P02B7 Cylinder 8 Fuel Trim at Min Limit
OBD-II Trouble Code Technical Description
Cylinder 8 Fuel Trim at Min Limit
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC) and typically applies to all gasoline OBD-II vehicles. That may include but is not limited to vehicles from Mazda, Land Rover, Jaguar, Subaru, Ford, BMW, Dodge, etc. Although generic, the exact repair steps may vary depending on year, make, model and powertrain configuration.
A stored P02B7 code means that the powertrain control module (PCM) has detected an extremely rich condition in a specific engine cylinder, in this case it's cylinder #8.
The PCM utilizes the fuel trim system to increase or decrease fuel delivery as required. Input signals from the oxygen sensors provide the PCM with the data required to adjust fuel trim. The PCM uses variations in fuel injector pulse width modulation to effect air/fuel ratio changes.
Short term fuel trim is calculated constantly by the PCM. It fluctuates rapidly and is one of the key factors in calculating long term fuel trim. Every vehicle has minimum and maximum fuel trim percentage parameters programmed into the PCM. The parameters for short term fuel trim are much broader than the parameter specifications for long term fuel trim.
Small variations in fuel trim, typically measured in positive or negative percentage, are normal and will not cause a code P02B7 to be stored. Maximum fuel trim parameters (positive or negative) are normally in the twenty-five-percent range. Once this maximum threshold has been exceeded, a code of this type will be stored.
When the engine is functioning at optimum efficiency and there is little need to increase or decrease the amount of fuel delivered to each cylinder, fuel trim should reflect between zero and ten percent. When lean exhaust conditions are detected by the PCM, fuel must be increased and fuel trim will reflect a positive percentage. If the exhaust is too rich, the engine needs less fuel and fuel trim should reflect a negative percentage.
See also: Everything you want to know about fuel trims.
OBD-II vehicles will need to establish a pattern for long term fuel trim strategy and this will require multiple ignition cycles.
Fuel trim graphs as shown by OBD-II scan tool:
What is the severity of this DTC?
The P02B7 should be classified as severe because a rich fuel condition may lead to numerous drivability issues and catalytic converter damage.
What are some of the symptoms of the code?
Symptoms of a P02B7 trouble code may include:
Diminished engine performance Reduced fuel efficiency Delayed engine startup The presence of stored rich exhaust codes Misfire codes may also be storedWhat are some of the common causes of the code?
Causes for this P02B7 fuel trim code may include:
Defective fuel injector Bad fuel pressure regulator Faulty oxygen sensor Mass air flow (MAF) or Manifold Air Pressure (MAP) sensor failureWhat are some P02B7 troubleshooting steps?
If there are MAF or MAP related codes present, diagnose and repair those before attempting to diagnose this P02B7 code.
I would begin my diagnosis with a general inspection of the fuel injection rail area. My focus would be on the fuel pressure regulator and the vacuum source for the fuel pressure regulator (if applicable). I would check the regulator for signs of leakage. If there is gas on the inside or ooutside of the regulator, suspect that it has failed.
If no obvious mechanical issues are discovered in the engine bay, there are several tools that will be required to continue your diagnosis:
A diagnostic scanner A digital volt/ohmmeter (DVOM) A fuel pressure gauge with adapters A reliable vehicle information sourceNext, I would connect the scanner to the vehicle diagnostic port. I would retriev
Read: 42
