Floating revolutions, the vehicle engine may run erratically.
3. Reduced engine power.
4. Engine stalls or starts poorly.
5. Twitch/ignition skips at idle or under load.
6. Presence of stored lean mixture codes in the exhaust.
7. Ignition skip codes may be present.

The severity of the P029E error is high, you should take action to correct it as soon as possible. As the vehicle may have serious problems potentially affecting engine performance.

Factors that can cause this error code

The error code P029E can mean that one or more of the following problems have occurred:

• Faulty or leaking fuel injector.
• A bad fuel pump.
• Engine vacuum leak (including EGR valve failure).
• Faulty oxygen sensor.
• Faulty mass air flow (MAF) or manifold air pressure (MAP) sensor.
• Sometimes caused by a faulty ECM module.

How to fix or reset OBD-2 code P029E

Some suggested steps for troubleshooting and fix the error code P029E:

1. Read all stored data and error codes with an OBD-II scan tool.
2. Clear the error codes from the computer memory.
3. Test drive the vehicle to see if error P029E reappears.
4. Check the operation of the fuel injectors.
5. Check the vacuum leak and the EGR valve.
6. Test the oxygen sensor, mass airflow sensor, and manifold air pressure.
7. If no problems are found, check the engine control module (ECM).

Diagnose and repair of problems

Start fixing error P029E by performing a full system scan for all OBD2 fault codes. If codes related to MAF or MAP sensor errors are present, fix them first before moving on to fixing the main error.

Continue your diagnosis with a general inspection of the engine intake manifold area and pay attention to the vacuum leak. Listen for hissing sounds that may indicate a leak.

Check all hoses and plastic lines for cracks or breaks. Inspect the edges of the intake manifold for signs of gasket failure. Also inspect the fuel injectors for signs of fuel leakage. If the injector is wet from fuel, you can assume that it has failed.

Check the oxygen sensor and fuel pump

Monitor the oxygen sensor to determine if a lean exhaust condition actually exists. If a lean exhaust condition is detected, use a fuel pressure gauge to check the fuel pressure and compare it to the manufacturer’s specifications.

If the fuel pressure is below the minimum values, use a multimeter to check the relay and voltage at the fuel pump. Normally, it should match the voltage that the battery provides.

If the voltage is normal, remove the fuel filter and check for debris, if it is clogged, replace it. If the filter is clean, the fuel pump should be tested for problems.

Check the wiring harness and injectors

After checking the fuel pressure, if it meets specifications, check the wiring harness for fraying and the connector for loose contacts or a broken lock. Repair if necessary and check to see if the P029E error returns.

Disconnect the PCM connector and connect to the fuel injector driver circuit. Any resistance indicates a problem. An infinite resistance indicates a break in the circuit. Locate and repair, then try again.

If you can’t find any problems with the harness but the fuel injector driver doesn’t work, check the PCM power and ground. If they are fine, the PCM itself may be faulty.

If the electrical part is good, the injector itself is most likely clogged or dirty. Try to clean it, a flushing kit is inexpensive, which will also help the rest of the injectors work better. If flushing does not solve the problem, the injector needs to be replaced.

On which vehicles does this problem occur most frequently

Fault code P029E can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

• BMW
• Ford
• Land Rover
• Mercedes-Benz
• Peugeot

Fault code P029E can sometimes be found with other errors. The most common are the following: P029A, P02A2, P02A6, P02AA, P02AE, P02B2, P02B6, P02BA, P02BE, P02C2, P02C6.

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