P2177 System Too Lean Off Idle Bank 1
OBD-II Trouble Code Technical Description
System Too Lean Off Idle Bank 1
What does that mean?
This generic powertrain/engine diagnostic trouble code typically applies to fuel injected engines from most European and Asian manufacturers since 2010.
Those manufacturers include but are not limited to Volkswagen, Audi, Mercedes, BMW/Mini, Hyundai, Mazda, Kia and Infiniti. You may also see it on other makes such as Dodge.
This code is mostly concerned about the value provided by the air/fuel ratio sensor, more commonly called an oxygen sensor (located in the exhaust) which helps the vehicle’s PCM (powertrain control module) control the amount of fuel being injected into the engine. Specifically, the PCM is detecting a lean condition which means too much air in the air/fuel ratio. This code is set for Bank 1, which is the bank of cylinders that includes cylinder number 1. This can be a mechanical or an electrical circuit fault, depending upon vehicle manufacturer and fuel system.
Troubleshooting steps may vary depending upon manufacturer, type of fuel system, type of mass airflow sensor (MAF) and wire colors and type of air/fuel ratio sensor/oxygen sensor (AFR/O2) and wire colors.
Symptoms
Symptoms of a P2177 engine code may include:
Causes
Potential causes for this code to set are:
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) for your particular vehicle. Your issue may be a known issue with a known fix put out by the manufacturer and can save you time and money during diagnosis.
First, note if there are any other diagnostic fault codes. If any of them are fuel/fuel system related, diagnose them first. Misdiagnosis has been known to occur if a technician diagnoses this code before any fuel related system codes have been thoroughly diagnosed and dismissed. Insure there are no intake or exhaust leaks. An intake leak, or vacuum leak, makes the engine run lean. An exhaust leak gives the impression of a lean running engine by the AFR/O2 sensor.
Next, locate both the air/fuel ratio sensor/oxygen sensor and the mass airflow sensor on your particular vehicle. Here is an example of a MAF sensor:
Once located, visually inspect the connectors and wiring. Look for chafing, rubbing, bare wires, burn spots or melted plastic. Pull the connectors apart and carefully inspect the terminals (the metal parts) inside the connectors. See if they look corroded, burnt or possibly green in color versus the normal metal color you are probably used to seeing. You can get some Electrical Contact cleaner at any parts store if cleaning of the terminals is needed. If this is not possible, find some 91% rubbing alcohol and a light plastic bristle brush to clean them with. Afterwards let them air dry, get some dielectric silicone compound (same stuff they use for light bulb sockets and spark plug wires) and put some where the terminals come into contact.
If you have a scan tool, clear the diagnostic trouble codes from memory, and see if this code returns. If it does not, then the connections were most likely your problem.
If the code does return, we will need to test the MAF sensor voltage signal to the PCM. Monitor MAF sensor voltage on your scan tool. If a scan tool is not available, then test the signal coming from the MAF sensor with a digital volt ohm meter (DVOM). With the sensor connected, the red voltmeter lead should be attached to the MAF sensor signal wire and the black voltmeter lead connected to ground. Start the engine and monitor the MAF sensor input. As engine RPM is increased, the MAF sensor signal should increase. Check the manufacturer’s specifications, as there may be a chart informing you of what the voltage should be at a given RPM. If it fails this test, replace the MAF sensor and retest.
If the prior tests have passed and the code is still present, monitor the air/fuel ratio sensor/oxygen sensor (AFR/O2). If it continually indicates that the engine is running lean, locate any and all possibilities that could cause a lean running engine. These include:
Again, it cannot be stressed enough that all other codes must be diagnosed prior to this one, as issues that cause other codes to set can also cause this one to set as well.
Need help?
Let us fix your problem. You are most welcome our diagnosis experts have in most cases the knowledge and skills to find the cause of the error code p2177 and to solve the problems.
Make an appointment for diagnosis
"Delete Error Code Permanently, Disable DTC Error Code Function for p2177 in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p2177 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p2177.
